Decision control structure in C

A decision control structure in C is used to perform different actions based on different conditions. These structures allow the program to make decisions and execute specific blocks of code based on the evaluation of boolean expressions. The primary decision control structures in C include:

Understand the decision control structure in C

• if Statement
• if-else Statement
• nested if Statement
• if-else-if Ladder
• switch Statement

if Statement in C

The if statement evaluates a condition and executes a block of code only if the condition is true.

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

Example:

int x = 10;
if (x > 0) {
    printf("x is positive");
}

if-else Statement

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

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

Example:

int x = -10;
if (x > 0) {
    printf("x is positive");
} else {
    printf("x is negative or zero");
}

nested if Statement in C

A nested if statement is an if statement placed inside another if or else block. This allows multiple levels of condition checking.

if (condition1) {
    if (condition2) {
        // Code to be executed if both condition1 and condition2 are true
    }
}

Example:

int x = 10, y = 20;
if (x > 0) {
    if (y > 0) {
        printf("Both x and y are positive");
    }
}

if-else-if Ladder

The if-else-if ladder is used to test multiple conditions. It executes the block of code corresponding to the first true condition.

if (condition1) {
    // Code to be executed if condition1 is true
} else if (condition2) {
    // Code to be executed if condition2 is true
} else if (condition3) {
    // Code to be executed if condition3 is true
} else {
    // Code to be executed if all conditions are false
}

Example:

int x = 0;
if (x > 0) {
    printf("x is positive");
} else if (x < 0) {
    printf("x is negative");
} else {
    printf("x is zero");
}

switch Statement in C

The switch statement allows a variable to be tested for equality against a list of values, each with its own block of code.

switch (expression) {
    case constant1:
        // Code to be executed if expression equals constant1
        break;
    case constant2:
        // Code to be executed if expression equals constant2
        break;
    // More cases
    default:
        // Code to be executed if expression doesn't match any case
}

Example

int day = 3;
switch (day) {
    case 1:
        printf("Monday");
        break;
    case 2:
        printf("Tuesday");
        break;
    case 3:
        printf("Wednesday");
        break;
    case 4:
        printf("Thursday");
        break;
    case 5:
        printf("Friday");
        break;
    case 6:
        printf("Saturday");
        break;
    case 7:
        printf("Sunday");
        break;
    default:
        printf("Invalid day");
}

These decision control structures are fundamental to controlling the flow of a C program based on dynamic conditions.