These while loops calculate the factorial of 5:

ActionScript 3

var counter: int = 5;
var factorial: int = 1;

while (counter > 1) {
    factorial *= counter;
    counter--;
}

Printf("Factorial = %d", factorial);

Ada

The Wikibook Ada_Programming has a page on the topic of: Control

with Ada.Integer_Text_IO;

procedure Factorial is
    Counter   : Integer := 5;
    Factorial : Integer := 1;
begin
    while Counter > 1 loop
        Factorial := Factorial * Counter;
        Counter   := Counter - 1;
    end loop;

    Ada.Integer_Text_IO.Put (Factorial);
end Factorial;

APL

counter ← 5
factorial ← 1

:While counter > 1
    factorial ×← counter
    counter -← 1
:EndWhile

⎕ ← factorial

or simply

!5

AutoHotkey

counter := 5
factorial := 1

While counter > 1
    factorial *= counter--

MsgBox % factorial

Small Basic

counter = 5    ' Counter = 5
factorial = 1  ' initial value of variable "factorial"

While counter > 1
    factorial = factorial * counter
    counter = counter - 1
EndWhile

TextWindow.WriteLine("Factorial = " + factorial)

Visual Basic

Dim counter As Integer = 5    ' init variable and set value
Dim factorial As Integer = 1  ' initialize factorial variable

Do While counter > 1
    factorial = factorial * counter
    counter = counter - 1
Loop     ' program goes here, until counter = 0

'Debug.Print factorial         ' Console.WriteLine(factorial) in Visual Basic .NET

Bourne (Unix) shell

counter=5
factorial=1
while [ $counter -gt 1 ]; do
    factorial=$((factorial * counter))
    counter=$((counter - 1))
done

echo $factorial

C, C++

int main() {
    int counter = 5;
    int factorial = 1;

    while (counter > 1) {
        factorial *= counter--;
    }

    printf("%d", factorial);
}

ColdFusion Markup Language (CFML)

Script syntax

counter = 5;
factorial = 1;

while (counter > 1) {
    factorial *= counter--;
}

writeOutput(factorial);

Tag syntax

<cfset counter = 5>
<cfset factorial = 1>
<cfloop condition="counter GT 1">
    <cfset factorial *= counter-->
</cfloop>
<cfoutput>#factorial#</cfoutput>

Fortran

program FactorialProg
    integer :: counter = 5
    integer :: factorial = 1

    do while (counter > 1)
        factorial = factorial * counter
        counter = counter - 1
    end do

    print *, factorial
end program FactorialProg

Go

Go has no while statement, but it has the function of a for statement when omitting some elements of the for statement.

counter, factorial := 5, 1

for counter > 1 {
	counter, factorial = counter-1, factorial*counter
}

Java, C#, D

The code for the loop is the same for Java, C# and D:

int counter = 5;
int factorial = 1;

while (counter > 1) {
    factorial *= counter--;
}

JavaScript

let counter = 5;
let factorial = 1;

while (counter > 1)
    factorial *= counter--;

console.log(factorial);

Kotlin

Source:^[3]

var counter = 5
var factorial = 1

while (counter > 1) {
    factorial = factorial * counter
    counter = counter - 1
}

println(factorial)

Lua

counter = 5
factorial = 1

while counter > 1 do
  factorial = factorial * counter
  counter = counter - 1
end

print(factorial)

MATLAB, Octave

counter = 5;
factorial = 1;

while (counter > 0)
    factorial = factorial * counter;      %Multiply
    counter = counter - 1;                %Decrement
end

factorial

Mathematica

Block[{counter=5,factorial=1},  (*localize counter and factorial*)
    While[counter>1,            (*While loop*)
        factorial*=counter;     (*Multiply*)
        counter--;              (*Decrement*)
    ];

    factorial
]

Oberon, Oberon-2, Oberon-07, Component Pascal

MODULE Factorial;
IMPORT Out;
VAR
    Counter, Factorial: INTEGER;
BEGIN
    Counter := 5;
    Factorial := 1;

    WHILE Counter > 1 DO
        Factorial := Factorial * Counter;
        DEC(Counter)
    END;

    Out.Int(Factorial,0)
END Factorial.

Maya Embedded Language

int $counter = 5;
int $factorial = 1;

while ($counter > 1) {
    $factorial *= $counter;
    $counter -= 1;
}

print("Factorial = " + $factorial + "\n");

Nim

var
  counter = 5            # Set counter value to 5
  factorial = 1          # Set factorial value to 1

while counter > 1:       # While counter is greater than 0
    factorial *= counter # Set new value of factorial to counter.
    dec counter          # Set the counter to counter - 1.

echo factorial

Non-terminating while loop:

while true:
  echo "Help! I'm stuck in a loop!"

