C Programming Language Free Course Part-2
Control Structures
Control structures are used to alter the flow of execution in a program based on certain conditions. These include conditional statements and loops.
1. if Statement
The if statement evaluates a condition. If the condition is true, the block of code inside the if statement is executed.
Example:
if (condition) {
// Code to execute if condition is true
}2. if-else" Statement
The if-else statement allows for two paths of execution. If the condition is true, the if block executes; otherwise, the else block executes.
Example:
if (condition) {
// Code to execute if condition is true
} else {
// Code to execute if condition is false
}3. if-else if Ladder
This is used when there are multiple conditions to evaluate. It checks each condition in sequence until it finds one that is true.
Example:
if (condition1) {
// Code to execute if condition1 is true
} else if (condition2) {
// Code to execute if condition2 is true
} else if (condition3) {
// Code to execute if condition3 is true
} else {
// Code to execute if none of the above conditions are true
}
4. Nesting of if
Nesting refers to placing one if statement inside another. This allows for more complex decision-making.
Example:
if (condition1) {
if (condition2) {
// Code to execute if both condition1 and condition2 are true
}
}
Loops
Loops allow a block of code to be executed repeatedly based on a condition. The main types of loops in C are for, while, and do-while.
1. for Loop
The for loop is used when the number of iterations is known. It has an initializer, a condition, and an increment/decrement.
Example:
for (initialization; condition; increment) {
// Code to execute repeatedly
}
Example:
for (int i = 0; i < 10; i++) {
printf("%d\n", i);
}
2. while Loop
The while loop repeats as long as the condition is true. The condition is checked before the loop body is executed.
while (condition) {
// Code to execute repeatedly
}
Example:
int i = 0;
while (i < 10) {
printf("%d\n", i);
i++;
}
3. do-while Loop
The do-while loop is similar to the while loop, but the condition is checked after the loop body is executed, ensuring that the loop body runs at least once.
Example:
do {
// Code to execute
} while (condition);
Example:
int i = 0;
do {
printf("%d\n", i);
i++;
} while (i < 10);
Jump Statements
Jump statements are used to alter the flow of control by jumping to another part of the program.
1. break
The break statement is used to exit a loop or switch statement prematurely.
Usage in Loops:
Example:
for (int i = 0; i < 10; i++) {
if (i == 5) {
break; // Exit the loop when i is 5
}
printf("%d\n", i);
}
Usage in Switch:
switch (expression) {
case 1:
// Code
break;
case 2:
// Code
break;
default:
// Default code
}
2. continue
The continue statement skips the current iteration of a loop and moves to the next iteration.
Example:
for (int i = 0; i < 10; i++) {
if (i % 2 == 0) {
continue; // Skip the rest of the loop body for even numbers
}
printf("%d\n", i);
}
3. goto
The goto statement allows you to jump to a labeled statement in the program. It is generally discouraged as it can make code harder to follow.
Example:
int i = 0;
start:
printf("%d\n", i);
i++;
if (i < 5) {
goto start;
}
4. exit
The exit function terminates program execution immediately. It is part of the standard library and requires including <stdlib.h>.
Example:
int main() {
printf("Program will exit now.\n");
exit(0); // Exits the program
}
Switch Statement
The switch statement is a multi-way branch statement that provides an efficient way to transfer control to different parts of code based on the value of an expression.
switch (expression) {
case constant1:
// Code for case 1
break;
case constant2:
// Code for case 2
break;
// More cases
default:
// Code if no case matches
}
Example:
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");
}
Types of Loops
Loops can be categorized based on how they are controlled:
- Entry-Controlled Loops: The condition is checked before the loop body is executed. (
forandwhileloops) - Exit-Controlled Loops: The loop body is executed at least once, and the condition is checked after the loop body. (
do-whileloop)
Example Programs
Example 1: Print Even Numbers
This program prints even numbers from 0 to 10 using a for loop.
int main() {
for (int i = 0; i <= 10; i++) {
if (i % 2 == 0) {
printf("%d\n", i);
}
}
return 0;
}
Example 2: Factorial Calculation
This program calculates the factorial of a number using a while loop.
int main() {
int n, factorial = 1;
printf("Enter a number: ");
scanf("%d", &n);
int i = 1;
while (i <= n) {
factorial *= i;
i++;
}
printf("Factorial of %d is %d\n", n, factorial);
return 0;
}
Example 3: Menu Selection Using Switch
This program demonstrates using a switch statement to implement a simple menu.
int main() {
int choice;
printf("Menu:\n");
printf("1. Add\n");
printf("2. Subtract\n");
printf("3. Multiply\n");
printf("4. Divide\n");
printf("Enter your choice: ");
scanf("%d", &choice); switch (choice) {
case 1:
printf("You selected Add\n");
break;
case 2:
printf("You selected Subtract\n");
break;
case 3:
printf("You selected Multiply\n");
break;
case 4:
printf("You selected Divide\n");
break;
default:
printf("Invalid choice\n");
}
return 0;
}
Understanding these control structures and loops is crucial for writing efficient and effective C programs. They provide the necessary tools to control the flow of a program and to repeat tasks, allowing for complex logic and operations.
