8. Practical Examples

8.1 Complete Program Examples 
 Example 1: Simple Calculator 
 #include <stdio.h>

int main() {
 float num1, num2, result;
 char operator;
 
 printf("Enter first number: ");
 scanf("%f", &num1);
 
 printf("Enter operator (+, -, *, /): ");
 scanf(" %c", &operator);
 
 printf("Enter second number: ");
 scanf("%f", &num2);
 
 switch (operator) {
 case '+':
 result = num1 + num2;
 break;
 case '-':
 result = num1 - num2;
 break;
 case '*':
 result = num1 * num2;
 break;
 case '/':
 if (num2 != 0) {
 result = num1 / num2;
 } else {
 printf("Error: Division by zero!\n");
 return 1;
 }
 break;
 default:
 printf("Error: Invalid operator!\n");
 return 1;
 }
 
 printf("%.2f %c %.2f = %.2f\n", num1, operator, num2, result);
 return 0;
}
 
 Example 2: Grade Classification 
 #include <stdio.h>

int main() {
 int score;
 
 printf("Enter your score (0-100): ");
 scanf("%d", &score);
 
 if (score < 0 || score > 100) {
 printf("Invalid score!\n");
 } else if (score >= 90) {
 printf("Grade: A (Excellent)\n");
 } else if (score >= 80) {
 printf("Grade: B (Very Good)\n");
 } else if (score >= 70) {
 printf("Grade: C (Good)\n");
 } else if (score >= 60) {
 printf("Grade: D (Fair)\n");
 } else {
 printf("Grade: F (Fail)\n");
 }
 
 return 0;
}
 
 8.2 Loop Examples 
 Example 1: Sum of Numbers 
 #include <stdio.h>

int main() {
 int n, sum = 0;
 
 printf("Enter a positive integer: ");
 scanf("%d", &n);
 
 for (int i = 1; i <= n; i++) {
 sum += i;
 }
 
 printf("Sum of numbers from 1 to %d is: %d\n", n, sum);
 return 0;
}
 
 Example 2: Multiplication Table 
 #include <stdio.h>

int main() {
 int num;
 
 printf("Enter a number: ");
 scanf("%d", &num);
 
 printf("Multiplication table for %d:\n", num);
 for (int i = 1; i <= 10; i++) {
 printf("%d x %d = %d\n", num, i, num * i);
 }
 
 return 0;
}