Nested If-Else Statement in C 

Nested if-else statements in C Language:

When an if-else statement is present inside the body of another “if” or “else” then this is called nested if-else. Nested ‘if’ statements are used when we want to check for a condition only when a previous dependent condition is true or false. C allows us to nested if statements within if statements, i.e. we can place an if statement inside another if statement.

What is the Nested If block?

Nested if block means defining if block inside another if block. We can also define the if block inside the else blocks. Depending on our logic requirements, we can use nested if block in n number of ways. You can define nested if block at many levels. First, we will see the syntax and example, and later part of this article, we will understand the flowchart by taking one example.

Nested If-Else Statement Syntax in C Language:

lease have a look at the below image which shows the different ways to use the nested if block in C Programming Language.

Nested If-Else Statement Syntax in C Language

Now, we will take one example and try to understand the flow chart. We are taking the following syntax. Here, we have an if-else block inside the if block, as well as, an if-else block inside the else block.

Nested If-Else Statement in C Language with Examples
How Nested IF ELSE work in C Language?

First, it will check the first if condition i.e. the outer if condition and if it is true, then the outer else block will be terminated. So, the control moves inside the first or the outer if block. Then again it checks the inner if condition and if the inner if condition is true, then the inner else block gets terminated. So, in this case, the outer if and inner if block statements get executed.

Now, if the outer if condition is true, but the inner if condition is false, then the inner if block gets terminated. So, in this case, the outer if and inner else block statements get executed.

Now, if the outer if condition is false, then the outer if block gets terminated and control moves to the outer else block. And inside the outer else block, again it checks the inner if condition, and if the inner if condition is true, then the inner else block gets terminated. So, in this case, the outer else and inner if block statements get executed.

Now, if the outer if condition is false as well as the if condition inside the outer else blocks also failed, then the if block gets terminated. And in this case, the outer else and inner else block statements get executed. This is how statements get executed in Nested if. Now we will see the flow chart of nested if blocks.

Flow chart of Nested If Block in C Programming Language:

First, have a look at the below diagram which shows the flow chart of the nested if-else statement.

Flow chart of Nested If Block in C Programming Language

First, it will check the outer if condition, and if the outer if condition is true, then the control comes inside and it will check the inner if condition, and if the inner if condition is true, then the outer if block statements and inner if block statements get executed. And after execution, it will come to end.

Suppose, the outer if condition is true but the inner if condition is failed, then the outer if block statements and the inner else block statement get executed. And once the statement gets executed, it will come to end.

Suppose, the outer if condition is failed, then the control directly comes to the else block and checks the inner if condition. And again, for the inner if condition two options are there. If the inner if condition is true, then it will execute the outer else block and inner if block statement, and if the inner if condition is false, then it will execute the outer else block and inner else block statements and then comes to end.

Program to understand Nested IF-ELSE statements in C Language:
#include <stdio.h>
int main()
{
int i = 10;
if (i == 10)
{
   if (i < 15) // First if statement
    printf("i is smaller than 15\n"); // Nested - if statement
    // Will only be executed if statement above is true.
      if (i < 12)
         printf("i is smaller than 12 too\n");
      else
         printf("i is greater than 15");
}
return 0;
}
Output:
Program to understand nested if else statements in C
Ladder if-else statements in C Language:

In Ladder if-else statements one of the statements will be executed depending upon the truth or falsity of the conditions. if the condition1 is true then Statement 1 will be executed and so on but if all conditions are false then Statement 3 will be executed. The C if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the C else-if ladder is bypassed. If none of the conditions are true, then the final else statement will be executed.

Ladder if-else statements in C Language
Syntax to use Ladder if-else statements in C Language:
Syntax to use Ladder if-else statements in C Language
Program to understand Ladder if-else statements in C Language:
#include <stdio.h>
int main()
{
  int i = 20;
  if (i == 10)
  {
    printf("i is 10");
  }
  else if (i == 15)
  {
    printf("i is 15");
  }
  else if (i == 20)
  {
    printf("i is 20");
  }
  else
  {
    printf("i is not present");
  }
}

Output: i is 20

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