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| author | cinap_lenrek <cinap_lenrek@gmx.de> | 2012-06-06 22:28:48 +0200 |
|---|---|---|
| committer | cinap_lenrek <cinap_lenrek@gmx.de> | 2012-06-06 22:28:48 +0200 |
| commit | 1bbdbb2828dc3642df0b452ef9d1685dc278ae79 (patch) | |
| tree | 437db5fe8333ebd061d0edc72e5caef293170670 /sys/doc/acme | |
| parent | 1ffd5f9af1ee4c870346a482fee2dc2d9314dba4 (diff) | |
/sys/doc: remove autogenerated postscript files
Diffstat (limited to 'sys/doc/acme')
| -rw-r--r-- | sys/doc/acme/acme.html | 1466 |
1 files changed, 0 insertions, 1466 deletions
diff --git a/sys/doc/acme/acme.html b/sys/doc/acme/acme.html deleted file mode 100644 index 4ebe9158d..000000000 --- a/sys/doc/acme/acme.html +++ /dev/null @@ -1,1466 +0,0 @@ -<?xml version="1.0" encoding="utf-8"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" -"http://www.w3.org/TR/html4/loose.dtd"> -<html> -<head> -<meta http-equiv=Content-Type content="text/html; charset=utf8"> -<title>Acme: A User Interface for Programmers</title> -</meta> -</head> -<body> -<p style="margin-top: 0; margin-bottom: 0.50in"></p> -<p style="margin-top: 0; margin-bottom: 0.21in"></p> - -<p style="line-height: 1.4em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: center;"> -<span style="font-size: 12pt"><b>Acme: A User Interface for Programmers</b></span></p> -<p style="margin-top: 0; margin-bottom: 0.21in"></p> - -<p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.4em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: center;"> -<span style="font-size: 10pt"><i></i></span><span style="font-size: 10pt"><i>Rob Pike</i></span><span style="font-size: 10pt"><i></i></span></p> -<p style="line-height: 1.4em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: center;"> -<span style="font-size: 10pt"><i></i></span><span style="font-size: 10pt"><i>rob@plan9.bell-labs.com</i></span><span style="font-size: 10pt"><i></i></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="margin-top: 0; margin-bottom: 0.33in"></p> -<p style="line-height: 1.4em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: center;"> -<span style="font-size: 10pt"><i>ABSTRACT</i></span></p> -<p style="margin-top: 0; margin-bottom: 0.19in"></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="line-height: 1.2em; margin-left: 1.50in; text-indent: 0.00in; margin-right: 1.50in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">A hybrid of window system, shell, and editor, Acme gives text-oriented -applications a clean, expressive, and consistent style of interaction. -Traditional window systems support interactive client programs and offer libraries of -pre-defined operations such as pop-up menus -and buttons to promote a consistent -user interface among the clients. -Acme instead provides its clients with a fixed user interface and -simple conventions to encourage its uniform use. -Clients access the facilities of Acme through a file system interface; -Acme is in part a file server that exports device-like files that may be -manipulated to access and control the contents of its windows. -Written in a concurrent programming language, -Acme is structured as a set of communicating processes that neatly subdivide -the various aspects of its tasks: display management, input, file server, and so on. -</span><span style="font-size: 10pt"></span><span style="font-size: 10pt"></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.50in; text-indent: 0.35in; margin-right: 1.50in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme attaches distinct functions to the three mouse buttons: -the left selects text; -the middle executes textual commands; -and the right combines context search and file opening -functions to integrate the various applications and files in -the system. -</span><span style="font-size: 10pt"></span><span style="font-size: 10pt"></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.50in; text-indent: 0.35in; margin-right: 1.50in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme works well enough to have developed -a community that uses it exclusively. -Although Acme discourages the traditional style of interaction -based on typescript windows—teletypes—its -users find Acme’s other services render -typescripts obsolete. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="margin-top: 0; margin-bottom: 0.50in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>History and motivation -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The usual typescript style of interaction with -Unix and its relatives is an old one. -The typescript—an intermingling of textual commands and their -output—originates with the scrolls of paper on teletypes. -The advent of windowed terminals has given each user what -amounts to an array of teletypes, a limited and unimaginative -use of the powers of bitmap displays and mice. -Systems like the Macintosh -that do involve the mouse as an integral part of the interaction -are geared towards general users, not experts, and certainly -not programmers. -Software developers, at least on time-sharing systems, have been left behind. -</span></p><center><table width=60% cellspacing=0 cellpadding=0 border=0><tr height=1> <td width=1 bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td width=1 bgcolor=#000000 /></tr><tr height=10> <td width=1 bgcolor=#000000 /> <td width=10 /> <td /> <td width=10 /> <td width=1 bgcolor=#000000 /></tr> -<tr> -<td width=1 bgcolor=#000000 /><td width=10 /><td> -<center><a href="acme.fig1.gif"><img src="acme.fig1.gif" /></a></center> -<p style="line-height: 1.2em; text-indent: 0.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Figure 1. A small Acme screen—normally it runs on a larger display—demonstrating -some of the details discussed in the text. -The right column contains some guide files, -a mailbox presented by Acme’s mail program, -the columnated display of files in Acme’s own source directory, -a couple of windows from the OED browser, -a debugger window, -and an error window showing diagnostics from a compilation. -The left column holds a couple of source files -(</span><span style="font-size: 10pt"><tt>dat.h</tt></span><span style="font-size: 10pt"> -and -</span><span style="font-size: 10pt"><tt>acme.l</tt></span><span style="font-size: 10pt">), -another debugger window displaying a stack trace, -and a third source file -(</span><span style="font-size: 10pt"><tt>time.l</tt></span><span style="font-size: 10pt">). -</span><span style="font-size: 10pt"><tt>Time.l</tt></span><span style="font-size: 10pt"> -was opened from the debugger by clicking the right mouse button -on a line in the stack window; -the mouse cursor landed on the offending line of -</span><span style="font-size: 10pt"><tt>acme.l</tt></span><span style="font-size: 10pt"> -after a click on the compiler message. -</span></p></td> -<td width=10 /><td width=1 bgcolor=#000000 /> -</tr> -<tr height=10><td width=1 bgcolor=#000000 /> <td width=10 /><td /><td width=10 /> <td width=1 bgcolor=#000000 /></tr><tr height=1> <td width=1 bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td width=1 bgcolor=#000000 /></tr> -</table></center> -<p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Some programs have mouse-based editing of -text files and typescripts; -ones I have built include -the window systems -</span><span style="font-size: 10pt"><tt>mux</tt></span><span style="font-size: 10pt"> -[Pike88] -and -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -[Pike91] -and the text editor -Sam [Pike87]. -These have put the programmer’s mouse to some productive work, -but not wholeheartedly. Even experienced users of these programs -often retype text that could be grabbed with the mouse, -partly because the menu-driven interface is imperfect -and partly because the various pieces are not well enough integrated. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Other programs—EMACS [Stal93] is the prime example—offer a high -degree of integration but with a user interface built around the -ideas of cursor-addressed terminals that date from the 1970’s. -They are still keyboard-intensive and -dauntingly complex. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The most ambitious attempt to face these issues was the Cedar -system, developed at Xerox [Swei86]. -It combined a new programming language, compilers, -window system, even microcode—a complete system—to -construct a productive, highly -integrated and interactive environment -for experienced users of compiled languages. -Although successful internally, the system was so large -and so tied to specific hardware that it never fledged. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Cedar was, however, the major inspiration for Oberon [Wirt89], -a system of similar scope but much smaller scale. -Through careful selection of Cedar’s ideas, Oberon shows -that its lessons can be applied to a small, coherent system -that can run efficiently on modest hardware. -In fact, Oberon probably -errs too far towards simplicity: a single-process system -with weak networking, it seems an architectural throwback. