Explain Loops – While loop, Do-while loop, for loop.

Loops are used to carry out certain instruction(s) in continuation for a fixed no of times.

Syntax of while loop:

//initialization stmt(s)

while (condition)
{
           //stmt1;
           //stmt2;
           ….
           ….
}

e.g.
x = 0; // initialization stmt
while (x < 10)
{
          cout << x<<”\n”;
          x ++;
}

This prints nos 0 to 9 on the screen.

Do- while loop:

This is similar to while loop; the only difference is unlike while loop, in do-while loop condition is checked after the loop statements are executed. This means the statements in the do while loop are executed at least once; even if the condition fails for the first time itself.

//initialization stmt(s)

do
{
        Stmt1;
        Stmt2;
} while (condition)

e.g.
x = 0;         // initialization stmt
do
{
        cout << x<<”\n”;
        x ++;
}while (x < 10);

This prints numbers 0 through 9 on the screen.

The for loop:

It does exactly the same thing as while loop; only difference is the initialization, the condition stmt is written on the same line.

for loop:

This is used when we want to execute certain statements for a fixed no of times. This is achieved by initializing a loop counter to a value and increasing or decreasing the value for certain no of times until a condition is satisfied. The loop statements are executed once for every iteration of the for loop.

for (initialize loop counter; condition checking; increasing/decreasing loop counter)
{
            //stmt1;
            //stmt2;
}

for (x = 0; x < 10; x++)
{
            cout <<<”\n”;
}

This code snippet will print nos 0 to 9.