Pascal

Pascal has two forms of the while loop, while and repeat-until. while repeats one statement (unless enclosed in a begin-end block) as long as the condition is true. repeat-until repetitively executes a block of one or more statements until the a condition is false. The main difference between the two is that while executes zero times if the condition is initially false, whereas repeat-until executes at least once.

program Factorial1;
var
    Fv: integer;

    procedure fact(counter:integer);
    var
        Factorial: integer;

    begin
         Factorial := 1;

         while Counter > 1 do
         begin
             Factorial := Factorial * Counter;
             Counter := Counter - 1
         end;

         WriteLn(Factorial)
     end;

begin
    Write('Enter a number to return its factorial: ');
    readln(fv);
    repeat
         fact(fv);
         Write('Enter another number to return its factorial (or 0 to quit): ');
     until fv=0;
end.

Perl

my $counter   = 5;
my $factorial = 1;

while ($counter > 1) {
    $factorial *= $counter--; # Multiply, then decrement
}

print $factorial;

While loops are frequently used for reading data line by line (as defined by the $/ line separator) from open filehandles:

open IN, "<test.txt";

while (<IN>) {
    print;
}

close IN;

PHP

$counter = 5;
$factorial = 1;

while ($counter > 1) {
    $factorial *= $counter--; // Multiply, then decrement.
}

echo $factorial;

PL/I

The PL/I DO statement can act as either a for loop, a while loop, or a do until loop.

declare counter   fixed initial(5);
declare factorial fixed initial(1);

do while(counter > 1)
    factorial = factorial * counter;
    counter = counter - 1;
end;

Python

counter = 5                           # Set the value to 5
factorial = 1                         # Set the value to 1

while counter > 1:                    # While counter(5) is greater than 0
    factorial *= counter              # Set new value of factorial to counter.
    counter -= 1                      # Set the counter to counter - 1.

print(factorial)                      # Print the value of factorial.

Non-terminating while loop:

while True:
    print("Help! I'm stuck in a loop!")

Racket

In Racket, as in other Scheme implementations, a named-let is a popular way to implement loops:

#lang racket
(define counter 5)
(define factorial 1)
(let loop ()
    (when (> counter 1)
        (set! factorial (* factorial counter))
        (set! counter (sub1 counter))
        (loop)))
(displayln factorial)

Using a macro system, implementing a while loop is a trivial exercise (commonly used to introduce macros):

#lang racket
(define-syntax-rule (while test body ...) ; implements a while loop
    (let loop () (when test body ... (loop))))
(define counter 5)
(define factorial 1)
(while (> counter 1)
    (set! factorial (* factorial counter))
    (set! counter (sub1 counter)))
(displayln factorial)

However, an imperative programming style is often discouraged in Scheme and Racket.

Ruby

# Count Down Variant
counter = 5
factorial = 1

while counter > 1
  factorial *= counter
  counter -= 1
end

puts factorial

# Count Up Variant
counter = 2
factorial = 1

while counter <= 5
  factorial *= counter
  counter += 1
end

puts factorial

Rust

fn main() {
    let mut counter = 5;
    let mut factorial = 1;

    while counter > 1 {
        factorial *= counter;
        counter -= 1;
    }

    println!("{}", factorial);
}

Smalltalk

Contrary to other languages, in Smalltalk a while loop is not a language construct but defined in the class BlockClosure as a method with one parameter, the body as a closure, using self as the condition.

Smalltalk also has a corresponding whileFalse: method.

| count factorial |
count := 5.
factorial := 1.
[count > 0] whileTrue:
    [factorial := factorial * count.
    count := count - 1].
Transcript show: factorial

Swift

var counter = 5                 // Set the initial counter value to 5
var factorial = 1               // Set the initial factorial value to 1

while counter > 1 {             // While counter(5) is greater than 0
    factorial *= counter        // Set new value of factorial to factorial x counter.
    counter -= 1                // Set the new value of counter to  counter - 1.
}

print(factorial)                // Print the value of factorial.

Tcl

set counter 5
set factorial 1

while {$counter > 1} {
    set factorial [expr $factorial * $counter]
    incr counter -1
}

puts $factorial

PowerShell

$counter = 5
$factorial = 1

while ($counter) {
    $factorial *= $counter--
}

$factorial

While (language)

While^[4] is a simple programming language constructed from assignments, sequential composition, conditionals, and while statements, used in the theoretical analysis of imperative programming language semantics.^[5]^[6]

C := 5;
F := 1;

while (C > 1) do
    F := F * C;
    C := C - 1;

Overview

Examples