Use the while keyword to conditionally iterate a statement. The syntax of the while statement is:

while expression do statement

statement is executed repeatedly as long as expression evaluates true. The test takes place before the statement is executed. Thus, if expression evaluates false on the first pass, the loop does not execute.

Here is an example of calculating scalar product of two vectors, using the while statement:

s := 0; i := 0;
while i < n do
begin
  s := s + a[i] * b[i];
  i := i + 1;
end;

Probably the easiest way to create an endless loop is to use the statement:

while TRUE do ...;

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