Loop control statements in c are used to perform looping operations until the given condition is true. Control comes out of the loop statements once condition becomes false. Loops are used to repeat a block of code.
There are 3 types of loop control statements in C language. They are,
1. while
2. do-while
3. for
- While statement:
The while statement continuously executes a block of statements until given condition is false.
–> The while loop evaluates the test expression.
–> If the test expression is true, codes inside the body of while loop is evaluated.
–> Then, the test expression is evaluated again. This process goes on the test expression is false.
–> When the test expression is false, while loop is terminated.
Syntax:
while(expression)
{
statement(s)
}
Example:
#include<iostream>
using namespace std;
void main()
{
int num, i=1, factorial=1;
cout<<“Enter a positive integer:”;
cin>>number;
while (i<=number)
{
factorial=factorial*i’
i++;
}
cout<<“Factorial of “<<number<<“=”<<factorial;
} - do…while Loop:
The do…while loop is a variant of the while loop with one important difference. The body of do…while loop is executed at least once. Then, only the test expression is checked.
–> The code inside while loop is executed at least once. Then the test expression is checked.
–> If the test expression is true, then the body of loop is executed. This process continues until the test expression becomes false.
–> When the test expression is false, do…while loop is terminated.
Syntax:
do
{
statements;
}while(test_Expression);
Example:
#include<iostream>
using namespace std;
void main()
{
float sum=0.0, num;
do
{
cout<<“Enter a number:”;
cin>>num;
sum+=num; //sum=sum+num
}while(num!=0.0)
cout<<“Total sum=”<<sum
} - for Loop:
A for loop is a repetition control structure that allows to write a loop that needs to execute a specific number of times.
–> The initialization is executed once at the beginning.
–> Then, the test expression is evaluated.
–> If the test expression is false, for loop is terminated. But if the test expression is true, code inside the loop is executed and the expression is updated.
–> Again, the test expression is evaluated and this process is repeated until the test expression is false.
Syntax:
for(initialization; condition; increment/decrement)
{
statements;
}
Example:
#include<iostream>
using namespace std;
void main()
{
int i, n, fact=1;
cout<<“Enter a positive integer:”
cin>>n;
for(i=1; i<=n; i++)
{
fact*=i; //fact=fact*i
}
cout<<“Factorial of “<<n<<“=”<<fact;
}