C Language Examples - Code Killa

Basic Input & Output Examples

Learn Basic Input and Output in C programming with CodeKilla. Understand how to use printf() and scanf() for taking user input and displaying output effectively in C.

01. Hello World Program in C

#include <stdio.h>
int main(void) {
printf("Hello, World!\n");
return 0;
}

02. C Program to Print Your Name

#include<stdio.h>
int main(void) {
char name[100];
printf("Enter your name: ");
if (fgets(name, sizeof(name), stdin)) {
// remove trailing newline if present
size_t i = 0; while (name[i] != '\0') { if (name[i] == '\n') { name[i] = '\0'; break; } i++; }
printf("Hello, %s!\n", name);
}
return 0;
}

03. C Program to Add Two Numbers (User Input)

#include <stdio.h>
int main(void){
int num1,num2,sum;
// Prompt the user to enter two integers
printf("Enter two integers separated by space: ");
// Take input from the user
scanf("%d %d",&num1,&num2);
// Calculate the sum
sum=num1+num2;
// Display the result
printf("Sum=%d\n",sum);
return 0;
}

04. C Program to Add Two Numbers (User Input + Validation)

#include <stdio.h>
int main(void){
    int num1,num2;
    printf("Enter two integers separated by space: ");
    if(scanf("%d %d",&num1,&num2)==2){
        int sum=num1+num2;
        printf("Sum=%d\n",sum);
    }else{
        printf("Invalid input. Please enter two integers.\n");
    }
    return 0;
}

05. C Program to Substraction Two Numbers (User Input + Validation)

#include <stdio.h>
int main(void){
int num1,num2;
// Prompt the user to enter two integers
printf("Enter two integers separated by space: ");
// Validate input
if(scanf("%d %d",&num1,&num2)==2){
// Calculate the difference
int diff=num1-num2;
// Display the result
printf("Difference=%d\n",diff);
}else{
// Invalid input message
printf("Invalid input. Please enter two integers.\n");
}
return 0;
}

06. C Program to Swap Two Numbers Using Temp (or using a third variable)

#include <stdio.h>
int main(void) {
    int x, y, temp;
    printf("Enter two integers to swap: ");
    if (scanf("%d %d", &x, &y) == 2) {
        printf("Before swap: x = %d, y = %d\n", x, y);
        temp = x;
        x = y;
        y = temp;
        printf("After swap: x = %d, y = %d\n", x, y);
    }
    return 0;
}

07. C Program to Swap Two Numbers Using Without Using Temp (or without using a third variable)

#include <stdio.h>
int main(void) {
int x, y;
printf("Enter two integers to swap (without temp): ");
if (scanf("%d %d", &x, &y) == 2) {
printf("Before swap: x = %d, y = %d\n", x, y);
x = x + y;
y = x - y;
x = x - y;
printf("After swap: x = %d, y = %d\n", x, y);
}
return 0;
}

08. C Program to Find ASCII value of a character

#include <stdio.h>
int main(void) {
char ch;
printf("Enter a character: ");
// skip whitespace
if (scanf(" %c", &ch) == 1) {
printf("Character: %c, ASCII value: %d\n", ch, (int)ch);
}
return 0;
}

09. C Program to Multiply two floating numbers

#include <stdio.h>
int main(void) {
double a, b;
printf("Enter two floating-point numbers: ");
if (scanf("%lf %lf", &a, &b) == 2) {
printf("Product = %g\n", a * b);
}
return 0;
}

10. C Program to Find quotient and remainder

#include <stdio.h>
int main(void) {
int dividend, divisor;
printf("Enter dividend and divisor: ");
if (scanf("%d %d", &dividend, &divisor) == 2) {
if (divisor == 0) {
printf("Error: Division by zero.\n");
} else {
printf("Quotient = %d, Remainder = %d\n", dividend / divisor, dividend % divisor);
}
}
return 0;
}

11. C Program to Size of data types using sizeof()

#include <stdio.h>
int main(void) {
printf("Size of char: %zu byte(s)\n", sizeof(char));
printf("Size of int: %zu byte(s)\n", sizeof(int));
printf("Size of short: %zu byte(s)\n", sizeof(short));
printf("Size of long: %zu byte(s)\n", sizeof(long));
printf("Size of long long: %zu byte(s)\n", sizeof(long long));
printf("Size of float: %zu byte(s)\n", sizeof(float));
printf("Size of double: %zu byte(s)\n", sizeof(double));
return 0;
}

