Author: saqibkhan

In C, a switch case is a control flow statement used to compare a variable with specific values and execute different blocks of code depending on which value matches. For example −

switch(num){case1:printf("One");break;case2:printf("Two");break;default:printf("Other");}

Here, the switch case checks exact matches only. But sometimes, we want to check if a value falls within a range, like 1-5 or ‘A’-‘Z’. Instead of writing a separate case for each value, we can define a range of values in a single case. This is called a switch case with ranges. For exmaple −

switch(num){case1...5:printf("Between 1 and 5");break;case6...10:printf("Between 6 and 10");break;default:printf("Other");}

Switch Case Using Range

A switch case using ranges handles multiple consecutive values in one case. Instead of writing a separate case for each number or character, we define a range and the same block of statements runs for all values in that range.

We cannot use ranges in standard C, but the GNU C compiler provides this feature as a case range extension.

Syntax for Switch Case Using Range

Following is the syntax for using ranges in a switch case statement.

switch(value){case lower_range ... higher_range:// code blockbreak;default:// code block}

Here, lower_range is the starting value and higher_range is the ending value. We must put spaces around the ellipsis (…) to make a valid syntax.

Steps to Implement Range Handling

To implement switch case with range handling, we first group the variable into categories and then use the switch to check which category it belongs to. Here’s how we handle ranges-

• First, we use if statements to check which range the value belongs to, like 1-10, 11-20, or 21-30.
• Then, we assign each range a number, such as 1, 2, or 3, to represent it.
• Next, pass this number to the switch case where each case corresponds to one range.
• The switch case checks the number and runs the code for that range.
• Finally, we add a default case to handle values outside the defined ranges.

Example: Simple Range Check

Let’s see a simple example where we will use two ranges inside the switch case and check if a number belongs to the range 1-5 or 6-10. If it does not belong to any of these ranges, then the default statement will get printed.

#include <stdio.h>intmain(){int number =7;// You can change the value to test different casesswitch(number){case1...5:printf("The number is between 1 and 5.\n");break;case6...10:printf("The number is between 6 and 10.\n");break;default:printf("The number is outside the range 1 to 10.\n");}return0;}

Following is the output of the above program −

The number is between 6 and 10.

Example: Using if-else for Ranges with Switch Case

In this example, we check which range a number belongs to and display a message. We first use if-else statements to assign the number to a range such as 1-10, 11-20, 21-30, or out of range, and then the switch case prints the message corresponding to that range.

#include <stdio.h>intmain(){int number =17;// Set the number directly// Normalize the number into a rangeint range;if(number >=1&& number <=10){
  range =1;// Range 1-10}elseif(number &gt;=11&amp;&amp; number &lt;=20){
  range =2;// Range 11-20}elseif(number &gt;=21&amp;&amp; number &lt;=30){
  range =3;// Range 21-30}else{
  range =4;// Out of range}// Use switch to handle the different rangesswitch(range){case1:printf("The number is between 1 and 10\n");break;case2:printf("The number is between 11 and 20\n");break;case3:printf("The number is between 21 and 30\n");break;default:printf("The number is out of range\n");}return0;}</code></pre>


Following is the output of the above program, showing which range the given number belongs to.



The number is between 11 and 20




Example: Handling Character Ranges in Switch Case



In this example, we check what type of character a variable contains. The switch case checks whether the character is a lowercase letter, an uppercase letter, or a digit, and prints the corresponding message. Any character outside these ranges is handled by the default case.



#include <stdio.h>intmain(){char ch ='G';// Set the character directly// Switch-case with rangesswitch(ch){case'a'...'z':// Lowercase letters rangeprintf("%c is a lowercase alphabet\n", ch);break;case'A'...'Z':// Uppercase letters rangeprintf("%c is an uppercase alphabet\n", ch);break;case'0'...'9':// Digits rangeprintf("%c is a digit\n", ch);break;default:printf("%c is a non-alphanumeric character\n", ch);}return0;}



Below is the output of the above program where it shows the type of the given character.