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme is a new program, -a combined window system, editor, and shell, -that applies -some of the ideas distilled by Oberon. -Where Oberon uses objects and modules within a programming language (also called Oberon), -Acme uses files and commands within an existing operating system (Plan 9). -Unlike Oberon, Acme does not yet have support for graphical output, just text. -At least for now, the work on Acme has concentrated on -producing the smoothest user interface possible for a programmer -at work. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The rest of this paper describes Acme’s interface, -explains how programs can access it, -compares it to existing systems, -and finally presents some unusual aspects of its implementation. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>User interface -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<center><table width=60% cellspacing=0 cellpadding=0 border=0><tr height=1> <td width=1 bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td width=1 bgcolor=#000000 /></tr><tr height=10> <td width=1 bgcolor=#000000 /> <td width=10 /> <td /> <td width=10 /> <td width=1 bgcolor=#000000 /></tr> -<tr> -<td width=1 bgcolor=#000000 /><td width=10 /><td> -<center><a href="acme.fig2.gif"><img src="acme.fig2.gif" /></a></center> -<p style="line-height: 1.2em; text-indent: 0.35in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Figure 2. An Acme window showing a section of code. -The upper line of text is the tag containing the file name, -relevant commands, and a scratch area (right of the vertical bar); -the lower portion of the window is the -body, or contents, of the file. -Here the scratch area contains a command for the middle button -(</span><span style="font-size: 10pt"><tt>mk</tt></span><span style="font-size: 10pt">) -and a word to search for with the right button -(</span><span style="font-size: 10pt"><tt>cxfidalloc</tt></span><span style="font-size: 10pt">). -The user has just -clicked the right button on -</span><span style="font-size: 10pt"><tt>cxfidalloc</tt></span><span style="font-size: 10pt"> -and Acme has searched for the word, highlighted it, -and moved the mouse cursor there. The file has been modified: -the center of the layout box is black and the command -</span><span style="font-size: 10pt"><tt>Put</tt></span><span style="font-size: 10pt"> -appears in the tag. -</span></p></td> -<td width=10 /><td width=1 bgcolor=#000000 /> -</tr> -<tr height=10><td width=1 bgcolor=#000000 /> <td width=10 /><td /><td width=10 /> <td width=1 bgcolor=#000000 /></tr><tr height=1> <td width=1 bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td bgcolor=#000000 /> <td width=10 bgcolor=#000000 /> <td width=1 bgcolor=#000000 /></tr> -</table></center> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme windows are arrayed in columns (Figure 1) and are used more -dynamically than in an environment like X Windows or -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -[Sche86, Pike91]. -The system frequently creates them automatically and the user -can order a new one with a single mouse button click. -The initial placement of a new window is determined -automatically, but the user may move an existing window anywhere -by clicking or dragging a -</span><span style="font-size: 10pt"><i>layout box</i></span><span style="font-size: 10pt"> -in the upper left corner of -the window. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme windows have two parts: a -</span><span style="font-size: 10pt"><i>tag</i></span><span style="font-size: 10pt"> -holding a single line of text, -above a -</span><span style="font-size: 10pt"><i>body</i></span><span style="font-size: 10pt"> -holding zero or more lines (Figure 2). -The body typically contains an image of a file being edited -or the editable output of a -program, analogous to an -EMACS shell -window. The tag contains -the name of the window -(usually the name of the associated -file or directory), some built-in commands, and a scratch area to hold arbitrary text. -If a window represents a directory, the name in the tag ends with -a slash and the body contains a list of the names of the files -in the directory. -Finally, each non-empty body holds a scroll bar at the left of the text. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Each column of windows also has a layout box and a tag. -The tag has no special meaning, although Acme pre-loads it with a few -built-in commands. -There is also a tag across the whole display, also loaded with -helpful commands and a list of active processes started -by Acme. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Typing with the keyboard and selecting with the left button are as in -many other systems, including the Macintosh, -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt">, -and Sam. -The middle and right buttons are used, somewhat like the left button, -to ‘sweep’ text, but the indicated text is treated in a way -that depends on the text’s location—</span><span style="font-size: 10pt"><i>context</i></span><span style="font-size: 10pt">—as well as its content. -This context, based on the directory of the file containing the text, -is a central component of Acme’s style of interaction. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme has no single notion of ‘current directory’. -Instead, every command, file name, -action, and so on is interpreted or executed in the directory named by the -tag of the window containing the command. For example, the string -</span><span style="font-size: 10pt"><tt>mammals</tt></span><span style="font-size: 10pt"> -in a window labeled -</span><span style="font-size: 10pt"><tt>/lib/</tt></span><span style="font-size: 10pt"> -or -</span><span style="font-size: 10pt"><tt>/lib/insects</tt></span><span style="font-size: 10pt"> -will be interpreted as the file name -</span><span style="font-size: 10pt"><tt>/lib/mammals</tt></span><span style="font-size: 10pt"> -if such a file exists. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Throughout Acme, the middle mouse button is used to execute commands -and the right mouse button is used to locate and select files and text. -Even when there are no true files on which to operate—for example -when editing mail messages—Acme and its applications use -consistent extensions of these basic functions. -This idea is as vital to Acme as icons are to the Macintosh. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The middle button executes commands: text swept with the button -pressed is underlined; when the button is released, the underline is -removed and the indicated text is executed. -A modest number of commands are recognized as built-ins: words like -</span><span style="font-size: 10pt"><tt>Cut</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>Paste</tt></span><span style="font-size: 10pt">, -and -</span><span style="font-size: 10pt"><tt>New</tt></span><span style="font-size: 10pt"> -name -functions performed directly by Acme. -These words often appear in tags to make them always available, -but the tags are not menus: any text anywhere in Acme may be a command. -For example, in the tag or body of any window one may type -</span><span style="font-size: 10pt"><tt>Cut</tt></span><span style="font-size: 10pt">, -select it with the left button, use the middle button to execute it, -and watch it disappear again. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">If the middle button indicates a command that is not recognized as a built-in, -it is executed in the directory -named by the tag of the window holding the text. -Also, the file to be executed is searched for first in that directory. -Standard input is connected to -</span><span style="font-size: 10pt"><tt>/dev/null</tt></span><span style="font-size: 10pt">, -but standard and error outputs are connected to an Acme window, -created if needed, called -</span><span style="font-size: 10pt"><i>dir</i></span><span style="font-size: 10pt"><tt>/+Errors</tt></span><span style="font-size: 10pt"> where -</span><span style="font-size: 10pt"><i>dir</i></span><span style="font-size: 10pt"> -is the directory of the window. -(Programs that need interactive input use a different interface, described below.) -A typical use of this is to type -</span><span style="font-size: 10pt"><tt>mk</tt></span><span style="font-size: 10pt"> -(Plan 9’s -</span><span style="font-size: 10pt"><tt>make</tt></span><span style="font-size: 10pt">) -in the scratch area in the tag of a C source window, say -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/regexp.c</tt></span><span style="font-size: 10pt">, -and execute it. -Output, including compiler errors, appears in the window labeled -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/+Errors</tt></span><span style="font-size: 10pt">, -so file names in the output are associated with the windows and directory -holding the source. -The -</span><span style="font-size: 10pt"><tt>mk</tt></span><span style="font-size: 10pt"> -command remains in the tag, serving as a sort of menu item for the associated -window. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Like the middle button, the right button is used to indicate text by sweeping it out. -The indicated text is not a command, however, but the argument of a generalized -search operator. -If the text, perhaps after appending it to the directory of the window containing it, -is the name of an existing file, Acme creates a new window to hold the file -and reads it in. It then moves the mouse cursor to that window. If the file is -already loaded into Acme, the mouse motion happens but no new window is made. -For example, indicating the string -</span><span style="font-size: 10pt"><tt>sam.h</tt></span><span style="font-size: 10pt"> -in -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>#include "sam.h"</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">in a window on the file -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/regexp.c</tt></span><span style="font-size: 10pt"> -will open the file -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/sam.h</tt></span><span style="font-size: 10pt">. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">If the file name is followed immediately by a colon and a legal address in -Sam notation (for example a line number or a regular expression delimited in -slashes or a comma-separated compound of such addresses), Acme highlights -the target of that address in the file and places the mouse there. One may jump to -line 27 of -</span><span style="font-size: 10pt"><tt>dat.h</tt></span><span style="font-size: 10pt"> -by indicating with the right button the text -</span><span style="font-size: 10pt"><tt>dat.h:27</tt></span><span style="font-size: 10pt">. -If the file is not already open, Acme loads it. -If the file name is null, for example if the indicated string is -</span><span style="font-size: 10pt"><tt>:/^main/</tt></span><span style="font-size: 10pt">, -the file is assumed to be that of the window containing the string. -Such strings, when typed and evaluated in the tag of a window, amount to -context searches. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">If the indicated text is not the name of an existing file, it is taken to be literal -text and is searched for in the body of the window containing the text, highlighting -the result as if it were the result of a context search. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">For the rare occasion when a file name -</span><span style="font-size: 10pt"><i>is</i></span><span style="font-size: 10pt"> -just text to search for, it can be selected with the left button and used as the -argument to a built-in -</span><span style="font-size: 10pt"><tt>Look</tt></span><span style="font-size: 10pt"> -command that always searches for literal text. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Nuances and heuristics -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">A user interface should not only provide the necessary functions, it should also -</span><span style="font-size: 10pt"><i>feel</i></span><span style="font-size: 10pt"> -right. -In fact, it should almost not be felt at all; when one notices a -user interface, one is distracted from the job at hand [Pike88]. -To approach this invisibility, some of Acme’s properties and features -are there just to make the others easy to use. -Many are based on a fundamental principle of good design: -let the machine do the work. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme tries to avoid needless clicking and typing. -There is no ‘click-to-type’, eliminating a button click. -There are no pop-up or pull-down menus, eliminating the mouse action needed to -make a menu appear. -The overall design is intended to make text on the screen useful without -copying or retyping; the ways in which this happens involve -the combination of many aspects of the interface. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme tiles its windows and places them automatically -to avoid asking the user to place and arrange them. -For this policy to succeed, the automatic placement must behave well enough -that the user is usually content with the location of a new window. -The system will never get it right all the time, but in practice most -windows are used at least for a while where Acme first places them. -There have been several complete rewrites of the -heuristics for placing a new window, -and with each rewrite the system became -noticeably more comfortable. The rules are as follows, although -they are still subject to improvement. -The window appears in the ‘active’ column, that most recently used for typing or -selecting. -Executing and searching do not affect the choice of active column, -so windows of commands and such do not draw new windows towards them, -but rather let them form near the targets of their actions. -Output (error) windows always appear towards the right, away from -edited text, which is typically kept towards the left. -Within the column, several competing desires are balanced to decide where -and how large the window should be: -large blank spaces should be consumed; -existing text should remain visible; -existing large windows should be divided before small ones; -and the window should appear near the one containing the action that caused -its creation. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme binds some actions to chords of mouse buttons. -These include -</span><span style="font-size: 10pt"><tt>Cut</tt></span><span style="font-size: 10pt"> -and -</span><span style="font-size: 10pt"><tt>Paste</tt></span><span style="font-size: 10pt"> -so these common operations can be done without -moving the mouse. -Another is a way to apply a command in one window to text (often a file name) -in another, avoiding the actions needed to assemble the command textually. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Another way Acme avoids the need to move the mouse is instead to move the cursor -to where it is likely to be used next. When a new window is made, Acme -moves the cursor to the new window; in fact, to the selected text in that window. -When the user deletes a newly made window, the cursor is -returned to the point it was before the window was made, -reducing the irritation of windows that pop up to report annoying errors. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">When a window is moved, Acme moves the cursor to the layout box in -its new place, to permit further adjustment without moving the mouse. -For example, when a click of the left mouse button on the layout box grows -the window, the cursor moves to the new location of the box so repeated clicks, -without moving the mouse, continue to grow it. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Another form of assistance the system can offer is to supply precision in -pointing the mouse. The best-known form of this is ‘double-clicking’ to -select a word rather than carefully sweeping out the entire word. -Acme provides this feature, using context to decide whether to select -a word, line, quoted string, parenthesized expression, and so on. -But Acme takes the idea much further by applying it to execution -and searching. -A -</span><span style="font-size: 10pt"><i>single</i></span><span style="font-size: 10pt"> -click, that is, a null selection, with either the middle or right buttons, -is expanded automatically to indicate the appropriate text containing -the click. What is appropriate depends on the context. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">For example, to execute a single-word command -such as -</span><span style="font-size: 10pt"><tt>Cut</tt></span><span style="font-size: 10pt">, -it is not necessary to sweep the entire word; just clicking the button once with -the mouse pointing at the word is sufficient. ‘Word’ -means the largest string of likely file name characters surrounding the location -of the click: click on a file name, run that program. -On the right button, the rules are more complicated because -the target of the click might be a file name, file name with address, -or just plain text. Acme examines the text near the click to find -a likely file name; -if it finds one, it checks that it names an existing file (in the directory named in the tag, if the name is relative) -and if so, takes that as the result, after extending it with any address -that may be present. If there is no file with that name, Acme -just takes the largest alphanumeric string under the click. -The effect is a natural overloading of the button to refer to plain text as -well as file names. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">First, though, if the click occurs over the left-button-selected text in the window, -that text is taken to be what is selected. -This makes it easy to skip through the occurrences of a string in a file: just click -the right button -on some occurrence of the text in the window (perhaps after typing it in the tag) -and click once for each subsequent occurrence. It isn’t even necessary to move -the mouse between clicks; Acme does that. -To turn a complicated command into a sort of menu item, select it: -thereafter, clicking the middle button on it will execute the full command. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">As an extra feature, Acme recognizes file names in angle brackets -</span><span style="font-size: 10pt"><tt><></tt></span><span style="font-size: 10pt"> -as names of files in standard directories of include files, -making it possible for instance to look at -</span><span style="font-size: 10pt"><tt><stdio.h></tt></span><span style="font-size: 10pt"> -with a single click. