While()

In a while loop the content is repeatedly evaluated until the continuation expression evaluates to false. Each time the content is evaluated, the result is appended to the function result. This is similar to the while do ... construct found in many languages.

result := While( continuation , content )

continuation

An expression evaluated just before each iteration which terminates the loop if "FALSE"

content

An expression which is evaluated each iteration with the result being appended to result

result

The concatenation of the results from each iteration

// Transfer the contents of the file input.txt to the file output.txt
a := OpenFile("input.txt");
b := CreateFile("output.txt");
While(Not(EOF(a)),
  Write(b, Read(a))
);
CloseFile(a);
CloseFile(b)