G is an uppercase alphabet




Example: Using Category Mapping with Switch Case



In this example, we group marks into categories by dividing them by 10. For example, marks from 90 to 100 fall into category 9 or 10, marks from 80 to 89 fall into category 8, and so on. Then, the switch case prints the message for that category.



#include <stdio.h>intmain(){int marks =87;// Set the marks directly// Convert marks into categories (divide by 10)int category = marks /10;// Handle ranges using switchswitch(category){case10:// For 100case9:// For 90-99printf("Excellent! Grade A\n");break;case8:// For 80-89printf("Very Good! Grade B\n");break;case7:// For 70-79printf("Good! Grade C\n");break;case6:// For 60-69printf("Satisfactory! Grade D\n");break;default:// For below 60printf("Needs Improvement! Grade F\n");}return0;}



Below is the output of the program, which divides the given marks and shows their category.



Very Good! Grade B




Errors in Switch Case Using Ranges



When using ranges in switch case, there are a few important things to keep in mind −



Invalid Range (low > high): If the low value is greater than the high value, the compiler will give an error.



Example of incorrect range −



case5...1:// This will cause an error



Overlapping Ranges: If you try to define multiple case ranges that overlap, the compiler will give an error.



Example of incorrect overlapping ranges −



case1...5:case3...7:// Overlap error



In this chapter, we learned how to use ranges with switch cases to handle multiple consecutive values together. We covered this for both numbers and characters, and also looked at situations where errors can occur.

It is possible to have a switch as a part of the statement sequence of an outer switch. Even if the case constants of the inner and outer switch contain common values, no conflicts will arise.

Syntax

The syntax for a nested switch statement is as follows −

switch(ch1){case'A':printf("This A is part of outer switch");switch(ch2){case'A':printf("This A is part of inner switch");break;case'B':/* case code */}break;case'B':/* case code */}

Example

Take a look at the following example −

#include <stdio.h>intmain(){/* local variable definition */int a =100;int b =200;switch(a){case100:printf("This is part of outer switch\n", a);switch(b){case200:printf("This is part of inner switch\n", a);}}printf("Exact value of a is: %d\n", a);printf("Exact value of b is: %d\n", b);return0;}

Output

When the above code is compiled and executed, it produces the following output −

This is part of outer switch
This is part of inner switch
Exact value of a is : 100
Exact value of b is : 200

Nested Switch-Case Statements in C

Just like nested ifelse, you can have nested switch-case constructs. You may have a different switch-case construct each inside the code block of one or more case labels of the outer switch scope.

The nesting of switch-case can be done as follows −

switch(exp1){case val1:switch(exp2){case val_a:
     stmts;break;case val_b:
     stmts;break;}case val2:switch(expr2){case val_c:
     stmts;break;case val_d:
     stmts;break;}}</code></pre>


Example



Here is a simple program to demonstrate the syntax of Nested Switch Statements in C −



#include <stdio.h>intmain(){int x =1, y ='b', z='X';// Outer Switchswitch(x){case1:printf("Case 1 \n");switch(y){case'a':printf("Case a \n");break;case'b':printf("Case b \n");break;}break;case2:printf("Case 2 \n");switch(z){case'X':printf("Case X \n");break;case'Y':printf("Case Y \n");break;}}return0;}



Output



When you run this code, it will produce the following output −



Case 1 
Case b




Change the values of the variables (x, y, and z) and check the output again. The output depends on the values of these three variables.

A switch statement allows a variable to be tested 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.

C switch-case Statement

The switch-case statement is a decision-making statement in C. The if-else statement provides two alternative actions to be performed, whereas the switch-case construct is a multi-way branching statement. A switch statement in C simplifies multi-way choices by evaluating a single variable against multiple values, executing specific code based on the match. It allows a variable to be tested for equality against a list of values.