12. C Program to Convert Celsius to Fahrenheit

#include <stdio.h>
int main(void) {
double celsius;
printf("Enter temperature in Celsius: ");
if (scanf("%lf", &celsius) == 1) {
double fahrenheit = (celsius * 9.0 / 5.0) + 32.0;
printf("%.2f C = %.2f F\n", celsius, fahrenheit);
}
return 0;
}

13. C Program to Calculate the Area of a Circle

#include <stdio.h> // Include standard input-output header
#define PI 3.14159 // Define constant value for PI
int main(void){
float radius,area; // Declare variables
printf("Enter the radius of the circle:"); // Ask user for radius
scanf("%f",&radius); // Read input value
area=PI*radius*radius; // Calculate area using formula πr²
printf("Area of the circle=%.2f\n",area); // Display the result
return 0; // End of program
}

14. C Program to Calculate the Area of a Rectangle

#include <stdio.h> // Include standard input-output header
int main(void){
float length,width,area; // Declare variables
printf("Enter length and width of the rectangle:"); // Ask user for input
scanf("%f%f",&length,&width); // Read length and width
area=length*width; // Calculate area using formula length × width
printf("Area of the rectangle=%.2f\n",area); // Display the result
return 0; // End of program
}

15. C Program to Calculate Simple Interest

#include <stdio.h>
int main(void){
    float p,r,t,si; // p=Principal, r=Rate, t=Time, si=Simple Interest
    printf("Enter Principal, Rate, and Time: ");
    scanf("%f%f%f",&p,&r,&t); // input values
    si=(p*r*t)/100; // formula to calculate simple interest
    printf("Simple Interest = %.2f\n",si); // display result
    return 0;
}

C Conditional Statement Examples

Conditional statements in C help control program flow by making decisions based on conditions. Using if, else if, else, and nested if-else, programs execute different code blocks depending on whether conditions are true or false.

16. C Program to Check Even or Odd

#include <stdio.h>
int main(void){
    int n;
    printf("Enter number: ");
    scanf("%d",&n);
    if(n%2==0){
        printf("Even\n");
    }else{
        printf("Odd\n");
    }
    return 0;
}

17. C Program to Check Positive, Negative or Zero

#include <stdio.h>
int main(void){
    int n;
    printf("Enter number: ");
    scanf("%d",&n);
    if(n>0){
        printf("Positive\n");
    }else if(n<0){
        printf("Negative\n");
    }else{
        printf("Zero\n");
    }
    return 0;
}

18. C Program to Find Largest of Two Numbers

#include <stdio.h>
int main(void){
    int a,b;
    printf("Enter two numbers: ");
    scanf("%d%d",&a,&b);
    if(a>b){
        printf("%d is larger\n",a);
    }else if(b>a){
        printf("%d is larger\n",b);
    }else{
        printf("Both are equal\n");
    }
    return 0;
}

19. C Program to Find Largest of Three Numbers

#include <stdio.h>
int main(void){
    int a,b,c;
    printf("Enter three numbers: ");
    scanf("%d%d%d",&a,&b,&c);
    if(a>=b && a>=c){
        printf("%d is largest\n",a);
    }else if(b>=a && b>=c){
        printf("%d is largest\n",b);
    }else{
        printf("%d is largest\n",c);
    }
    return 0;
}

20. C Program to Check Divisible by 5 and 11

#include <stdio.h>
int main(void){
    int n;
    printf("Enter number: ");
    scanf("%d",&n);
    if(n%5==0 && n%11==0){
        printf("Divisible by 5 and 11\n");
    }else{
        printf("Not divisible by both\n");
    }
    return 0;
}

21. C Program to Check Profit or Loss Calculation

#include <stdio.h>
int main(void){
    float cp,sp;
    printf("Enter cost and selling price: ");
    scanf("%f%f",&cp,&sp);
    if(sp>cp){
        printf("Profit: %.2f\n",sp-cp);
    }else if(cp>sp){
        printf("Loss: %.2f\n",cp-sp);
    }else{
        printf("No profit no loss\n");
    }
    return 0;
}

22. C Program to Find Absolute Value

#include <stdio.h>
int main(void){
    int n;
    printf("Enter number: ");
    scanf("%d",&n);
    if(n<0){
        n=-n;
    }
    printf("Absolute value: %d\n",n);
    return 0;
}

