C Programming - C Decision Making

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C Programming - C Decision Making

C Decision Making

In C programming, decision-making statements allow the program to execute different statements based on conditions. These statements evaluate an expression or condition and make decisions accordingly.

Types of Decision Making Statements in C

1. if statement
2. if-else statement
3. else-if ladder
4. switch statement
5. ternary operator (? :)

1. if Statement

The if statement evaluates a condition and, if the condition is true, executes the block of code inside the curly braces {}.

• Syntax:

if (condition) {
    // Code to be executed if condition is true
}

• Example:

int a = 10;
if (a > 5) {
    printf("a is greater than 5\n");
}
// Output: a is greater than 5

2. if-else Statement

The if-else statement evaluates a condition and executes one block of code if the condition is true and another block if the condition is false.

• Syntax:

if (condition) {
    // Code to be executed if condition is true
} else {
    // Code to be executed if condition is false
}

• Example:

int a = 3;
if (a > 5) {
    printf("a is greater than 5\n");
} else {
    printf("a is less than or equal to 5\n");
}
// Output: a is less than or equal to 5

3. else-if Ladder

The else-if ladder is used when you need to test multiple conditions. If the first condition is false, it checks the second condition, and so on.

• Syntax:

if (condition1) {
    // Code to be executed if condition1 is true
} else if (condition2) {
    // Code to be executed if condition2 is true
} else {
    // Code to be executed if all the above conditions are false
}

• Example:

int a = 10;
if (a > 15) {
    printf("a is greater than 15\n");
} else if (a > 5) {
    printf("a is greater than 5 but less than or equal to 15\n");
} else {
    printf("a is less than or equal to 5\n");
}
// Output: a is greater than 5 but less than or equal to 15

4. switch Statement

The switch statement is used to check a variable against a set of values. It is a cleaner alternative to a series of if-else if statements when you need to evaluate the same variable or expression.

• Syntax:

switch (expression) {
    case value1:
        // Code to be executed if expression == value1
        break;
    case value2:
        // Code to be executed if expression == value2
        break;
    default:
        // Code to be executed if none of the cases match
}

• Example:

int day = 3;
switch (day) {
    case 1:
        printf("Monday\n");
        break;
    case 2:
        printf("Tuesday\n");
        break;
    case 3:
        printf("Wednesday\n");
        break;
    case 4:
        printf("Thursday\n");
        break;
    case 5:
        printf("Friday\n");
        break;
    default:
        printf("Invalid day\n");
}
// Output: Wednesday

• Note :
• break is used to exit the switch block.
• The default case is optional but is used when no cases match.

5. Ternary Operator (? :)

The ternary operator is a shorthand for the if-else statement. It allows you to assign a value based on a condition in a concise way.

• Syntax:

condition ? expression_if_true : expression_if_false;

• Example:

int a = 10, b = 5;
int max = (a > b) ? a : b;  // If a > b, max gets the value of a, else b
printf("Max value: %d\n", max);  // Output: Max value: 10

Decision-Making Example:

#include <stdio.h>
 
int main() {
    int a = 10, b = 20, choice;
 
    printf("Enter your choice (1 for addition, 2 for subtraction): ");
    scanf("%d", &choice);
 
    if (choice == 1) {
        printf("Addition result: %d\n", a + b);
    } else if (choice == 2) {
        printf("Subtraction result: %d\n", a - b);
    } else {
        printf("Invalid choice\n");
    }

    return 0;
}

Output (example):

Enter your choice (1 for addition, 2 for subtraction): 1
Addition result: 30

Summary of Decision Making in C

1. if statement: Executes a block of code if a condition is true.
2. if-else statement: Executes one block of code if the condition is true, and another block if false.
3. else-if ladder: Allows testing multiple conditions sequentially.
4. switch statement: Selects one of many code blocks to execute based on the value of an expression.
5. Ternary operator (? :): A concise way to implement a simple if-else statement.

Decision-making statements are fundamental to controlling the flow of a program based on conditions in C. They enable the program to make choices and execute the relevant code accordingly.