Syntax of switch-case Statement

The flow of the program can switch the line execution to a branch that satisfies a given case. The schematic representation of the usage of switch-case construct is as follows −

switch(Expression){// if expr equals Value1case Value1: 
  Statement1;
  Statement2;break;// if expr equals Value2case Value2: 
  Statement1;
  Statement2;break;..// if expr is other than the specific values abovedefault:
  Statement1;
  Statement2;}</code></pre>


How switch-case Statement Work?



The parenthesis in front of the switch keyword holds an expression. The expression should evaluate to an integer or a character. Inside the curly brackets after the parenthesis, different possible values of the expression form the case labels.



One or more statements after a colon(:) in front of the case label forms a block to be executed when the expression equals the value of the label.



You can literally translate a switch-case as "in case the expression equals value1, execute the block1", and so on.



C checks the expression with each label value, and executes the block in front of the first match. Each case block has a break as the last statement. The break statement takes the control out of the scope of the switch construct.



You can also define a default case as the last option in the switch construct. The default case block is executed when the expression doesnt match with any of the earlier case values.



Flowchart of switch-case Statement



The flowchart that represents the switch-case construct in C is as follows −







Rules for Using the switch-case Statement



The following rules apply to a switch statement −




The expression used in a switch statement must have an integral or enumerated type, or be of a class type in which the class has a single conversion function to an integral or enumerated type.



You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.



The constant-expression for a case must be the same data type as the variable in the switch, and it must be a constant or a literal.



When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.



When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.



Not every case needs to contain a break. If no break appears, the flow of control will fall through to subsequent cases until a break is reached.



A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case.




The switch-case statement acts as a compact alternative to cascade of if-else statements, particularly when the Boolean expression in "if" is based on the "=" operator.



If there are more than one statements in an if (or else) block, you must put them inside curly brackets. Hence, if your code has many if and else statements, the code with that many opening and closing curly brackets appears clumsy. The switch-case alternative is a compact and clutter-free solution.



C switch-case Statement Examples



Practice the following examples to learn the switch case statements in C programming language −



Example 1



In the following code, a series of if-else statements print three different greeting messages based on the value of a "ch" variable ("m", "a" or "e" for morning, afternoon or evening).



#include <stdio.h>intmain(){/* local variable definition */char ch ='e';printf("Time code: %c\n\n", ch);if(ch =='m')printf("Good Morning");elseif(ch =='a')printf("Good Afternoon");elseprintf("Good Evening");return0;}



The if-else logic in the above code is replaced by the switch-case construct in the code below −



#include <stdio.h>intmain(){// local variable definitionchar ch ='m';printf("Time code: %c\n\n", ch);switch(ch){case'a':printf("Good Afternoon\n");break;case'e':printf("Good Evening\n");break;case'm':printf("Good Morning\n");}return0;}



Output



Change the value of "ch" variable and check the output. For ch = 'm', we get the following output −



Time code: m

Good Morning




The use of break is very important here. The block of statements corresponding to each case ends with a break statement. What if the break statement is not used?



The switch-case works like this: As the program enters the switch construct, it starts comparing the value of switching expression with the cases, and executes the block of its first match. The break causes the control to go out of the switch scope. If break is not found, the subsequent block also gets executed, leading to incorrect result.



Example 2: Switch Statement without using Break



Let us comment out all the break statements in the above code.



#include <stdio.h>intmain(){/* local variable definition */char ch ='a';printf("Time code: %c\n\n", ch);switch(ch){case'a':printf("Good Afternoon\n");// break;case'e':printf("Good Evening\n");// break;case'm':printf("Good Morning\n");}return0;}



Output



You expect the "Good Morning" message to be printed, but you find all the three messages printed!



Time code: a

Good Afternoon
Good Evening
Good Morning




This is because C falls through the subsequent case blocks in the absence of break statements at the end of the blocks.



Example 3: Grade Checker Program using Switch Statement



In the following program, "grade" is the switching variable. For different cases of grades, the corresponding result messages will be printed.



