1. ZPL II, ZBI 2, Set-Get-Do, Mirror, WML Programming Guide
  2. ZBI Commands
  3. DO Loops
  • ZPL II, ZBI 2, Set-Get-Do, Mirror, WML Programming Guide
DO Loops

DO Loops

Processing of the loop is controlled by a
<WHILE/UNTIL>
 expression located on the
DO
 or
LOOP
 line.
Processing a
WHILE
 statement is the same on either the
DO
 or
LOOP
 lines. The Boolean expression is evaluated and if the statement is true, the
LOOP
 continues at the line after the
DO
 statement. Otherwise, the line after the corresponding
LOOP
 is the next line to be processed.
Processing an
UNTIL
 statement is the same on either the
DO
 or
LOOP
 lines. The Boolean expression is evaluated and if the statement is false, the
LOOP
 continues at the line after the
DO
 statement. Otherwise, the line after the corresponding
LOOP
 is the next to be processed.
If
<WHILE/UNTIL>
 is on the
LOOP
 line, the
BODY
 of the loop is executed before the Boolean expression is evaluated.
If neither the
DO
 or
LOOP
 line has a
<WHILE/UNTIL>
 statement, the loop continues indefinitely.
Some notes about
DO-LOOP
s:
  • can be nested
  • cannot overlap
  • have two formats
Format
DO [<WHILE/UNTIL> <Boolean expression>]
~~BODY~~
LOOP [<WHILE/UNTIL> <Boolean expression>]
Example
This is an example of how to use the
DO-LOOP
 command with the conditional on the DO line:
10 DO WHILE A$="70" 
20 INPUT A$ 
30 LOOP
Example
This is an example of how to use the
DO UNTIL LOOP
 command with conditional on the LOOP line:
10 DO 
20 INPUT A$ 
30 LOOP UNTIL A$="EXIT"
Comments
This is a program command that is preceded by a line number.