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Preface - Adobe

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2.4<br />

21<br />

Using the PostScript Language<br />

TABLE 2.1 Control characters for the interactive executive<br />

CHARACTER FUNCTION<br />

Backspace (BS) Backs up and erases one character.<br />

Delete (DEL) Same as backspace.<br />

Control-U Erases the current line.<br />

Control-R Redisplays the current line.<br />

Control-C Aborts the entire statement and starts over. Control-C can also<br />

abort a statement that is executing and force the executive to revert<br />

to a PS> prompt.<br />

There are several important things to understand about the interactive executive:<br />

• It is intended solely for direct interaction with the user; an application that is<br />

generating PostScript programs should never invoke executive. In general, a<br />

PostScript program will behave differently when sent through the interactive<br />

executive than when executed directly by the PostScript interpreter. For example,<br />

the executive produces extraneous output such as echoes of the input characters<br />

and PS> prompts. Furthermore, a program that explicitly reads data<br />

embedded in the program file will malfunction if invoked via the executive,<br />

since the executive itself is interpreting the file.<br />

• The user amenities are intentionally minimal. The executive is not a full-scale<br />

programming environment; it lacks a text editor and other tools required for<br />

program development and it does not keep a record of your interactive session.<br />

The executive is useful mainly for experimentation and debugging.<br />

• The executive operator is not necessarily available in all PostScript interpreters.<br />

Its behavior may vary among different products.

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