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Here’s an example to demonstrate how the actions and defaults work together. -Assume -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/regexp.c</tt></span><span style="font-size: 10pt"> -is -open and has been edited. We write it (execute -</span><span style="font-size: 10pt"><tt>Put</tt></span><span style="font-size: 10pt"> -in the tag; once the file is written, Acme removes the word from the tag) -and type -</span><span style="font-size: 10pt"><tt>mk</tt></span><span style="font-size: 10pt"> -in the tag. We execute -</span><span style="font-size: 10pt"><tt>mk</tt></span><span style="font-size: 10pt"> -and get some errors, which appear in a new window labeled -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/sam/+Errors</tt></span><span style="font-size: 10pt">. -The cursor moves automatically to that window. -Say the error is -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>main.c:112: incompatible types on assignment to ‘pattern’</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">We move the mouse slightly and click the right button -at the left of the error message; Acme -makes a new window, reads -</span><span style="font-size: 10pt"><tt>/sys/src/cmd/main.c</tt></span><span style="font-size: 10pt"> -into it, selects line 112 -and places the mouse there, right on the offending line. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Coupling to existing programs -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme’s syntax for file names and addresses makes it easy for other programs -to connect automatically to Acme’s capabilities. For example, the output of -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>grep -n variable *.[ch]</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">can be used to help Acme step through the occurrences of a variable in a program; -every line of output is potentially a command to open a file. -The file names need not be absolute, either: the output -appears in a window labeled with the directory in which -</span><span style="font-size: 10pt"><tt>grep</tt></span><span style="font-size: 10pt"> -was run, from which Acme can derive the full path names. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">When necessary, we have changed the output of some programs, -such as compiler error messages, to match -Acme’s syntax. -Some might argue that it shouldn’t be necessary to change old programs, -but sometimes programs need to be updated when systems change, -and consistent output benefits people as well as programs. -A historical example is the retrofitting of standard error output to the -early Unix programs when pipes were invented. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Another change was to record full path names in -the symbol table of executables, so line numbers reported by the debugger -are absolute names that may be used directly by Acme; it’s not necessary -to run the debugger in the source directory. (This aids debugging -even without Acme.) -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">A related change was to add lines of the form -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>#pragma src "/sys/src/libregexp"</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">to header files; coupled with Acme’s ability to locate a header file, -this provides a fast, keyboardless way to get the source associated with a library. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Finally, Acme directs the standard output of programs it runs to -windows labeled by the directory in which the program is run. -Acme’s splitting of the -output into directory-labeled windows is a small feature that has a major effect: -local file names printed by programs can be interpreted directly by Acme. -By indirectly coupling the output of programs to the input, -it also simplifies the management of software that occupies multiple -directories. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Coupling to new programs -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Like many Plan 9 programs, -Acme offers a programmable interface to -other programs by acting as a file server. -The best example of such a file server is the window system -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -[Pike91], -which exports files with names such as -</span><span style="font-size: 10pt"><tt>screen</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>cons</tt></span><span style="font-size: 10pt">, -and -</span><span style="font-size: 10pt"><tt>mouse</tt></span><span style="font-size: 10pt"> -through which applications may access the I/O capabilities of the windows. -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -provides a -</span><span style="font-size: 10pt"><i>distinct</i></span><span style="font-size: 10pt"> -set of files for each window and builds a private file name space -for the clients running ‘in’ each window; -clients in separate windows see distinct files with the same names -(for example -</span><span style="font-size: 10pt"><tt>/dev/mouse</tt></span><span style="font-size: 10pt">). -Acme, like the process file system [PPTTW93], instead associates each -window with a directory of files; the files of each window are visible -to any application. -This difference reflects a difference in how the systems are used: -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -tells a client what keyboard and mouse activity has happened in its window; -Acme tells a client what changes that activity wrought on any window it asks about. -Putting it another way, -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt"> -enables the construction of interactive applications; -Acme provides the interaction for applications. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The root of -Acme’s file system is mounted using Plan 9 operations on the directory -</span><span style="font-size: 10pt"><tt>/mnt/acme</tt></span><span style="font-size: 10pt">. -In -that root directory appears a directory for each window, numbered with the window’s identifier, -analogous to a process identifier, for example -</span><span style="font-size: 10pt"><tt>/mnt/acme/27</tt></span><span style="font-size: 10pt">. -The window’s directory -contains 6 files: -</span><span style="font-size: 10pt"><tt>/mnt/acme/27/addr</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>body</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>ctl</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt">, -and -</span><span style="font-size: 10pt"><tt>tag</tt></span><span style="font-size: 10pt">. -The -</span><span style="font-size: 10pt"><tt>body</tt></span><span style="font-size: 10pt"> -and -</span><span style="font-size: 10pt"><tt>tag</tt></span><span style="font-size: 10pt"> -files contain the text of the respective parts of the window; they may be -read to recover the contents. Data written to these files is appended to the text; -</span><span style="font-size: 10pt"><tt>seeks</tt></span><span style="font-size: 10pt"> -are ignored. -The -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt"> -and -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt"> -files provide random access to the contents of the body. -The -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt"> -file is written to set a character position within the body; the -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt"> -file may then be read to recover the contents at that position, -or written to change them. -(The tag is assumed -small and special-purpose enough not to need special treatment. -Also, -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt"> -indexes by character position, which is not the same as byte offset -in Plan 9’s multi-byte character set [Pike93]). -The format accepted by the -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt"> -file is exactly the syntax of addresses within the user interface, -permitting regular expressions, line numbers, and compound addresses -to be specified. For example, to replace the contents of lines 3 through 7, -write the text -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>3,7</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">to the -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt"> -file, then write the replacement text to the -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt"> -file. A zero-length write deletes the addressed text; further writes extend the replacement. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The control file, -</span><span style="font-size: 10pt"><tt>ctl</tt></span><span style="font-size: 10pt">, -may be written with commands to effect actions on the window; for example -the command -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>name /adm/users</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">sets the name in the tag of the window to -</span><span style="font-size: 10pt"><tt>/adm/users</tt></span><span style="font-size: 10pt">. -Other commands allow deleting the window, writing it to a file, and so on. -Reading the -</span><span style="font-size: 10pt"><tt>ctl</tt></span><span style="font-size: 10pt"> -file recovers a fixed-format string containing 5 textual numbers—the window -identifier, the number of characters in the tag, the number in the body, -and some status information—followed by the text of the tag, up to a newline. