Remote-processing BASIC 52 Uživatelský manuál stáhnout pdf (Strana 52)

RPBASIC-52 PROGRAMMING GUIDE

2-33

DO-UNTIL

Syntax: DO

{program statements}

UNTIL relational expr

Where: relational expr is any logical evaluation such as =, <, >, etc.

Function: Executes a number of program statements a relational expression is true.

Mode: Run

Use: 100 A=0 : DO : A=A+1 : PRINT A : UNTIL A=4 : PRINT "Done"

Cards: All

DESCRIPTION

This statement always executes at least once. DO-UNTIL loops may be nested. This loop may be exited

without meeting relational expr by executing a CLE AR or C LEAR S statem ent.

This statement always executes to UNTIL once. When relational expr is evaluated and if it is false, program

flow branches bac k to DO. If true , program resume s at the next sta teme nt after UN TIL.

When there are no {program statem ents} between DO and UNTIL, and {relational expr} is false, the "loop"

will repeat forever, or until a <ctrl-c> is typed at the console.

DO-UNTIL and DO-WH ILE loops can be nested.

DO-WHILE, FOR-TO-NEXT-STEP

ERROR

BAD SYNTAX When relational expr is omitted

EXAMPLE

The following program stays in a DO-UNTIL loop until a line has changed.

10 ON LINE 0,0,500

20 DO

30 UNTIL C=1

40 PRINT "Line 0 changed. Is now a",line(0)

50 C=0

60 GOTO 20

500 C=1

510 RETURN

>run

Line 0 changed. Is now a 0

Line 0 changed. Is now a 1

Line 0 changed. Is now a 0

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 162 163

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Remote-processing BASIC 52 Uživatelský manuál Strana 52