Commodore PET - GRAPHICS

The subtraction routine looks Iike this:
1070 IF AL)=BL GOTO 1100
789012> =943572 • False statement
Program continues at next line
1080 AL=AL+10'fF
AL=7S9012+1000000
AL=17S9012
1 (19(1 AH=AH-l
AH=123456-1
AH~123455
1100 CL$=STR$(INT(AL-BL»
CL$=STR$(~17S9012-~943572l
CL$=STR$(~S45540l
CL$=!SI4151514101
1101 CL$=MID$(CL$,2,LEN(CLS)-1)
CL$=MID$q~lsI4151514Iol.2.7 -1 l
CL$=MID$(I~ISI4151514Iol.2.6)
CL$-!sI4151514Iol
1102 CL$=LEFT$(ZEROS,F-LEN(CL$»+CL$
CL$=LEFT$(ZERO$.6-6l+CL$
CL$=LEFT$(ZERO$.O)+lsI4151514101
CL$-ISI4151514Iol
1110 CH$=STR$CINTCAH-BH»
CH$=STR$(~123455-~57)
CH$=STR$(~12339S)
CH$=I~1112131319Isl
1111 CH$=MIDSCCHS,2,LENCCH$)-1)
CH$=MID$q~1112131319IsI.2. 7 -1)
CH$=MID$q~1112131319IsI.2.6l
CH$=1112131319Isl
212