Switch case in c

What is switch case in c programming?

Switch case block allows to execute a set of code among other sets of code.

Switch case are the keywords used to write switch case block in c.

Switch statement is a multiway branching statement.

Expression specified in switch case block should result in constant else it is not valid.

Switch statements can be nested. It means you can nest switch case in another switch statements. Nesting of switch statements is not a good programming concept. Nesting of switch case statements reduces the readability of the program and increases the complexity.

Syntax of switch case in c

switch (expression)
{
 case case_constant1 ://set of statements for case_constant1
  break;
 case case_constant2 ://set of statements for case_constant2
  break;
 case case_constant3 ://set of statements for case_constant3
  break;
.
.
.
 default:
  //set of statements for default
}
flow of switch case in c

Example of switch case in c

#include <stdio.h>
int main(int argc, char const *argv[])
{
	char a='s';
	switch (a)
	{
		case 'a': 
		 printf("Case a");
		break;
		case 'b':
		 printf("Case b");
		break;
		case 'c':
		 printf("Case c");
		break;
		case 'd':
		 printf("Case d");
		break;
		case 's':
		 printf("Case s");
		break;
		default:
		 printf("No case is executed");
	}
	return 0;
}
switch case in c

Working of switch case

  • Expression specified in the switch statement is evaluated.
  • After evaluation the result is compared with the case constant values.
  • If there is a match for a case constant then the set of codes written for matched case constant is being executed. break; Is executed to stop the execution of rest of the case contant blocks.
  • If there is no match for case constants then default block is executed. If there is no default block written then simply control of execution exits from that switch case block.

What if there is no break statement for a case block?

Then all statements after the matching the case constant is being executed.

Is default mandatory?

Default block is not mandatory. default block is optional.


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What is switch case in c with example

Swtich case block in c programming language allows to execute a set of code among other sets of code.
Example:
#include <stdio.h>
int main(int argc, char const *argv[])
{
char a='s';
switch (a)
{
case 'a':
printf("Case a");
break;
case 'b':
printf("Case b");
break;
case 'c':
printf("Case c");
break;
case 'd':
printf("Case d");
break;
case 's':
printf("Case s");
break;
default:
printf("No case is executed");
}
return 0;
}

Output
switch case in c with example

Can we use char in switch case in c?

Yes you can use char in switch case in your c program as shown below.

#include <stdio.h>
int main(int argc, char const *argv[])
{
char a='s';
switch (a)
{
case 'a':
printf("Case a");
break;
case 'b':
printf("Case b");
break;
case 'c':
printf("Case c");
break;
case 'd':
printf("Case d");
break;
case 's':
printf("Case s");
break;
default:
printf("No case is executed");
}
return 0;
}

Output:
char in switch case in c

Why do we use switch case?

We use of switch case in c programming languagewith the help of switch case keywords when we can evaluate an expression to constant value and which can be mapped to its respected case block in multiway branching.

What is the difference between nested if and switch case statements?

If else statements or set of if statements evaluates the expression based on some range of values or some conditions. Switch case in c evaluates expression on the basis such that the result should be constant.
While compiling a c program compiler simply converts all if statements to its equivalent machine instructions because the condition variables may varie as those condition variables are not constant. In case of the switch case compiler inspects each case constants and creates a ” jump table” , “jump table is then used for selecting the path for execution of the c program.
Switch case in c is more efficient if there is a need such we have to select in large group of values. If else is not efficient it simply executes all if else blocks one after another.
If else is better for expressions which evaluates boolean values. Switch case is better for fixed constant values.
Switch case is faster than if else statements if there are good number of case blocks. If else block is slower than switch case when there is large number of if else statements.
If else statements may result is bad program behaviour if any of the if else block is missed. Switch case statements does not create problem it executes the default block.
Switch case statements are more readeble when compared to if else blocks.

Is switch case replacement of nested if else?

switch case in c is not replacement of nested if else.
If else statement executes each if else blocks until the specific condition is met, in case of switch case expression is being evaluated to a constant value then compiler inspects each case blocks and creates a jump table, according to the result constant respective jump is carried out.

Why switch case construct works faster than if-else construct?

We have already seen the working of switch case in c. Switch case in c first evaulates the expression which should result in a constant value. Then switch case inspects each and every case blocks and creates a jump table. During execution it simply executes the matched case constant from jump table.
In case of if else constuct compilers dont have the option to create jump table because the expression specified is a conditions. It has to evaluate each and every expression if else statements.
Hence we can see that switch case construct is faster if there is a need that it has to choose from large group of case constants.
If else construct is faster for boolean values.

Which one is better if else or switch case?

Both constructs have different implementations.
Depending on the need we can choose which one is better.
Switch case is better if there is a need that it has to choose from large group of case constants.
If else is better if we have to evaluate an expression which results in is a variable.


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