Atari XL - Page 236

224 The Alar; XL Handbook
7 Put all subroutines 'near the start of the
program. The computer searches through the
whole program for a subroutine each time a
GOSUB command is executed, and
subroutines having low line numbers will be
found and executed more quickly than those
at the end of the program.
8 Programs involving large amounts of
calculation but not requiring the screen
display may be speeded up by turning off the
screen, wi th a line such as :
100 A=PEEK(559):POKE 559,0
The screen can be turned back on to display
the results of the calculations with a
statement:
200 POKE 559,A