WHILE

Repeatedly execute a statement

WSupported on Windows

USupported on Unix

VSupported on OpenVMS

NSupported in Synergy .NET

WHILE condition [DO] statement

Arguments

condition

A conditional expression that is evaluated before each repetition of the specified statement.

statement

A single or compound statement to be executed repeatedly.

Discussion

The WHILE statement executes a statement repeatedly as long as a specified condition is true. Statement is executed while condition is true. When the condition becomes false, control transfers to the logical statement after the WHILE.

Statement can be on the next logical line from WHILE condition. If DO is present, it must be on the same logical line as WHILE.

Statement is not executed if condition is false at the initial iteration.

Examples

The following example performs password validation.

.define TTCHN           ,1
record
    password            ,a5
proc
    open(TTCHN, o, "tt:")
    xcall flags(50000, 1)                       ;Turn off input echo
    while (password .ne. "DEMO ") do
      begin
        display(TTCHN, "Enter password:  ")
        reads(TTCHN, password, exit)
        if (password .ne. "DEMO")
          begin
            writes(TTCHN, "Invalid password")
            sleep 1
          end
      end
    display(TTCHN, $scr_clr(screen), "XYZ Payroll System")
    xcall process               ;Start the package
exit,
    stop
end