Atari XL

38
The Atari XL Handbook
which they were typed in. Again, a R ...
loop is used.
The lines from 210 to 280 sort the numbers in
the array SORT(IO) into ascending order. A
FOR ... NEXT loop compares each element of
the array SORT with the next, and swaps them
over if they are in the wrong order. A variable,
COUNT, keeps track of the number of these
swaps and, if at the end of the loop this isn't
zero, the loop is repeated.
Lines 310 to 330 complete the program by
PRINTing the two sets of numbers.
PAUSES
To make a pause during the running of a program,
we can use a FOR ... NEXT loop which does
nothing at all except count its way through the
steps. The following program is an example:
10 FOR T = 0 TO 5000
20 NEXT T
30 PRINT "ABOUT 10 SECONDS"
Another way to make a pause is to use the Atari's
built in timer: The three storage locations 18, 19
and 20 are incremented about 5 times a second, so
for a 10 second wait, try:
10 POKE 19,0:POKE 20,0
20 IF PEEK(19) < 2 THEN 20
30 PRINT" [BELL] "
(The BELL character is obtained by pressing ESC
then holding down CONTROL and pressing 2.)