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The last file, -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt">, -is the most unusual. -A program reading a window’s -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt"> -file is notified of all changes to the text of the window, and -is asked to interpret all middle- and right-button actions. -The data passed to the program is fixed-format and reports -the source of the action (keyboard, mouse, external program, etc.), -its location (what was pointed at or modified), and its nature (change, -search, execution, etc.). -This message, for example, -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>MI15 19 0 4 time</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">reports that actions of the mouse -(</span><span style="font-size: 10pt"><tt>M</tt></span><span style="font-size: 10pt">) -inserted in the body (capital -</span><span style="font-size: 10pt"><tt>I</tt></span><span style="font-size: 10pt">) -the 4 characters of -</span><span style="font-size: 10pt"><tt>time</tt></span><span style="font-size: 10pt"> -at character positions 15 through 19; the zero is a flag word. -Programs may apply their own interpretations of searching and -execution, or may simply reflect the events back to Acme, -by writing them back to the -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt"> -file, to have the default interpretation applied. -Some examples of these ideas in action are presented below. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Notice that changes to the window are reported -after the fact; the program is told about them but is not required to act -on them. Compare this to a more traditional interface in which a program -is told, for example, that a character has been typed on the keyboard and -must then display and interpret it. -Acme’s style stems from the basic model of the system, in which any -number of agents—the keyboard, mouse, external programs -writing to -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt"> -or -</span><span style="font-size: 10pt"><tt>body</tt></span><span style="font-size: 10pt">, -and so on—may -change the contents of a window. -The style is efficient: many programs are content -to have Acme do most of the work and act only when the editing is completed. -An example is the Acme mail program, which can ignore the changes -made to a message being composed -and just read its body when asked to send it. -A disadvantage is that some traditional ways of working are impossible. -For example, there is no way ‘to turn off echo’: characters appear on the -screen and are read from there; no agent or buffer stands between -the keyboard and the display. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">There are a couple of other files made available by Acme in its root directory -rather than in the directory of each window. -The text file -</span><span style="font-size: 10pt"><tt>/mnt/acme/index</tt></span><span style="font-size: 10pt"> -holds a list of all window names and numerical identifiers, -somewhat analogous to the output of the -</span><span style="font-size: 10pt"><tt>ps</tt></span><span style="font-size: 10pt"> -command for processes. -The most important, though, is -</span><span style="font-size: 10pt"><tt>/mnt/acme/new</tt></span><span style="font-size: 10pt">, -a directory that makes new windows, similar to the -</span><span style="font-size: 10pt"><tt>clone</tt></span><span style="font-size: 10pt"> -directory in the Plan 9 network devices [Pres93]. -The act of opening any file in -</span><span style="font-size: 10pt"><tt>new</tt></span><span style="font-size: 10pt"> -creates a new Acme window; thus the shell command -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>grep -n var *.c > /mnt/acme/new/body</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">places its output in the body of a fresh window. -More sophisticated applications may open -</span><span style="font-size: 10pt"><tt>new/ctl</tt></span><span style="font-size: 10pt">, -read it to discover the new window’s identifier, and then -open the window’s other files in the numbered directory. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Acme-specific programs -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Although Acme is in part an attempt to move beyond typescripts, -they will probably always have utility. -The first program written for Acme was therefore one -to run a shell or other traditional interactive application -in a window, the Acme analog of -</span><span style="font-size: 10pt"><tt>xterm</tt></span><span style="font-size: 10pt">. -This program, -</span><span style="font-size: 10pt"><tt>win</tt></span><span style="font-size: 10pt">, -has a simple structure: -it acts as a two-way intermediary between Acme and the shell, -cross-connecting the standard input and output of the shell to the -text of the window. -The style of interaction is modeled after -</span><span style="font-size: 10pt"><tt>mux</tt></span><span style="font-size: 10pt"> -[Pike88]: standard output is added to the window at the -</span><span style="font-size: 10pt"><i>output point;</i></span><span style="font-size: 10pt"> -text typed after the output point -is made available on standard input when a newline is typed. -After either of these actions, the output point is advanced. -This is different from the working of a regular terminal, -permitting cut-and-paste editing of an input line until the newline is typed. -Arbitrary editing may be done to any text in the window. -The implementation of -</span><span style="font-size: 10pt"><tt>win</tt></span><span style="font-size: 10pt">, -using the -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt">, -</span><span style="font-size: 10pt"><tt>addr</tt></span><span style="font-size: 10pt">, -and -</span><span style="font-size: 10pt"><tt>data</tt></span><span style="font-size: 10pt"> -files, is straightforward. -</span><span style="font-size: 10pt"><tt>Win</tt></span><span style="font-size: 10pt"> -needs no code for handling the keyboard and mouse; it just monitors the -contents of the window. Nonetheless, it allows Acme’s full editing to be -applied to shell commands. -The division of labor between -</span><span style="font-size: 10pt"><tt>win</tt></span><span style="font-size: 10pt"> -and -</span><span style="font-size: 10pt"><tt>Acme</tt></span><span style="font-size: 10pt"> -contrasted with -</span><span style="font-size: 10pt"><tt>xterm</tt></span><span style="font-size: 10pt"> -and the X server demonstrates how much work Acme handles automatically. -</span><span style="font-size: 10pt"><tt>Win</tt></span><span style="font-size: 10pt"> -is implemented by a single source file 560 lines long and has no graphics code. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"></span><span style="font-size: 10pt"><tt>Win</tt></span><span style="font-size: 10pt"> -uses the middle and right buttons to connect itself in a consistent way -with the rest of Acme. -The middle button still executes commands, but in a style more suited -to typescripts. Text selected with the middle button is treated as if -it had been typed after the output point, much as a similar feature in -</span><span style="font-size: 10pt"><tt>xterm</tt></span><span style="font-size: 10pt"> -or -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt">, -and therefore causes it to be ‘executed’ by the application running in the window. -Right button actions are reflected back to Acme but refer to the appropriate -files because -</span><span style="font-size: 10pt"><tt>win</tt></span><span style="font-size: 10pt"> -places the name of the current directory in the tag of the window. -If the shell is running, a simple shell function replacing the -</span><span style="font-size: 10pt"><tt>cd</tt></span><span style="font-size: 10pt"> -command can maintain the tag as the shell navigates the file system. -This means, for example, that a right button click on a file mentioned in an -</span><span style="font-size: 10pt"><tt>ls</tt></span><span style="font-size: 10pt"> -listing opens the file within Acme. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Another Acme-specific program is a mail reader that begins by presenting, -in a window, a listing of the messages in the user’s mailbox, one per line. -Here the middle and right button actions are modified to refer to -mail commands -and messages, but the change feels natural. -Clicking the right button on a line creates a new window and displays the -message there, or, if it’s already displayed, moves the mouse to that window. -The metaphor is that the mailbox is a directory whose constituent files are messages. -The mail program also places some relevant commands in the tag lines of -the windows; for example, executing the word -</span><span style="font-size: 10pt"><tt>Reply</tt></span><span style="font-size: 10pt"> -in a message’s tag creates a new window -in which to compose a message to the sender of the original; -</span><span style="font-size: 10pt"><tt>Post</tt></span><span style="font-size: 10pt"> -then dispatches it. -In such windows, the addressee is just a list of names -on the first line of the body, which may be edited to add or change recipients. -The program also monitors the mailbox, updating the ‘directory’ as new messages -arrive. