GASS Operations

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GASS TERMINAL CONTROL

The GASS system has traditionally used terminals compatible with the
Televideo 910, 912 & 920 series. These include the Lear-Siegler ADM-3A
and ADM-5, the Wyse WY-30 and the Qume QVT-101. These terminals are
generally the cheapest available and have all proven to have excellent
service life.

When GASS was implemented in the IBM-PC and compatibles, it became
necessary to provide the console driver of the PC with a common subset
of the control sequences that were available on the terminals in use, so
that software written for the terminals would act the same on the
monitor of the PC console.

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CAUTION: The console screen on the PC has 25 lines, but most terminals
have only 24 lines. If your programs need to run on both, DO NOT USE THE
25th LINE! If you try to use this extra line, the terminal WILL SCROLL,
thus destroying your carefully formatted screens. Take it from someone
who has made this mistake; fixing it takes a lot of time.
------------------------------------------------------------------------

The console control sequences available are:

CHARACTERS         ACTION

^G                 audible bell or beep

^H                 backspace

^J                 line feed

^K                 upline

^M                 carriage return (echoed with line feed added)

^P                 passes next char through without interpretation

^Z                 clear screen & home cursor

ESC Q              insert char at cursor (last char on line is lost)

ESC W              delete char at cursor (last char on line is blank)

ESC E              insert a line at cursor position, scrolling screen
                   down

ESC R              delete line at cursor position, scrolling screen up

ESC T              erase line from cursor to end of line

ESC Y              erase screen from cursor position to end of screen

ESC = Y X          position cursor at Y & X coordinates where Y & X are
                   ASCII characters and the space char represents a
                   position value of zero, i.e. the positions are offset
                   by a decimal value of 32, and the range of Y values
                   is 0-24 and the range of X values is 0-79. Charts are
                   available in most terminal manuals to assist in
                   determining the proper cursor coordinates.

Note that if the comment of a field is of the form Y:yyX:xx, where yy
represents the screen row and xx represents the screen column, then the
cursor is positioned accordingly when the comment is viewed by an Op. 0,
55, etc. This is done by translating the values contained in the comment
to the ESC= sequence as above. This function also transmits blanks equal
to the width of the field and the repositions the cursor at the location
specified, and is used for fill-in-the-blanks type screen entry.

Careful planning of your report formats will allow you to create
professional-looking input routines for your GASS applications. You may
also use the simple TTY-like nature of GASS and allow the screen to
scroll from top to bottom with less planning and simpler, more nearly
self-documenting report formats like those contained in the examples in
the manual.

Note also that sequences specific to your particular terminal that are
not listed here may be used on those terminals, but will not work on the
PC console. We will, however, consider implementing other control
sequences, given sufficient need or remuneration. Call us to discuss
your specific problems or needs.
Gass Index