C Programming

Learning Objectives

After studying this topic, you will be able to:

• Understand the multiple if statement.
• Understand the if…else statement.
• Use relational and logical operators in conditions.
• Write simple C programs using decision-making statements.
• Develop algorithms and flowcharts for simple problems.

1. Multiple If Statement

Syntax

if (condition1)
{
    // statements
}

if (condition2)
{
    // statements
}

if (condition3)
{
    // statements
}

Important Point

In multiple if statements, every condition is checked independently. Therefore, more than one if block can execute if multiple conditions are true.

2. Example: Positive, Negative or Zero

The following program checks whether the entered number is positive, negative, or equal to zero.

#include <stdio.h>

int main()
{
    int a;

    printf("Enter any number: ");
    scanf("%d", &a);

    if (a == 0)
    {
        printf("Your number is Zero");
    }

    if (a > 0)
    {
        printf("%d is positive", a);
    }

    if (a < 0)
    {
        printf("%d is negative", a);
    }

    printf("\nThe End");

    return 0;
}

Example Output

3. Exercise: Display Number in Words

Write an algorithm, draw a flowchart, and write a C program to accept any one number from 2, 4, 6, or 8 and display its corresponding word.

Algorithm

1. Start.
2. Declare an integer variable n.
3. Accept a number from the user.
4. If n == 2, display TWO.
5. If n == 4, display FOUR.
6. If n == 6, display SIX.
7. If n == 8, display EIGHT.
8. If the number is not 2, 4, 6, or 8, display Invalid Input.
9. Stop.

Flowchart

C Program

#include <stdio.h>

int main()
{
    int n;

    printf("Enter any number 2, 4, 6 or 8 only: ");
    scanf("%d", &n);

    if (n == 2)
    {
        printf("TWO");
    }

    if (n == 4)
    {
        printf("FOUR");
    }

    if (n == 6)
    {
        printf("SIX");
    }

    if (n == 8)
    {
        printf("EIGHT");
    }

    if (n != 2 && n != 4 && n != 6 && n != 8)
    {
        printf("Invalid Input");
    }

    printf("\nThank You");

    return 0;
}

Example

4. if…else Statement

Syntax

if (condition)
{
    // statements executed when condition is true
}
else
{
    // statements executed when condition is false
}

5. Example: Find Greater Number

This program accepts two numbers and displays the greater number using if...else.

#include <stdio.h>

int main()
{
    int a, b;

    printf("Enter any two numbers: ");
    scanf("%d%d", &a, &b);

    if (a > b)
    {
        printf("%d is greater than %d", a, b);
    }
    else
    {
        printf("%d is greater than %d", b, a);
    }

    printf("\nThe End");

    return 0;
}

Example Output

6. Multiple If vs if…else

7. Operators Used in These Programs

8. Practice Questions

#include <stdio.h>

int main()
{
    float len, bre;

    printf("Enter length and breadth: ");
    scanf("%f%f", &len, &bre);

    if (len == bre)
    {
        printf("The shape is a Square");
    }
    else
    {
        printf("The shape is a Rectangle");
    }

    return 0;
}

#include <stdio.h>

int main()
{
    int n;

    printf("Enter a number: ");
    scanf("%d", &n);

    if (n % 2 == 0)
    {
        printf("%d is Even", n);
    }
    else
    {
        printf("%d is Odd", n);
    }

    return 0;
}

#include <stdio.h>

int main()
{
    int a, b;

    printf("Enter two numbers: ");
    scanf("%d%d", &a, &b);

    if (a > b)
    {
        printf("%d is the bigger number", a);
    }
    else if (b > a)
    {
        printf("%d is the bigger number", b);
    }
    else
    {
        printf("Both numbers are equal");
    }

    return 0;
}

#include <stdio.h>

int main()
{
    int x;

    printf("Enter a number: ");
    scanf("%d", &x);

    if (x >= 0)
    {
        printf("The number is greater than or equal to zero");
    }
    else
    {
        printf("The number is less than zero");
    }

    return 0;
}

#include <stdio.h>

int main()
{
    float amount;

    printf("Enter purchase amount: ");
    scanf("%f", &amount);

    if (amount > 5000)
    {
        printf("Discount Applicable");
    }
    else
    {
        printf("No Discount");
    }

    return 0;
}

#include <stdio.h>

int main()
{
    float price, finalPrice;

    printf("Enter actual price: ");
    scanf("%f", &price);

    if (price > 5000)
    {
        finalPrice = price - 50;
    }
    else
    {
        finalPrice = price;
    }

    printf("Final Price = Rs. %.2f", finalPrice);

    return 0;
}

#include <stdio.h>

int main()
{
    char ch;

    printf("Enter an alphabet: ");
    scanf(" %c", &ch);

    if (ch >= 'A' && ch <= 'Z')
    {
        printf("%c is an Uppercase alphabet", ch);
    }
    else if (ch >= 'a' && ch <= 'z')
    {
        printf("%c is a Lowercase alphabet", ch);
    }
    else
    {
        printf("Invalid input. Please enter an alphabet.");
    }

    return 0;
}

9. Additional Practice Questions

1. Write a C program to check whether a person’s age is eligible to vote.
2. Write a C program to check whether a number is divisible by 5.
3. Write a C program to check whether a student has passed or failed. Assume the passing mark is 35.
4. Write a C program to check whether a given character is a vowel or consonant.
5. Write a C program to check whether a number is positive or negative.
6. Write a C program to check whether a person is eligible for a senior citizen discount if their age is 60 or above.
7. Write a C program to check whether the entered number is divisible by both 3 and 5.
8. Write a C program to compare two numbers and display whether the first number is greater than, less than, or equal to the second number.

10. Quick Revision

• Multiple if: Used to check several independent conditions.
• if…else: Used when there are two possible outcomes.
• == checks equality.
• != checks inequality.
• > checks greater than.
• < checks less than.
• >= checks greater than or equal to.
• && means logical AND.
• % gives the remainder and is commonly used to check even/odd numbers.