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The mail program is as simple as it sounds; all the work of interaction, -editing, and management of the display is done by Acme. -The only -difficult sections of the 1200 -lines of code concern honoring the external protocols for managing -the mailbox and connecting to -</span><span style="font-size: 10pt"><tt>sendmail</tt></span><span style="font-size: 10pt">. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">One of the things Acme does not provide directly is a facility like -Sam’s command language to enable actions such as global substitution; -within Acme, all editing is done manually. -It is easy, though, to write external programs for such tasks. -In this, Acme comes closer to the original intent of Oberon: -a directory, -</span><span style="font-size: 10pt"><tt>/acme/edit</tt></span><span style="font-size: 10pt">, -contains a set of tools for repetitive editing and a template -or ‘guide’ file that gives examples -of its use. -Acme’s editing guide, -</span><span style="font-size: 10pt"><tt>/acme/edit/guide</tt></span><span style="font-size: 10pt">, -looks like this: -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>e file | x ’/regexp/’ | c ’replacement’</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>e file:’0,$’ | x ’/.*word.*\n/’ | p -n</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>e file | pipe command args ...</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The syntax is reminiscent of Sam’s command language, but here the individual -one-letter commands are all stand-alone programs connected by pipes. -Passed along the pipes are addresses, analogous to structural expressions -in Sam terminology. -The -</span><span style="font-size: 10pt"><tt>e</tt></span><span style="font-size: 10pt"> -command, unlike that of Sam, starts the process by generating the address -(default dot, the highlighted selection) in the named files. -The other commands are as in Sam: -</span><span style="font-size: 10pt"><tt>p</tt></span><span style="font-size: 10pt"> -prints the addressed text on standard output (the -</span><span style="font-size: 10pt"><tt>-n</tt></span><span style="font-size: 10pt"> -option is analogous to that of -</span><span style="font-size: 10pt"><tt>grep</tt></span><span style="font-size: 10pt">, -useful in combination with the right mouse button); -</span><span style="font-size: 10pt"><tt>x</tt></span><span style="font-size: 10pt"> -matches a regular expression to the addressed (incoming) text, -subdividing the text; -</span><span style="font-size: 10pt"><tt>c</tt></span><span style="font-size: 10pt"> -replaces the text; and so on. Thus, global substitution throughout a file, -which would be expressed in Sam as -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>0,$ x/regexp/ c/replacement/</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">in Acme’s editor becomes -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>e ’file:0,$’ | x ’/regexp/’ | c ’replacement’</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">To use the Acme editing commands, open -</span><span style="font-size: 10pt"><tt>/acme/edit/guide</tt></span><span style="font-size: 10pt">, -use the mouse and keyboard to edit one of the commands to the right form, -and execute it with the middle button. -Acme’s context rules find the appropriate binaries in -</span><span style="font-size: 10pt"><tt>/acme/edit</tt></span><span style="font-size: 10pt"> -rather than -</span><span style="font-size: 10pt"><tt>/bin</tt></span><span style="font-size: 10pt">; -the effect is to turn -</span><span style="font-size: 10pt"><tt>/acme/edit</tt></span><span style="font-size: 10pt"> -into a toolbox containing tools and instructions (the guide file) for their use. -In fact, the source for these tools is also there, in the directory -</span><span style="font-size: 10pt"><tt>/acme/edit/src</tt></span><span style="font-size: 10pt">. -This setup allows some control of the file name space for binary programs; -not only does it group related programs, it permits the use of common -names for uncommon jobs. For example, the single-letter names would -be unwise in a directory in everyone’s search path; here they are only -visible when running editing commands. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">In Oberon, -such a collection would be called a -</span><span style="font-size: 10pt"><i>tool</i></span><span style="font-size: 10pt"> -and would consist -of a set of entry points in a module and a menu-like piece of text containing -representative commands that may be edited to suit and executed. -There is, in fact, a tool called -</span><span style="font-size: 10pt"><tt>Edit</tt></span><span style="font-size: 10pt"> -in Oberon. -To provide related functionality, -Acme exploits the directory and file structure of the underlying -system, rather than the module structure of the language; -this fits well with Plan 9’s -file-oriented philosophy. -Such tools are central to the working of Oberon but they are -less used in Acme, at least so far. -The main reason is probably that Acme’s program interface permits -an external program to remain executing in the background, providing -its own commands as needed (for example, the -</span><span style="font-size: 10pt"><tt>Reply</tt></span><span style="font-size: 10pt"> -command in the mail program); Oberon uses tools to -implement such services because its must invoke -a fresh program for each command. -Also, -Acme’s better integration allows more -basic functions to be handled internally; the right mouse button -covers a lot of the basic utility of the editing tools in Oberon. -Nonetheless, as more applications are written for Acme, -many are sure to take this Oberon tool-like form. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Comparison with other systems -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme’s immediate ancestor is Help [Pike92], an experimental system written -a few years ago as a first try at exploring some of Oberon’s ideas -in an existing operating system. -Besides much better engineering, Acme’s advances over Help -include the actions of the right button (Help had nothing comparable), -the ability to connect long-running programs to the user interface -(Help had no analog of the -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt"> -file), -and the small but important change to split command output into -windows labeled with the directory in which the commands run. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Most of Acme’s style, however, derives from the user interface and window -system of Oberon [Wirt89, Reis91]. -Oberon includes a programming language and operating system, -which Acme instead borrows from an existing system, Plan 9. -When I first saw Oberon, in 1988, I was struck by the -simplicity of its user interface, particularly its lack of menus -and its elegant use of multiple mouse buttons. -The system seemed restrictive, though—single process, -single language, no networking, event-driven programming—and -failed to follow through on some of its own ideas. -For example, the middle mouse button had to be pointed accurately and -the right button was essentially unused. -Acme does follow through: -to the basic idea planted by Oberon, it adds -the ability to run on different operating systems and hardware, -connection to existing applications including -interactive ones such as shells and debuggers, -support for multiple processes, -the right mouse button’s features, -the default actions and context-dependent properties -of execution and searching, -and a host of little touches such as moving the mouse cursor that make the system -more pleasant. -At the moment, though, Oberon does have one distinct advantage: it incorporates -graphical programs well into its model, an issue Acme has not yet faced. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme shares with the Macintosh a desire to use the mouse well and it is -worth comparing the results. -The mouse on the Macintosh has a single button, so menus are essential -and the mouse must frequently move a long way -to reach the appropriate function. -An indication that this style has trouble is that applications provide -keyboard sequences to invoke menu selections and users often prefer them. -A deeper comparison is that the Macintosh uses pictures where Acme uses text. -In contrast to pictures, text can be edited quickly, created on demand, -and fine-tuned to the job at hand; consider adding an option to a command. -It is also self-referential; Acme doesn’t need menus because any text can be -in effect a menu item. -The result is that, although a Macintosh screen is certainly prettier and probably -more attractive, especially to beginners, an Acme screen is more dynamic -and expressive, at least for programmers and experienced users. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">For its role in the overall system, -Acme most resembles EMACS [Stal93]. -It is tricky to compare Acme to EMACS, though, because there are -many versions of EMACS and, since it is fully programmable, EMACS -can in principle do anything Acme does. -Also, Acme is much younger and therefore has not -had the time to acquire as many features. -The issue therefore is less what the systems can be programmed to do than -how they are used. -The EMACS versions that come closest to Acme’s style are those that -have been extended to provide a programming environment, usually -for a language such as LISP [Alle92, Lucid92]. -For richness of the existing interface, these EMACS versions are certainly superior to Acme. -On the other hand, Acme’s interface works equally well already for a variety -of languages; for example, one of its most enthusiastic users works almost -exclusively in Standard ML, a language nothing like C. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Where Acme excels is in the smoothness of its interface. -Until recently, EMACS did not support the mouse especially well, -and even with the latest version providing features such as ‘extents’ -that can be programmed to behave much like Acme commands, -many users don’t bother to upgrade. -Moreover, in the versions that provide extents, -most EMACS packages don’t take advantage of them. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The most important distinction is just that -EMACS is fundamentally keyboard-based, while -Acme is mouse-based. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">People who try Acme find it hard to go back to their previous environment. -Acme automates so much that to return to a traditional interface -is to draw attention to the extra work it requires. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Concurrency in the implementation -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme is about 8,000 lines of code in Alef, a concurrent object-oriented language syntactically similar to C [Alef]. -Acme’s structure is a set of communicating -processes in a single address space. -One subset of the processes drives the display and user interface, -maintaining the windows; other processes forward mouse and keyboard -activity and implement the file server interface for external programs. -The language and design worked out well; -as explained elsewhere [Pike89, Gans93, Reppy93], -user interfaces built with concurrent systems -can avoid the clumsy -top-level event loop typical of traditional interactive systems. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">An example of the benefits of the multi-process style -is the management of the state of open -files held by clients of the file system interface. -The problem is that some I/O requests, -such as reading the -</span><span style="font-size: 10pt"><tt>event</tt></span><span style="font-size: 10pt"> -file, may block if no data is available, and the server must -maintain the state of (possibly many) requests until data appears. -For example, -in -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt">, -a single-process window system written in C, pending requests were queued in -a data structure associated with each window. -After activity in the window that might complete pending I/O, -the data structure was scanned for requests that could now finish. -This structure did not fit well with the rest of the program and, worse, -required meticulous effort -to guarantee correct behavior under all conditions -(consider raw mode, reads of partial lines, deleting a window, -multibyte characters, etc.). -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme instead creates a new dedicated process -for each I/O request. -This process coordinates with the rest of the system -using Alef’s synchronous communication; -its state implicitly encodes the state of -the I/O request and obviates the need for queuing. -The passage of the request through Acme proceeds as follows. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme contains a file server process, F, that executes a -</span><span style="font-size: 10pt"><tt>read</tt></span><span style="font-size: 10pt"> -system call to receive a Plan 9 file protocol (9P) message from the client [AT&T92]. -The client blocks until Acme answers the request. -F communicates with an allocation process, M, -to acquire an object of type -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt"> -(‘executing fid’; fid is a 9P term) -to hold the request. -M sits in a loop (reproduced in Figure 2) waiting for either a request for -a new -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt"> -or notification that an existing one has finished its task. -When an -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt"> -is created, an associated process, X, -is also made. -M queues idle -</span><span style="font-size: 10pt"><tt>Xfids</tt></span><span style="font-size: 10pt">, -allocating new ones only when the list is empty. -Thus, there is always a pool of -</span><span style="font-size: 10pt"><tt>Xfids</tt></span><span style="font-size: 10pt">, -some executing, some idle. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt"> -object contains a channel, -</span><span style="font-size: 10pt"><tt>Xfid.c</tt></span><span style="font-size: 10pt">, -for communication with its process; -the unpacked message; and some associated functions, -mostly corresponding to 9P messages such as -</span><span style="font-size: 10pt"><tt>Xfid.write</tt></span><span style="font-size: 10pt"> -to handle a 9P write request. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The file server process F parses the message to see its nature—open, -close, read, write, etc. Many messages, such as directory -lookups, can be handled immediately; these are responded to directly -and efficiently -by F without invoking the -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt">, -which is therefore maintained until the next message. -When a message, such as a write to the display, requires the attention -of the main display process and interlocked access to its data structures, -F enables X -by sending a function pointer on -</span><span style="font-size: 10pt"><tt>Xfid.c</tt></span><span style="font-size: 10pt">. -For example, if the message is a write, F executes -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>x->c <-= Xfid.write;</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">which sends -the address of -</span><span style="font-size: 10pt"><tt>Xfid.write</tt></span><span style="font-size: 10pt"> -on -</span><span style="font-size: 10pt"><tt>Xfid.c</tt></span><span style="font-size: 10pt">, -waking up X. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">The -</span><span style="font-size: 10pt"><tt>Xfid</tt></span><span style="font-size: 10pt"> -process, X, executes a simple loop: -</span></p><p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>void</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>Xfid.ctl(Xfid *x)</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>{</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt> for(;;){</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt> (*<-x->c)(x); /* receive and execute message */</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt> bflush(); /* synchronize bitmap display */</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt> cxfidfree <-= x; /* return to free list */</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt> }</tt></span></p> -<p style="line-height: 1.1em; margin-left: 1.28in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 9pt"><tt>}</tt></span></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="margin-top: 0; margin-bottom: 0.08in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Thus X -will wake up with the address of a function to call (here -</span><span style="font-size: 10pt"><tt>Xfid.write</tt></span><span style="font-size: 10pt">) -and execute it; once that completes, it returns itself to the pool of -free processes by sending its address back to the allocator. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Although this sequence may seem complicated, it is just a few lines -of code and is in fact far simpler -than the management of the I/O queues in -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt">. -The hard work of synchronization is done by the Alef run time system. -Moreover, the code worked the first time, which cannot be said for the code in -</span><span style="font-size: 10pt"><tt>8½</tt></span><span style="font-size: 10pt">. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Undo -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme provides a general undo facility like that of Sam, permitting -textual changes to be unwound arbitrarily. -The implementation is superior to Sam’s, though, -with much higher performance and the ability to ‘redo’ changes. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Sam uses -a multi-pass algorithm that builds -a transcript of changes to be made simultaneously -and then executes them atomically. -This was thought necessary because the elements of a repetitive -command such as a global substitution should all be applied to the same -initial file and implemented simultaneously; forming the complete -transcript before executing any of the changes avoids the -cumbersome management of addresses in a changing file. -Acme, however, doesn’t have this problem; global substitution -is controlled externally and may be made incrementally by exploiting -an observation: if the changes are sorted in address order and -executed in reverse, changes will not invalidate the addresses of -pending changes. