C,
C++,
C#,
Java

while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the start of each iteration.

while (testCondition)
    statement(s)

Example

The following code prints a countdown from 10 to 1. Assume that a function called display() has been defined. Assume that it's the same thing as printf() in C, cout in C++, System.Console.WriteLine() in C# and System.out.println() in Java.

int count = 10;
while (count > 0) {
    display(count);
    count--;
}

Python

while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the start of each iteration.

while testCondition:
    statement(s)

Example

The following code prints a countdown from 10 to 1.

count = 10
while count > 0:
    print count
    count = count - 1

RB

do until loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to FALSE at the start of each iteration.

do until testCondition
    statement(s)
loop

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do until count = 0
    msgbox str(count)
    count = count - 1
loop

while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the start of each iteration.

while testCondition
    statement(s)
wend

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
while count > 0
    msgbox str(count)
    count = count - 1
wend

VB 6, VB .NET

do until loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to FALSE at the start of each iteration.

Do Until testCondition
    statement(s)
Loop

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do until count = 0
    msgbox str(count)
    count = count - 1
loop

do while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the start of each iteration.

Do While testCondition
    statement(s)
Loop

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do while count > 0
    msgbox str(count)
    count = count - 1
loop

while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the start of each iteration. This loop differs slightly in VB6 and VB .NET.

' VB6
While testCondition
    statement(s)
Wend

' VB .NET
While testCondition
    statement(s)
End While

Note that the end of a while loop is the non-word wend in VB6 and the more consistent end while in VB .NET.

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
while count > 0
    msgbox str(count)
    count = count - 1
wend 'end while in VB .NET

C,
C++,
C#,
Java

do...while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the end of each iteration.

do something
    statement(s)
while (testCondition);

Example

The following code prints a countdown from 10 to 1.

int count = 10;
do {
    display(count);
    count = count - 1;
}
while (count >= 1);

Python

Use while loops with a break statement

Python has no "post-test" loops. Rewrite the loop so that if performs the test at the start, or if you must perform the test at the end, use an if statement containing a break at the end of a loop.

Example

The following code prints a countdown from 10 to 1.

count = 10
while 1:
    print count
    count = count - 1
    if count < 1:
        break

RB

do...until loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to FALSE at the end of each iteration.

do
    statement(s)
loop until testCondition

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do
    msgbox str(count)
    count = count - 1
loop until count < 1

VB 6, VB .NET

do...loop until loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to FALSE at the end of each iteration.

Do
  something
Loop Until testCondition

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do
    msgbox str(count)
    count = count - 1
loop until count < 1

do...loop while loop

The set of statements in the loop are executed repeatedly as long as the test condition evaluates to TRUE at the end of each iteration.

Do
  something
Loop While testCondition

Example

The following code prints a countdown from 10 to 1.

dim count as integer
count = 10
do
    msgbox str(count)
    count = count - 1
loop while count >= 1

C,
C++,
C#,
Java

for loop

The basic for loop has the following structure:

for (counter = startValue; continueCondition; change)
    statement(s)

A one-time variable initialization is performed at the start of the loop. Each time the loop cycles to the beginning, the continueCondition is evaluated. The statement(s) are execute if and only if the continueCondition evaluates to true.

Counting upwards from a to b:

for (i = a; i <= b; i++)
    statement(s)

Counting downwards from a to b:

for (i = a; i >= b; i --)
    statement(s)

Python

for loop

The for loop has the following structure:

for currentItem in sequence
    statement(s)

Python's for loop is different from most other languages' versions. While the for loop in most programming languages makes a variable count from a start value to an end value, Python's for loop sets a variable to iterates through a sequence of items (such as a list or string). This approach, while unusual, is a good fit for a large number of programming tasks.

In order to make a Python for loop count like for loops in other languages, use Python's range() function to create a sequence of numbers through which it will iterate.

Counting upwards from a to b:

for i in range(a, b+1):
    statement(s)

Counting downwards from a to b:

for i in range(a, b-1, -1):
    statement(s)

RB

For loop

The for loop has the following structure:

for counter = startValue to endValue [step stepSize]
    statement(s)
next

Counting upwards from a to b:

for i = a to b
    statement(s)
next

Counting downwards from a to b:

for i = a downto b
    statement(s)
next

VB

For loop

The for loop has the following structure:

for counter = startValue to endValue [step stepSize]
    statement(s)
next [counter]

Counting upwards from a to b:

For i = a To b
    statement(s)
Next

Counting downwards from a to b:

For i = a To b Step -1
    statement(s)
Next

C,
C++,
Java

No equivalent.

C#

foreach loop

foreach (item in group)
    statement(s)

The group can be any container class that supports the IEnumerable interface (such as arrays and collection classes).

Example

The following code creates an array of numbers and then uses a foreach loop to print them out.

int[] myNumbers = {2, 4, 6, 8, 10}
foreach (int currentNumber in myNumbers) {
    Console.WriteLine(temp);
}

Note that changing the contents variable holding the current item will not change the item in the group you're iterating through:

int[] myNumbers = {2, 4, 6, 8, 10}
foreach (int currentNumber in myNumbers) {
   currentNumber++;
   Console.WriteLine(temp);
}

Python

for loop

Python's for loop is equivalent to other languages' foreach loops.

for currentItem in sequence
    statement(s)

The group can be any sequence (strings, lists and tuples are sequences).

RB

No equivalent.

VB 6, VB .NET

For Each loop

The for each loop has the following structure:

for each item in group
    statement(s)
next

The group can be a collection or an array. The statement(s) are executed if and only if the group contains at least one element -- if it's empty or hasn't yet been dimensioned, the result is an error.

C,
C++,
C#

break statement

When encountered inside a loop, program control is transferred to the line immediately following the end of the loop.

start of loop
    break;
end of loop

while (porridge > 0) {

    // some code here

    if (bearsAreNearby())
        break;

    // more code here

}

Java

break statement

When encountered inside a loop, program control is transferred to the line immediately following the end of the loop.

Java's break statement is more versatile than those for the other C-based languages, since it supports named breaks.

Python

break statement

When encountered inside a loop, program control is transferred to the line immediately following the end of the loop.

RB

Exit statement

When encountered inside a loop, program control is transferred to the line immediately following the end of the loop.

Exit

VB

Exit Do statement

When encountered inside a do loop, program control is transferred to the line immediately following the end of the loop.

Exit Do

Exit For statement

When encountered inside a for loop, program control is transferred to the line immediately following the end of the loop.

Exit For

C-based languages,
Python

for (int i = 1; i <= 10; i++) {

    // Code that we want to use
    // whether i is even or odd

    if (i % 2 = 1)
        continue;

    // Code that we want to use
    // only if i is even

}

C-based languages,
Python

for (int i = 1; i <= 10; i++) {

    // Code that we want to use
    // whether i is even or odd

    if (i % 2 = 1)
        continue;

    // Code that we want to use
    // only if i is even

}