23. C Program to Make Electricity Bill Calculator

#include <stdio.h>
int main(void){
    float units,bill;
    printf("Enter units: ");
    scanf("%f",&units);
    if(units<=100){
        bill=units*1.5;
    }else if(units<=200){
        bill=100*1.5+(units-100)*2;
    }else{
        bill=100*1.5+100*2+(units-200)*3;
    }
    printf("Bill = ₹%.2f\n",bill);
    return 0;
}

24. C Program to Check Given Character is a Vowel or Consonant

#include <stdio.h>
int main(void){
    char ch;
    printf("Enter letter: ");
    scanf(" %c",&ch);
    if(ch=='A'||ch=='E'||ch=='I'||ch=='O'||ch=='U'||ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u'){
        printf("Vowel\n");
    }else{
        printf("Consonant\n");
    }
    return 0;
}

25. C Program to Alphabet Check

#include <stdio.h>
int main(void){
    char ch;
    printf("Enter character: ");
    scanf(" %c",&ch);
    if((ch>='A' && ch<='Z')||(ch>='a' && ch<='z')){
        printf("Alphabet\n");
    }else{
        printf("Not alphabet\n");
    }
    return 0;
}

26. C Program to Check Uppercase or Lowercase

#include <stdio.h>
int main(void){
    char ch;
    printf("Enter character: ");
    scanf(" %c",&ch);
    if(ch>='A' && ch<='Z'){
        printf("Uppercase\n");
    }else if(ch>='a' && ch<='z'){
        printf("Lowercase\n");
    }else{
        printf("Not alphabet\n");
    }
    return 0;
}

27. C Program to Character Type Check

#include <stdio.h>
int main(void){
    char ch;
    printf("Enter character: ");
    scanf(" %c",&ch);
    if((ch>='A' && ch<='Z') || (ch>='a' && ch<='z')){
        printf("Alphabet\n");
    }else if(ch>='0' && ch<='9'){
        printf("Digit\n");
    }else{
        printf("Special character\n");
    }
    return 0;
}

28. C Program to Leap Year Check

#include <stdio.h>
int main(void){
    int y;
    printf("Enter year: ");
    scanf("%d",&y);
    if((y%4==0 && y%100!=0) || y%400==0){
        printf("Leap year\n");
    }else{
        printf("Not leap year\n");
    }
    return 0;
}

29. C Program to Print Student Grade from Marks

#include <stdio.h>
int main(void){
    int marks;
    printf("Enter marks: ");
    scanf("%d",&marks);
    if(marks>=90){
        printf("Grade A\n");
    }else if(marks>=75){
        printf("Grade B\n");
    }else if(marks>=60){
        printf("Grade C\n");
    }else if(marks>=40){
        printf("Grade D\n");
    }else{
        printf("Fail\n");
    }
    return 0;
}

30. C Program to Triangle Validity Check

#include <stdio.h>
int main(void){
    int a,b,c;
    printf("Enter 3 sides: ");
    scanf("%d%d%d",&a,&b,&c);
    if(a+b>c && b+c>a && c+a>b){
        printf("Valid triangle\n");
    }else{
        printf("Invalid triangle\n");
    }
    return 0;
}

31. C Program to Print Roots of Quadratic Equation

#include <stdio.h>
#include <math.h>
int main(void){
    float a,b,c,d;
    printf("Enter a,b,c: ");
    scanf("%f%f%f",&a,&b,&c);
    d=b*b-4*a*c;
    if(d>0){
        printf("Two real roots: %.2f and %.2f\n",(-b+sqrt(d))/(2*a),(-b-sqrt(d))/(2*a));
    }else if(d==0){
        printf("One real root: %.2f\n",-b/(2*a));
    }else{
        printf("Imaginary roots\n");
    }
    return 0;
}

32. C Program to Print Day of Week (Using Number)

#include <stdio.h>
int main(void){
    int d;
    printf("Enter day number (1-7): ");
    scanf("%d",&d);
    if(d==1){
        printf("Monday\n");
    }else if(d==2){
        printf("Tuesday\n");
    }else if(d==3){
        printf("Wednesday\n");
    }else if(d==4){
        printf("Thursday\n");
    }else if(d==5){
        printf("Friday\n");
    }else if(d==6){
        printf("Saturday\n");
    }else if(d==7){
        printf("Sunday\n");
    }else{
        printf("Invalid\n");
    }
    return 0;
}

