=> R0 = 160 (&A0)
R1 = VDU variable number
<= R0 preserved
R1 = value of variable
R2 = value of next variable (entry R1 + 1)
This call is provided for compatibility with the BBC/Master 128, and reads various VDU variables. Note that it does not use the same numbers for variables as OS_ReadVDUVariables, and that that SWI can read many more variables.
See PRM 1, page 652
OS_Byte 160 VDU variable numbers
Number Value
0 LSB of graphics window left column (ic)
1 MSB of graphics window left column (ic)
2 LSB of graphics window bottom row (ic)
3 MSB of graphics window bottom row (ic)
4 LSB of graphics window right column (ic)
5 MSB of graphics window right column (ic)
6 LSB of graphics window top row (ic)
7 MSB of graphics window top row (ic)
8 text window left column
9 text window bottom row
10 text window right column
11 text window top row
12 LSB of graphics origin x coordinate (ec)
13 MSB of graphics origin x coordinate (ec)
14 LSB of graphics origin y coordinate (ec)
15 MSB of graphics origin y coordinate (ec)
ic (internal coordinates)
The origin is always the bottom left of the screen. One unit is one pixel wide and one pixel high.
ec (external coordinates)
A pixel is (1 << XEigFactor) units wide and (1 << YEigFactor) units high, where XEigFactor and YEigFactor are VDU variables.
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