C Programming switch Statement

Decision making are needed when, the program encounters the situation to choose a particular statement among many statements. If a programmer has to choose one block of statement among many alternatives, nested if...else can be used but, this makes programming logic complex. This type of problem can be handled in C programming using switch statement.

Syntax of switch...case

switch (n) {
case constant1:
 code/s to be executed if n equals to constant1;
 break;
case constant2:
 code/s to be executed if n equals to constant2;
 break;
 .
 .
 . 
default:
 code/s to be executed if n doesn't match to any cases;
}

The value of n is either an integer or a character in above syntax. If the value of n matches constant in case, the relevant codes are executed and control moves out of the switch statement. If the n doesn't matches any of the constant in case, then the default codes are executed and control moves out of switch statement.

Example of switch...case statement

Write a program that asks user an arithmetic operator('+','-','*' or '/') and two operands and perform the corresponding calculation on the operands.

/* C program to demonstrate the working of switch...case statement */
/* C Program to create a simple calculator for addition, subtraction, 
 multiplication and division */
# include 
int main() {
 char o;
 float num1,num2;
 printf("Select an operator either + or - or * or / \n");
 scanf("%c",&o);
 printf("Enter two operands: ");
 scanf("%f%f",&num1,&num2);
 switch(o) {
 case '+':
 printf("%.1f + %.1f = %.1f",num1, num2, num1+num2);
 break;
 case '-':
 printf("%.1f - %.1f = %.1f",num1, num2, num1-num2);
 break;
 case '*':
 printf("%.1f * %.1f = %.1f",num1, num2, num1*num2);
 break;
 case '/':
 printf("%.1f / %.1f = %.1f",num1, num2, num1/num2);
 break;
 default:
 /* If operator is other than +, -, * or /, error message is shown */
 printf("Error! operator is not correct");
 break;
 }
 return 0;
}

Output

Enter operator either + or - or * or / 
*
Enter two operands: 2.3
4.5
2.3 * 4.5 = 10.3

The break statement at the end of each case cause switch statement to exit. If break statement is not used, all statements below that case statement are also executed.