#include <stdio.h>intmain(){/* local variable definition */char grade ='B';switch(grade){case'A':printf("Outstanding!\n");break;case'B':printf("Excellent!\n");break;case'C':printf("Well Done\n");break;case'D':printf("You passed\n");break;case'F':printf("Better try again\n");break;default:printf("Invalid grade\n");}printf("Your grade is  %c\n", grade);return0;}



Output



Run the code and check its output −



Excellent!
Your grade is  B




Now change the value of "grade" (it is a "char" variable) and check the outputs.



Example 4: Menu-based Calculator for Arithmetic Operations using Switch



The following example displays a menu for arithmetic operations. Based on the value of the operator code (1, 2, 3, or 4), addition, subtraction, multiplication or division of two values is done. If the operation code is something else, the default case is executed.



#include <stdio.h>intmain(){// local variable definitionint a =10, b =5;// Run the program with other values 2, 3, 4, 5int op =1;float result;printf("1: addition\n");printf("2: subtraction\n");printf("3: multiplication\n");printf("4: division\n");printf("\na: %d b: %d : op: %d\n", a, b, op);switch(op){case1:
     result = a + b;break;case2:
     result = a - b;break;case3:
     result = a * b;break;case4:
     result = a / b;break;default:printf("Invalid operation\n");}if(op &gt;=1&amp;&amp; op &lt;=4)printf("Result: %6.2f", result);return0;}</code></pre>


Output



1: addition
2: subtraction
3: multiplication
4: division

a: 10 b: 5 : op: 1
Result:  15.00




For other values of "op" (2, 3, and 4), you will get the following outputs −



a: 10 b: 5 : op: 2
Result:   5.00

a: 10 b: 5 : op: 3
Result:  50.00

a: 10 b: 5 : op: 4
Result:   2.00

a: 10 b: 5 : op: 5
Invalid operation




Switch Statement by Combining Multiple Cases



Multiple cases can be written together to execute one block of code. When any of them case value matches, the body of these combined cases executes. If you have a situation where the same code block is to be executed for more than one case labels of an expression, you can combine them by putting the two cases one below the other, as shown below −



Syntax



switch(exp){case1:case2:
  statements;break;case3:
  statements;break;default:printf("%c is a non-alphanumeric character\n", ch);}</code></pre>


You can also use the ellipsis () to combine a range of values for an expression. For example, to match the value of switching variable with any number between 1 to 10, you can use "case 1 10"



Example 1



#include <stdio.h>intmain(){// local variable definitionint number =5;switch(number){case1...10:printf("The number is between 1 and 10\n");break;default:printf("The number is not between 1 and 10\n");}return0;}



Output



Run the code and check its output. For "number = 5", we get the following output −



The number is between 1 and 10




Example 2



The following program checks whether the value of the given char variable stores a lowercase alphabet, an uppercase alphabet, a digit, or any other key.



#include <stdio.h>intmain(){char ch ='g';switch(ch){case'a'...'z':printf("%c is a lowercase alphabet\n", ch);break;case'A'...'Z':printf("%c is an uppercase alphabet\n", ch);break;case48...57:printf("%c is a digit\n", ch);break;default:printf("%c is a non-alphanumeric character\n", ch);}return0;}



Output



For ch = 'g', we get the following output −



g is a lowercase alphabet




Test the code output with different values of "ch".

It is always legal in C programming to nest if-else statements, which means you can use one if or else-if statement inside another if or else-if statement(s).

In the programming context, the term “nesting” refers to enclosing a particular programming element inside another similar element. For example, nested loops, nested structures, nested conditional statements, etc. If an if statement in C is employed inside another if statement, then we call it as a nested if statement in C.

Syntax

The syntax of nested if statements is as follows −

if(expr1){if(expr2){
  block to be executed when 
  expr1 and expr2 are true
   }else{
  block to be executed when 
  expr1 is true but expr2 is false
   }}

The following flowchart represents the nesting of if statements −

You can compound the Boolean expressions with && or || to get the same effect. However, for more complex algorithms, where there are different combinations of multiple Boolean expressions, it becomes difficult to form the compound conditions. Instead, it is recommended to use nested structures.

