Commodore Plus 4 - Color and reverse printing

42 The BASIC Language
10 F0RY = 1T0 3
SO FOR Z = 6 TO 1 STEP -2
30 PRINT "Z =";Z;
40 PRINT "Y ="; Y
50 NEXT Z: NEXT Y This line could also read NEXT Z,Y.
RUN
Z = 6 Y = 1 While Y, which is part of the outer loop, executes
Z = 4 Y = 1 once, Z5 from the inner loop, executes all three times.
Z = 2 Y = 1 When Y makes its second execution, Z repeats
Z = 6 Y = 2 another full set, and so on.
Z=4 Y=2
Z=2 Y=2
Z=6 Y=3
Z=4 Y=3
Z=2 Y=3
FRE Abbr. fR
FRE (number)
Examines the number of available bytes of RAM. Use PRINT FRE(O) to
display the amount of memory available. The FRE function uses a dummy
argument, which means that the number in parentheses is meaningless. You have
to include the parameter anyway; just type FRE(O).
GET Abbr. gE
GET input list
Like INPUT, GET accepts input from the keyboard during program execu
tion. GET, however, accepts only a single character at a time as data entry. In
addition, GET does not wait for input, but returns a null (empty) string if no key
is pressed. This allows you to check repeatedly for keyboard entry while other
operations continue. To force the computer to wait for input, use the GETKEY
command.
Parameter: variable(s)
The variable is nearly always a string variable. It stands for the key to be typed
in response to the GET command. Use of a numeric variable allows only the 0
through 9 keys to be entered. Any other key causes a type mismatch error, which
aborts the program unless TRAPped.
Example: 10 PRINT "PRESS A KEY TO STOP ME" Prints message to the screen.
SO GET A$:IP A$="" THEN 10 If no key is pressed, then go
to 10.
30 PRINT "WHAT A RELIEF" Program continues normally.