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It is possible to place the CAP on the circumference of a circle after
it has been drawn by using the PLOT command, with the circle radius given as
the plot distance. Obviously the same RATIO value must be used for the PLOT
and CIRCLE commands for the result to be correct.
To alter a single pixel at the CAP co-ordinates dependent on the
current PEN mode.
The following is a BASIC program that follows the actions taken by the
CIRCLE command. Execution is slower as the CIRCLE command is a machine code
subroutine and does not involve any of the overheads associated with a BASIC
10 STARTAT X,Y : REM THE MIDDLE OF THE SCREEN
20 FOR A=0 TO 360
40 PLOT A,R : REM RIS THE RADIUS OF THE CIRCLE
50 PENDOWN : DOCAP : PENRET
60 NEXT A
The CAP command has been added to assist the programmer. It reports
the CAP co-ordinates, allowing a programs action to be investigated.
CAP‰ CC,RR reports the co-ordinates on the screen at the specified
CC,RR screen co-ordinates. This action does not effect the cursor address so
that subsequent print statements will act correctly.
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This reports the CAP co-ordinates on a printer allowing a program’s
action to be investigated.
To clear the screen of all graphics and alpha-numeric characters.
GCLR (Graphics Clear)
To clear the screen of graphic characters.
CLEOL (CLear To End Of Line)
To clear the display from the current cursor position to the end of
the current line.
To cause scrolling to affect a number of lines (n) on the video