Conditional Statements

In real life, we constantly make decisions.

For example:

If it is raining, take an umbrella. Otherwise, don't.

Programs also need to make decisions based on certain conditions. This is where conditional statements come in.

What are Conditional Statements?

Conditional statements allow a program to execute different blocks of code depending on whether a condition is true or false.

For example:

int age = 20;

if (age >= 18)
{
    printf("You are eligible to vote.");
}

Since age >= 18 is true, the message is displayed.

if Statement

The if statement executes a block of code only when a condition is true.

Syntax

if (condition)
{
    // code
}

Example

int marks = 80;

if (marks >= 40)
{
    printf("Pass");
}

Output:

Pass

If the condition is false, the code inside if is simply skipped.

if-else Statement

Sometimes we want to perform one action if the condition is true and another if it is false.

For this, we use if-else.

int marks = 35;

if (marks >= 40)
{
    printf("Pass");
}
else
{
    printf("Fail");
}

Output:

Fail

Think of it as:

       Condition
       /       \
    True       False
     ↓           ↓
   if          else

if-else if-else

When we have multiple conditions, we can use an else if ladder.

For example, let's assign grades based on marks:

int marks = 85;

if (marks >= 90)
{
    printf("A+");
}
else if (marks >= 80)
{
    printf("A");
}
else if (marks >= 70)
{
    printf("B");
}
else
{
    printf("C");
}

Output:

A

C checks the conditions from top to bottom and executes the first matching block.

Nested if

An if statement can also be placed inside another if statement. This is called a nested if.

int age = 20;
int hasID = 1;

if (age >= 18)
{
    if (hasID)
    {
        printf("Entry allowed");
    }
}

Here, the second condition is checked only if the first condition is true.

switch Statement

When we need to choose between multiple fixed values, switch can make the code cleaner.

For example:

int day = 2;

switch (day)
{
    case 1:
        printf("Monday");
        break;

    case 2:
        printf("Tuesday");
        break;

    case 3:
        printf("Wednesday");
        break;

    default:
        printf("Invalid day");
}

Output:

Tuesday

The break statement stops execution from continuing into the next case.

if-else vs switch

In Simple Words

Conditional statements allow a C program to make decisions.

The main conditional statements you'll use are:

• if

• if-else

• if-else if-else

• Nested if

• switch

For example, a program can check a student's marks and decide whether the student passed, failed, or received a particular grade.