The For Statement in C programming

The For Statement

The for repetition statement handles all the details of counter-controlled repetition. The general format of the for statement:

``````
for ( exp1; exp2; exp3  ) {
statement
}
``````

Often, exp1 and exp3 are comma-separated lists of expressions. The commas as used here are actually comma operators that guarantee that lists of expressions evaluate from left to right.

The value and type of a comma-separated list of expressions are the value and type of the rightmost expression in the list.

The following code demonstrates the for statement:

``````
// Summation with for (odd numbers from 2 to 100)
#include <stdio.h>
// function main begins program execution
int main( void )
{
unsigned int sum = 0; // initialize sum
unsigned int number;  // number to be added to sum
for ( number = 2; number <= 100; number += 2 ) {
sum += number; // add number to sum
} // end for
printf( "Sum is %u\n", sum ); // output sum
} // end function main
``````
``````
Output:
Sum is : 2550
``````

Another example using the For Statement

The c program below demonstrates the use of for statement to calculate the compound interest.

``````
// Calculating compound interest
#include <stdio.h>
#include <math.h>
// function main begins program execution
int main( void )
{
double amount; // amount on deposit
double principal = 1000.0; // starting principal
double rate = .05; // annual interest rate
unsigned int year; // year counter
printf( "%4s%21s\n", "Year", "Amount on deposit" );
// calculate amount on deposit for each of ten years
for ( year = 1; year <= 10; ++year ) {
// calculate new amount for specified year
amount = principal * pow( 1.0 + rate, year );
// output one table row
printf( "%4u%21.2f\n", year, amount );
} // end for
} // end function main
``````
``````
Output:
Year  Amount on deposite
1		1050.00
2		1102.50
3		1157.63
4		1215.51
5		1276.28
6		1340.10
7		1407.10
8		1477.46
9		1551.33
10		1628.89
``````

Note: This example made use of the <math.h> library, which we will discuss in C Math tutorial.

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