Editing Graphics development with vplot (section)

===Control routines===

<syntaxhighlight lang="c">
dev.open()
</syntaxhighlight>
Initialize device-dependent variables (see above)
and emit hardware initialization strings.
This routine is guaranteed to be the first called, and it is only
called once.

<syntaxhighlight lang="c">
dev.reset()
</syntaxhighlight>
Reset the terminal. It is guaranteed that this will be called once
after the first call to dev.open before any other routine is called.
The one exception is in case of certain errors, in which case dev.reset
is never called and instead dev.close(NOTHING) followed by dev.close(DONE)
are the only other calls after the initial dev.open call. (This is the
"No input?" error, which you've probably seen.)

<syntaxhighlight lang="c">
dev.message(command, string)
int command;
char string[];
</syntaxhighlight>
Choose a command from mesgcom.h to position the cursor, set the proper
text mode, and print out a message.  Displaying a message will
require several calls to dev.message, one per command.
The meanings of the various commands are given by comments inside
mesgcom.h.

Generic routines: genmessage.c
Genmessage prints all messages to stderr. It doesn't try to do anything
at all fancy, although it does beep as the best available completely
device-independent way of "highlighting text". It beeps twice because
some devices silently eat single beeps.

<syntaxhighlight lang="c">
dev.erase(command)
int command;
</syntaxhighlight>
Choose an erase mode from erasecom.h, and erase the screen.
The meanings of the various commands are given by comments inside
erasecom.h.

<syntaxhighlight lang="c">
dev.close(status)
int status;
</syntaxhighlight>
Choose a close status from closestat.h, and close the workstation.
The meanings of the various commands are given by comments inside
closestat.h.