Conditional Statements

Conditional statements execute specific code blocks based on whether a condition evaluates to true or false. They are crucial for branching logic, such as validating input, comparing values, or directing program flow.

1. if Statement

• Purpose: Executes a code block if a condition is true.
• Why Necessary: Enables simple checks, like verifying if a value meets a criterion before proceeding.
• Syntax:

if (condition) {
    // code to execute if condition is true
}

• Example: Check if a number is even.

#include <stdio.h>

int main() {
    int num = 4;
    if (num % 2 == 0) {
        printf("The number is even.\n");
    }
    return 0;
}

Output: The number is even.

2. if-else Statement

• Purpose: Executes one block if the condition is true, another if false.
• Why Necessary: Provides binary decision-making, such as pass/fail or yes/no scenarios.
• Syntax:

if (condition) {
    // code if true
} else {
    // code if false
}

• Example: Determine if a number is positive or negative.

#include <stdio.h>

int main() {
    int num = -5;
    if (num > 0) {
        printf("The number is positive.\n");
    } else {
        printf("The number is negative or zero.\n");
    }
    return 0;
}

Output: The number is negative or zero.

3. else-if Ladder

• Purpose: Checks multiple conditions sequentially, executing the first true condition’s block.
• Why Necessary: Handles scenarios with more than two outcomes, like grading systems or categorizing data.
• Syntax:

if (condition1) {
    // code if condition1 is true
} else if (condition2) {
    // code if condition2 is true
} else if (condition3) {
    // code if condition3 is true
} else {
    // code if all conditions are false
}

• Example: Assign a grade based on a score.

#include <stdio.h>

int main() {
    int score = 85;
    if (score >= 90) {
        printf("Grade: A\n");
    } else if (score >= 80) {
        printf("Grade: B\n");
    } else if (score >= 70) {
        printf("Grade: C\n");
    } else if (score >= 60) {
        printf("Grade: D\n");
    } else {
        printf("Grade: F\n");
    }
    return 0;
}

Output: Grade: B

4. Nested if-else

• Purpose: Places if-else statements inside another if or else block for layered conditions.
• Why Necessary: Supports complex decision-making, such as checking multiple criteria within a condition.
• Syntax:

if (condition1) {
    if (condition2) {
        // code if both conditions are true
    } else {
        // code if condition1 true, condition2 false
    }
} else {
    // code if condition1 is false
}

• Example: Check if a number is positive and even.

#include <stdio.h>

int main() {
    int num = 6;
    if (num > 0) {
        if (num % 2 == 0) {
            printf("The number is positive and even.\n");
        } else {
            printf("The number is positive but odd.\n");
        }
    } else {
        printf("The number is negative or zero.\n");
    }
    return 0;
}

Output: The number is positive and even.

5. switch Statement

• Purpose: Matches an expression against multiple case values to execute corresponding code.
• Why Necessary: Simplifies multi-way branching (e.g., menus or enums) compared to multiple if-else statements.
• Syntax:

switch (expression) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // code if no match
}

• Example: Simple calculator for operations.

#include <stdio.h>

int main() {
    char op = '+';
    int a = 10, b = 5;
    switch (op) {
        case '+':
            printf("Sum: %d\n", a + b);
            break;
        case '-':
            printf("Difference: %d\n", a - b);
            break;
        default:
            printf("Invalid operator.\n");
    }
    return 0;
}

Output: Sum: 15