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme therefore avoids the initial transcript. Instead, changes are applied -directly to the file, with an undo transcript recorded in a separate list. -For example, when text is added to a window, it is added directly and a record -of what to delete to restore the state is appended to the undo list. -Each undo action and the file are marked with a sequence number; -actions with the same sequence number are considered a unit -to be undone together. -The invariant state of the structure -is that the last action in the undo list applies to the current state of the file, -even if that action is one of a related set from, for example, a global substitute. -(In Sam, a related set of actions needed to be undone simultaneously.) -To undo an action, pop the last item on the undo list, apply it to the file, -revert it, and append it to a second, redo list. -To redo an action, do the identical operation with the lists interchanged. -The expensive operations occur -only when actually undoing; in normal editing the overhead is minor. -For example, Acme reads files about seven times faster than Sam, partly -because of this improvement and partly because of a cleaner implementation. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme uses a temporary file to hold the text, keeping in memory only the -visible portion, and therefore can edit large files comfortably -even on small-memory machines such as laptops. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Future -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme is still under development. -Some things are simply missing. -For example, Acme should support non-textual graphics, but this is being -deferred until it can be done using a new graphics model being developed -for Plan 9. Also, it is undecided how Acme’s style of interaction should best be -extended to graphical applications. -On a smaller scale, although the system feels smooth and comfortable, -work continues to tune the heuristics and -try new ideas for the user interface. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">There need to be more programs that use Acme. Browsers for -Usenet and AP News articles, the Oxford English Dictionary, and other -such text sources exist, but more imaginative applications will -be necessary to prove that Acme’s approach is viable. -One that has recently been started is an interface to the debugger Acid [Wint94], -although it is still -unclear what form it will ultimately take. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme shows that it is possible to make a user interface a stand-alone component -of an interactive environment. By absorbing more of the interactive -functionality than a simple window system, Acme off-loads much of the -computation from its applications, which helps keep them small and -consistent in their interface. Acme can afford to dedicate -considerable effort to making that interface as good as possible; the result -will benefit the entire system. -</span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Acme is complete and useful enough to attract users. -Its comfortable user interface, -the ease with which it handles multiple tasks and -programs in multiple directories, -and its high level of integration -make it addictive. -Perhaps most telling, -Acme shows that typescripts may not be the most -productive interface to a time-sharing system. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>Acknowledgements -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.35in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Howard Trickey, Acme’s first user, suffered buggy versions gracefully and made -many helpful suggestions. Chris Fraser provided the necessary insight for the Acme editing -commands. -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"><b>References -</b></span></p><p style="margin-top: 0; margin-bottom: 0.05in"></p> -<p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Alef] P. Winterbottom, -‘‘Alef Language Reference Manual’’, -</span><span style="font-size: 10pt"><i>Plan 9 Programmer’s Manual, -</i></span><span style="font-size: 10pt">AT&T Bell Laboratories, -Murray Hill, NJ, -1992; -revised in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Alle92] -</span><span style="font-size: 10pt"><i>Allegro Common Lisp user Guide, Vol 2, -</i></span><span style="font-size: 10pt">Chapter 14, "The Emacs-Lisp Interface". -March 1992. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[AT&T92] Plan 9 Programmer’s manual, Murray Hill, New Jersey, 1992. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Far89] Far too many people, XTERM(1), Massachusetts Institute of Technology, 1989. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Gans93] Emden R. Gansner and John H. Reppy, ‘‘A Multi-threaded Higher-order User Interface Toolkit’’, in -</span><span style="font-size: 10pt"><i>Software Trends, Volume 1, -User Interface Software, -</i></span><span style="font-size: 10pt">Bass and Dewan (Eds.), -John Wiley & Sons 1993, -pp. 61-80. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Lucid92] Richard Stallman and Lucid, Inc., -</span><span style="font-size: 10pt"><i>Lucid GNU EMACS Manual, -</i></span><span style="font-size: 10pt">March 1992. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike87] Rob Pike, ‘‘The Text Editor </span><span style="font-size: 10pt"><tt>sam</tt></span><span style="font-size: 10pt">’’, Softw. - Pract. and Exp., Nov 1987, Vol 17 #11, pp. 813-845; reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike88] Rob Pike, ‘‘Window Systems Should Be Transparent’’, Comp. Sys., Summer 1988, Vol 1 #3, pp. 279-296. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike89] Rob Pike, ‘‘A Concurrent Window System’’, Comp. Sys., Spring 1989, Vol 2 #2, pp. 133-153. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[PPTTW93] Rob Pike, Dave Presotto, Ken Thompson, Howard Trickey, and Phil Winterbottom, ‘‘The Use of Name Spaces in Plan 9’’, -Op. Sys. Rev., Vol. 27, No. 2, April 1993, pp. 72-76, -reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike91] Rob Pike, ‘‘8½, the Plan 9 Window System’’, USENIX Summer Conf. Proc., Nashville, June, 1991, pp. 257-265, -reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike92] Rob Pike, ‘‘A Minimalist Global User Interface’’, Graphics Interface ’92 Proc., Vancouver, 1992, pp. 282-293. An earlier version appeared under the same title in USENIX Summer Conf. Proc., Nashville, June, 1991, pp. 267-279. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pike93] Rob Pike and Ken Thompson, ‘‘Hello World or Καλημέρα κόσμε or -</span><span style="font-size: 10pt">こんにちは 世界</span><span style="font-size: 10pt">’’, USENIX Winter Conf. Proc., San Diego, 1993, pp. 43-50, -reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Pres93] Dave Presotto and Phil Winterbottom, ‘‘The Organization of Networks in Plan 9’’, Proc. Usenix Winter 1993, pp. 271-287, San Diego, CA, -reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Reis91] Martin Reiser, </span><span style="font-size: 10pt"><i>The Oberon System,</i></span><span style="font-size: 10pt"> Addison Wesley, New York, 1991. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Reppy93] John H. Reppy, -‘‘CML: A higher-order concurrent language’’, Proc. SIGPLAN’91 Conf. on Programming, Lang. Design and Impl., June, 1991, pp. 293-305. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Sche86] Robert W. Scheifler and Jim Gettys, -‘‘The X Window System’’, -ACM Trans. on Graph., Vol 5 #2, pp. 79-109. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Stal93] Richard Stallman, -</span><span style="font-size: 10pt"><i>Gnu Emacs Manual, 9th edition, Emacs version 19.19, -</i></span><span style="font-size: 10pt">MIT. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Swei86] Daniel Sweinhart, Polle Zellweger, Richard Beach, and Robert Hagmann, -‘‘A Structural View of the Cedar Programming Environment’’, -ACM Trans. Prog. Lang. and Sys., Vol. 8, No. 4, pp. 419-490, Oct. 1986. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Wint94], Philip Winterbottom, ‘‘Acid: A Debugger based on a Language’’, USENIX Winter Conf. Proc., San Francisco, CA, 1993, -reprinted in this volume. -</span></p><p style="line-height: 1.2em; margin-left: 1.00in; text-indent: 0.00in; margin-right: 1.00in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">[Wirt89] N. Wirth and J. Gutknecht, ‘‘The Oberon System’’, Softw. - Prac. and Exp., Sep 1989, Vol 19 #9, pp 857-894. -</span></p><p style="margin-top: 0; margin-bottom: 0.50in"></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="line-height: 1.2em; margin-left: 1.50in; text-indent: 0.35in; margin-right: 1.50in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt"></span><span style="font-size: 10pt"><b>Notes</b></span><span style="font-size: 10pt"> -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -<p style="line-height: 1.2em; margin-left: 1.50in; text-indent: 0.00in; margin-right: 1.50in; margin-top: 0; margin-bottom: 0; text-align: justify;"> -<span style="font-size: 10pt">Originally appeared in -</span><span style="font-size: 10pt"><i>Proc. of the Winter 1994 USENIX Conf., -</i></span><span style="font-size: 10pt">pp. 223-234, -San Francisco, CA -</span></p><p style="margin-top: 0; margin-bottom: 0.17in"></p> -<p style="margin-top: 0; margin-bottom: 0.17in"></p> - -</body> -</html> - |