Editing Control flow (section)

=== Count-controlled loops ===
{{main article|For loop}}
Most programming languages have constructions for repeating a loop a certain number of times.
In most cases counting can go downwards instead of upwards and step sizes other than 1 can be used.

{| class="wikitable"
|
 FOR I = 1 TO N
    xxx
 NEXT I
|
 '''for''' I := 1 '''to''' N '''do''' '''begin'''
    xxx
 '''end''';
|-
|
 DO I = 1,N
     xxx
 END DO
|
 '''for''' ( I=1; I<=N; ++I ) {
     xxx
 }
|}

In these examples, if N < 1 then the body of loop may execute once (with I having value 1) or not at all, depending on the programming language.

In many programming languages, only integers can be reliably used in a count-controlled loop. Floating-point numbers are represented imprecisely due to hardware constraints, so a loop such as<br />
    '''for''' X := 0.1 '''step''' 0.1 '''to''' 1.0 '''do'''

might be repeated 9 or 10 times, depending on rounding errors and/or the hardware and/or the compiler version. Furthermore, if the increment of X occurs by repeated addition, accumulated rounding errors may mean that the value of X in each iteration can differ quite significantly from the expected sequence 0.1, 0.2, 0.3, ..., 1.0.