The `for`

statement or `for`

loop is useful while executing a statement multiple number of times.

The `for`

loop is the most commonly used statement in C++. This loop consists of three expression:

- The first
**expression**is used to initialize the index value - The second
**expression**is used to check whether or not the loop is to be continued again - The third
**expression**is used to change the index value for further iteration

The general form of `for`

statement is:

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for(expression 1; expression 2; expression 3) statement; |

In other words,

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for(initial condition; test condition; incrementer or decrementer) { statement1; statement2; ..... ..... } |

Where,

**expression 1**is the initialization of the expression or the condition called an index**expression 2**is the condition checked. As long as the given expression is true the loop statement will be repeated**expression 3**is the incrementer or decrementer to change the index value of the`for`

loop variable

Typically, **expression 1** is an assignment expression, **expression 2** is a logical expression and **expression 3** is a unary expression or an assignment expression.

When the `for`

statement is executed, **expression 2** is evaluated and tested at the begening of each pass through the loop and **expression 3** is evaluated at the end of each pass.

**Program to compute a sum of consecutive integers, i.e., the program to compute the sum 1 + 2 + 3 + .. + n, for an integer input n.**

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#include { int n; cout << "Enter a positive integer: "; cin >> n; long sum = 0; for(int i=1; i<=n; i++) { sum = sum + i; } cout << "Sum of first " << n << " integers is " << sum; } |

What will be the output of that above program?

Output:

Enter a positive integer: 3

Sum of first 3 integers is 6