Control Flow#

If-Else Statements#

The C programming language supports if-else statements for conditional code execution. They have the following syntax:

if (expression) statement
if (expression) statement else statement

The statement of the if is executed whenever expression is different from zero and the statement of the else is executed whenever expression is zero.

Switch Statements#

The C programming language supports switch statements for conditional code execution when multiple possible branches are possible. It has the following syntax:

switch (expression) statement

The expression must evaluate to an integer. The statement consists of zero or more case labeled statements and zero or one default labeled statement.

case constant-expression : statement
default : statement

The switch evaluates its expression, jumps to the case whose constant-expression matches expression and proceeds to execution. This means that all subsequent case statements are also executed. If this is not desired, a break statement should be at the end of each case. The switch statement jumps to default if no case matches and similarly proceeds with execution.

switch (month)
{
    case 1:  printf("January"); break;
    case 2:  printf("February"); break;
    case 3:  printf("March"); break;
    case 4:  printf("April"); break;
    case 5:  printf("May"); break;
    case 6:  printf("June"); break;
    case 7:  printf("July"); break;
    case 8:  printf("August"); break;
    case 9:  printf("September"); break;
    case 10: printf("October"); break;
    case 11: printf("November"); break;
    case 12: printf("December"); break;
    default: printf("No such month!"); break;
}

While Loops#

The C programming language provides while statements for repeated code execution Its syntax is the following:

while (expression) statement

The while statement executes statement as long as expression does not evaluate to zero.

Do-While Loops#

A do-while statement is like a while loop but it guarantees that its statement will be executed at least once.

do statement while (expression);

For Loops#

A for statement provides more complex loop functionality. Its syntax is the following:

for (expression1; expression2; expression3) statement

All expressions are optional.

First, expression1 is evaluated only once. Then, statement is executed repeatedly as long as expression2 is non-zero. After each execution, expression3 is evaluated.