Radio Shack TRS-80 - Page 42

Operation Manual
Computer Graphics
-----------TRS·BO ® ----------
1 CLEAR l~~
5 SCREEN ~
l~ TILE$(~)=CHR$(&H22)+CHR$(&H~~)
2~ TILE$(l)=CHR$(&HFF)+CHR$(&H~~)
3~ TILE$(2)=CHR$(&H99)+CHR$(&H66)
4~ TILE$(3)=CHR$(&H99)
5~ TILE$(4)=CHR$(&HFF)
6~ TILE$(5)=CHR$(&HF~)+CHR$(&HF~)+CHR$(&H~F)+CHR$(&H~F)
7~ TILE$(6)=CHR$(&H3C)+CHR$(&H3C)+CHR$(&HFF)
8~ TILE$(7)=CHR$(&H~3)+CHR$(&H~C)+CHR$(&H3~)+CHR$(&HC~)
9~ A$=TILE$(~)+TILE$(1)+TILE$(2)+TILE$(3)+TILE$(4)
+TILE$(5)+TILE$(6)+TILE$(7)
l~~ PAINT(3~~,1~~),A$,1
This example paints the screen with a tiling pattern made up
of eight individually defined tile strings (~-7).
'POINT (function)
Returns Pixel Value
The &POINT command lets you read the OFF/ON value of a pixel
from the screen.
Values for &POINT that are off the screen (i.e., PRINT
&POINT (8~~,5~~» return a -1, signifying the pixel is off
the screen.
Example
l~ PSET(3~~,1~~),1
2~ PRINT &POINT(3~~,1~~)
---------ltadl8lhaell---------
-4~-