Radio Shack TRS-80 Model II Reference Manual page 200

Model II
TRSDOS
Entry Conditions
B
= ASCII
code for character to be output to the Display; character
codes must be in the range [0,127]
A= 8
Exit Conditions
NZ=
A=
Error
Error Code
VDLINE
Video Line (function code 9)
This routine writes a buffer of data to the Display, starting at the current
cursor position. It is a Scroll Mode routine.
The buffer should contain
ASCII
codes in the range [0,127].
Received control codes, code
X'20' ,
are handled as with
VDCHAR.
Entry Conditions
(HL)
=
Beginning of the buffer containing characters to be set t6 the
Display
B = Number of characters to be sent
C
=
End of line character. This character will be sent to the Display
after the buffer text
A= 9
Exit Conditions
NZ
=
Error
A
=
Error Code
In case of an error:
B
=
Number of characters not displayed, including the one causing
the error
C
=
Character causing the error
Upon return, the cursor is always set to the position following the last
character displayed.
236