C Tutorial

Control Flow in C

Control flow statements in C allow us to control the flow of execution of a program. They determine which statements should be executed based on certain conditions. There are three primary types of control flow statements in C:

🔄 If-Else Statements

The if statement allows you to execute a block of code based on a condition. If the condition evaluates to true, the block of code will execute. The else statement allows you to execute an alternative block if the condition is false.

if (condition) {
    // Block of code executed if condition is true
} else {
    // Block of code executed if condition is false
}
  

Example:

#include 

int main() {
    int age = 20;
    if (age >= 18) {
        printf("You are eligible to vote.\n");
    } else {
        printf("You are not eligible to vote.\n");
    }
    return 0;
}
  

🔄 Switch Case Statements

The switch statement evaluates an expression and executes the corresponding case based on the value of the expression. If no cases match, the default case is executed (if present).

switch (expression) {
    case value1:
        // Block of code executed for value1
        break;
    case value2:
        // Block of code executed for value2
        break;
    default:
        // Block of code executed if no case matches
}
  

Example:

#include 

int main() {
    int day = 3;
    switch (day) {
        case 1:
            printf("Monday\n");
            break;
        case 2:
            printf("Tuesday\n");
            break;
        case 3:
            printf("Wednesday\n");
            break;
        default:
            printf("Invalid day\n");
    }
    return 0;
}
  

🔄 Loops (for, while, do-while)

Loops allow you to repeat a block of code multiple times. There are three main types of loops in C:

• For Loop: Best when you know how many times you need to repeat the code.
• While Loop: Best when you don’t know how many times you need to repeat the code, but you have a condition to check.
• Do-While Loop: Similar to the while loop, but it executes the code block at least once, even if the condition is false.

For Loop Example:

#include 

int main() {
    for (int i = 1; i <= 5; i++) {
        printf("%d\n", i);
    }
    return 0;
}
  

While Loop Example:

#include 

int main() {
    int i = 1;
    while (i <= 5) {
        printf("%d\n", i);
        i++;
    }
    return 0;
}
  

Do-While Loop Example:

#include 

int main() {
    int i = 1;
    do {
        printf("%d\n", i);
        i++;
    } while (i <= 5);
    return 0;
}
  

📝 Try It Yourself

❌ Common Mistakes

• 🚫 Forgetting to update the loop counter in a loop, which leads to an infinite loop.
• 🚫 Using break and continue incorrectly inside loops.
• 🚫 Missing break statement in a switch case, causing the code to "fall through" to the next case.