C switch Statement

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C switch Statement

C Decision Making

The switch statement is a restricted control flow statement that is used to execute different code blocks based on the value of an expression.

A switch statement allows testing a variable for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case.

Syntax

The syntax for a switch statement in C programming language is as follows:

switch(expression){
    case constant-expression :
       statement(s);
       break; /* optional */
    case constant-expression :
       statement(s);
       break; /* optional */
    
    /* you can have any number of case statements */
    default : /* Optional */
       statement(s);
}

Explanation of switch statement:

The value of the expression following the switch is compared with the constant value after each case until a match is found or execution reaches the default (if it exists).
If a match is found, the code block following the corresponding case is executed, and then the switch statement is exited.
If there is no match and a default exists, the code block following the default is executed.
If there is no match and no default, the entire switch statement is skipped until the end.

The switch statement must follow the following rules:

Type of switch expression: The expression in a switch statement must be an integer type (char, short, int, or an enumeration), or an expression that can be implicitly converted to an integer type.
Uniqueness of case labels: In a switch statement, each case label must be unique; there cannot be duplicate values.
Optionality of the default case: The default label in a switch statement is optional. If no case label matches, the code block under the default label is executed (if it exists).
Constant value in case labels: The value following the case label must be a constant expression, meaning its value can be determined at compile time.
Order of case labels: The order of case labels in a switch statement is not important; they can be written in any order. The program will match them in the order they appear.
Use of the break statement: Usually, a break statement is needed at the end of the code block for each case label to terminate the execution of the switch statement. Without a break statement, the program will continue executing the code in the next case label until it encounters a break statement or the switch statement ends.
Nesting of switch statements: Switch statements can be nested within other switch statements, but attention should be paid to code readability and complexity.
Scope of case labels and expressions: The case labels of a switch statement can be integer constant expressions, but they cannot be floating-point numbers or strings.

Flow Diagram

switch statement in C

Example

#include <stdio.h>

int main() {
   /* local variable definition */
   char grade = 'B';

   switch(grade) {
      case 'A' :
         printf("Excellent!n" );
         break;
      case 'B' :
      case 'C' :
         printf("Well donen" );
         break;
      case 'D' :
         printf("You passedn" );
         break;
      case 'F' :
         printf("Better try againn" );
         break;
      default :
         printf("Invalid graden" );
   }
   
   printf("Your grade is  %cn", grade );

   return 0;
}

When the above code is compiled and executed, it produces the following result:

Well done
Your grade is  B

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#0 Helen

QQ9***13813@163.com

Reference Link

Use the switch statement to write a program that determines if a given year is a leap year based on the input year, and determines the number of days in that month based on the input month.

Definition of a leap year:

An ordinary year (a year not divisible by 100) is a leap year if it is divisible by 4. (e.g., 2004 is a leap year, 1999 is not).
A century year (a year divisible by 100) is a leap year if it is divisible by 400. (e.g., 2000 is a leap year, 1900 is not).

#include <stdio.h>
int main() {
   int year, month, flag = 0;
   printf("Please enter the year and month, separated by a space:!n");
   scanf("%d %d", &year, &month);
   if( ( year % 4 ==0 && year % 100 != 0 ) || year % 400 ==0) {
      flag = 1;
      printf("The year you entered is a leap yearn");
   } else {
      flag = 0;
      printf("The year you entered is a common year!!n");
   }
   switch(month) {
      case 1: printf("The month you entered is January with 31 daysn"); break;
      case 2:
         if(flag == 1)
            printf("The month you entered is February with 29 daysn");
         else
            printf("The month you entered is February with 28 daysn");
         break;
      case 3: printf("The month you entered is March with 31 daysn"); break;
      case 4: printf("The month you entered is April with 30 daysn"); break;
      case 5: printf("The month you entered is May with 31 daysn"); break;
      case 6: printf("The month you entered is June with 30 daysn"); break;
      case 7: printf("The month you entered is July with 31 daysn"); break;
      case 8: printf("The month you entered is August with 31 daysn"); break;
      case 9: printf("The month you entered is September with 30 daysn"); break;
      case 10: printf("The month you entered is October with 31 daysn"); break;
      case 11: printf("The month you entered is November with 30 daysn"); break;
      case 12: printf("The month you entered is December with 31 daysn"); break;
   }
   return 0;
}

Helen

8 years ago (2018-04-22)

#0 Shadow Eagle

323***0161@qq.com

Use switch statement

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C switch Statement

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C switch Statement

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3 Notes

#0 Helen

#0 Shadow Eagle

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