Radio Shack TRS-80 Model II Reference Manual page 201

Technical Information
VDGRAF
Video Graphics (function code 10)
This function displays a buffer of characters, starting at a specified row and
column. It is a Graphics Mode routine (the cursor "wraps" the Display).
Displayable Characters
This routine lets you display the 32 graphics characters (and their reverse
images). The codes are numbered from 0 through
X'lF',
and are pictured in
the Operator's Manual. Codes
X'20'
through
X'7F'
are displayed as standard
ASCII
characters.
In addition, several special control codes are available:
HEX
CODE FUNCTION
F9
Sets Normal (white on black) mode. Cursor does not advance.
Mode reverts to previous state after completion of
VDGRAF
call.
FA Sets Reverse (black on white) mode. Cursor does not advance.
Mode reverts to previous state after completion of
VDGRAF
call.
FS Homes cursor (RowO, Column 0).
FC Moves cursor back one space. Col. = Col-1. When column equals 0,
cursor wraps to Col. 79 on the preceding row.
FD
Moves cursor forward one space. Col.
=
Col.
+
1. When column
equals 79, cursor wraps to Col. 0 on the next row down.
FE Moves cursor up one row. Row = Row-1. "Wraps" to Row 23 when
Row=O.
FF
Moves cursor down one row. Row
=
Row
+
1. "Wraps" up to Row 0
when Row
=
23.
Table 4.8. Special Graphics Control Codes
At exit, the cursor is always set to the Graphics position immediately after the
last character displayed. If the Buffer length was zero, the cursor is set to
position specified in
BC
registers.
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