Another if statement can appear inside a top-level if block, or its else block, or inside both.

Example 1

Let us take an example, where the program needs to determine if a given number is less than 100, between 100 to 200, or above 200. We can express this logic with the following compound Boolean expression −

#include <stdio.h>intmain(){// local variable definitionint a =274;printf("Value of a is : %d\n", a);if(a <100){printf("Value of a is less than 100\n");}if(a >=100&& a <200){printf("Value of a is between 100 and 200\n");}if(a >=200){printf("Value of a is more than 200\n");}}

Output

Run the code and check its output. Here, we have intialized the value of “a” as 274. Change this value and run the code again. If the supplied value is less than 100, then you will get a different output. Similarly, the output will change again if the supplied number is in between 100 and 200.

Value of a is : 274
Value of a is more than 200

Example 2

Now let’s use nested conditions for the same problem. It will make the solution more understandable when we use nested conditions.

First, check if “a >= 100”. Inside the true part of the if statement, check if it is <200 to decide if the number lies between 100-200, or it is >200. If the first condition (a >= 100) is false, it indicates that the number is less than 100.

#include <stdio.h>intmain(){// local variable definition// check with different values 120, 250 and 74int a =120;printf("value of a is : %d\n", a );// check the boolean conditionif(a >=100){// this will check if a is between 100-200if(a <200){// if the condition is true, then print the followingprintf("Value of a is between 100 and 200\n");}else{printf("Value of a is more than 200\n");}}else{// executed if a < 100printf("Value of a is less than 100\n");}return0;}

Output

Run the code and check its output. You will get different outputs for different input values of “a” −

Value of a is : 120
Value of a is between 100 and 200

Example 3

The following program uses nested if statements to determine if a number is divisible by 2 and 3, divisible by 2 but not 3, divisible by 3 but not 2, and not divisible by both 2 and 3.

#include <stdio.h>intmain(){int a =15;printf("a: %d\n", a);if(a %2==0){if(a %3==0){printf("Divisible by 2 and 3");}else{printf("Divisible by 2 but not 3");}}else{if(a %3==0){printf("Divisible by 3 but not 2");}else{printf("Not divisible by 2, not divisible by 3");}}return0;}

Output

Run the code and check its output −

a: 15
Divisible by 3 but not 2

For different values of “a”, you will get different outputs.

Example 4

Given below is a C program to check if a given year is a leap year or not. Whether the year is a leap year or not is determined by the following rules −

• Is the year divisible by 4?
• If yes, is it a century year (divisible by 100)?
• If yes, is it divisible by 400? If yes, it is a leap year, otherwise not.
• If it is divisible by 4 and not a century year, it is a leap year.
• If it is not divisible by 4, it is not a leap year.

Here is the C code −

#include <stdio.h>intmain(){// Test the program with the values 1900, 2023, 2000, 2012int year =1900;printf("year: %d\n", year);// is divisible by 4?if(year %4==0){// is divisible by 100?if(year %100==0){// is divisible by 400?if(year %400==0){printf("%d is a Leap Year\n", year);}else{printf("%d is not a Leap Year\n", year);}}else{printf("%d is not a Leap Year\n", year);}}else{printf("%d is a Leap Year\n", year);}}

Output

Run the code and check its output −

year: 1900
1900 is not a Leap Year

Test the program with different values for the variable “year” such as 1900, 2023, 2000, 2012.

The same result can be achieved by using the compound Boolean expressions instead of nested if statements, as shown below −

If(year %4==0&&(year %400==0|| year %100!=0)){printf("%d is a leap year", year);}else{printf("%d is not a leap year", year);}

With nested if statements in C, we can write structured and multi-level decision-making algorithms. They simplify coding the complex discriminatory logical situations. Nesting too makes the program more readable, and easy to understand.