Again it is time to fire up the machine and check your work. The following program checks the low resolution graphics. It can be run in either Applesoft or Integer Basic.

• 10 OR : C=-1
• 20 C=C+1 : COLOR=C
• 30 VLIN 0,39 AT 2*C
• 40 IF C<16 THEN GOTO 20 : END

The following program was written by Andre Pilon and checks the high resolution graphics. It must be run in Applesoft Basic.

• 5 HGR
• 10 C=INT (RND (1) * 7 )
• 15 HCOLOR=C
• 17 SPEED = RND (1) * 250
• 20 LET X = INT ( RND ( 1 ) * 279 )
• 30 LET Z = INT ( RND ( 1 ) * 160 )
• 40 HPLOT 139,80 TO X,Z
• 50 GOTO 10

If either of these programs runs, but you get only shades of grey on a color monitor or TV set the likly problem is that the crystal frequency is off. If you have a frequency counter, measure B14-3 and adjust the crystal trimmer capacitor for 3.579545 MHz. If you do not have a counter adjust the trimmer for the center of the range where you get a color display on the monitor. If your monitor is black and white and these programs produce shades of grey then your graphics circuits are probably OK, however the frequency might still be off.