Commodore VIC-20 User Manual page 360

346
The VIC 20 User Guide
The END statement can provide a program with one or more.
termination points at locations other than the physical end of the program.
END statements can be used to terminate individual programs when more
than one program is in memory at the same time. An END statement at the
physical end of the program is optional. The END statement is used in
program mode only.
Example:
20001 END
FOR-NEXT STEP
All statements between the FOR statement and the NEXT statement
are reexecuted the same number of times.
Format:
FOR nvar
=
start TO end STEP increment
[statements in loop]
NEXT[nvar]
where
nvar
is the index ofthe loop. It holds the current loop count. nvar is often used
by the statements within the loop.
start is a numeric constant, variable, or expression that specifies the beginning
value of the index.
end is a numeric constant, variable, or expression that specifies the ending
value of the index. The loop is completed when the index value is equal
to the end value, or when the index value is incremented or decre-
mented past the end value.
increment
if present, is a numeric constant, variable, or expression that specifies the
amount by which the index variable is to be incremented with each
pass. The step may be incremental (positive) or decremental (negative).
If STEP is omitted, the increment defaults to I.
nvar
may optionally be included in the NEXT statement. A single
NEXT statement is permissible for nested loops that end at the same point.
The NEXT statement then takes the form
NEXT nvar1,nvar
Z •••
The FOR-NEXT loop will always be executed at least once, even ifthe
beginning
nvar
value is beyond the end
nvar
value. If the NEXT statement is
omitted and no subsequent NEXT statements are found, the loop is
executed once.