33. C Program to Print Temperature Category

#include <stdio.h>
int main(void){
    float t;
    printf("Enter temperature: ");
    scanf("%f",&t);
    if(t<0){
        printf("Freezing\n");
    }else if(t<=20){
        printf("Cold\n");
    }else if(t<=35){
        printf("Warm\n");
    }else{
        printf("Hot\n");
    }
    return 0;
}

34. C Program to Make Simple Calculator (If-Else)

#include <stdio.h>
int main(void){
    char op;
    float a,b;
    printf("Enter operator (+,-,*,/): ");
    scanf(" %c",&op);
    printf("Enter two numbers: ");
    scanf("%f%f",&a,&b);
    if(op=='+'){
        printf("Result = %.2f\n",a+b);
    }else if(op=='-'){
        printf("Result = %.2f\n",a-b);
    }else if(op=='*'){
        printf("Result = %.2f\n",a*b);
    }else if(op=='/'){
        printf("Result = %.2f\n",a/b);
    }else{
        printf("Invalid operator\n");
    }
    return 0;
}

35. C Program to Check Whether a Number is Even, Odd, Whole, or Natural

#include <stdio.h>
int main(void){
int num;
// Prompt the user for input
printf("Enter a number: ");
scanf("%d",&num);
// Check if number is whole (0 and above)
if(num>=0){
printf("It is a Whole number.\n");
// Check if number is natural (positive integers only)
if(num>0){
printf("It is also a Natural number.\n");
}
// Check even or odd
if(num%2==0){
printf("It is an Even number.\n");
}else{
printf("It is an Odd number.\n");
}
}else{
printf("It is neither a Whole number nor a Natural number.\n");
}
return 0;
}

C Loops Examples

loops are control structures that execute a set of statements repeatedly until a specified condition becomes false. They improve efficiency by eliminating code repetition and are essential for tasks like iteration, computation, and data processing. C supports for, while, and do-while loops, each suited for different use cases of iteration control.

36. C Program to Print 1 to N

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter N: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        printf("%d ",i);
    }
    return 0;
}

37. C Program to Print even Numbers up to N

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter N: ");
    scanf("%d",&n);
    for(i=2;i<=n;i+=2){
        printf("%d ",i);
    }
    return 0;
}

38. C Program to Print odd Numbers up to N

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter N: ");
    scanf("%d",&n);
    for(i=1;i<=n;i+=2){
        printf("%d ",i);
    }
    return 0;
}

39. C Program to Print Sum of first N Numbers

#include <stdio.h>
int main(void){
    int n,i,sum=0;
    printf("Enter N: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        sum+=i;
    }
    printf("Sum = %d\n",sum);
    return 0;
}

40. C Program to Print Factorial of a Number

#include <stdio.h>
int main(void){
    int n,i;
    long long fact=1;
    printf("Enter number: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        fact*=i;
    }
    printf("Factorial = %lld\n",fact);
    return 0;
}

41. C Program to Print Multiplication Table

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter number: ");
    scanf("%d",&n);
    for(i=1;i<=10;i++){
        printf("%d x %d = %d\n",n,i,n*i);
    }
    return 0;
}

42. C Program to Reverse a Number

#include <stdio.h>
int main(void){
    int n,rev=0,rem;
    printf("Enter number: ");
    scanf("%d",&n);
    while(n!=0){
        rem=n%10;
        rev=rev*10+rem;
        n/=10;
    }
    printf("Reverse = %d\n",rev);
    return 0;
}

43. C Program to Check Palindrome Number

#include <stdio.h>
int main(void){
    int n,rev=0,rem,temp;
    printf("Enter number: ");
    scanf("%d",&n);
    temp=n;
    while(n!=0){
        rem=n%10;
        rev=rev*10+rem;
        n/=10;
    }
    if(temp==rev){
        printf("Palindrome\n");
    }else{
        printf("Not palindrome\n");
    }
    return 0;
}

44. C Program to Check Armstrong Number

#include <stdio.h>
#include <math.h>
int main(void){
    int n,temp,digits=0,rem,sum=0;
    printf("Enter number: ");
    scanf("%d",&n);
    temp=n;
    while(temp!=0){
        digits++;
        temp/=10;
    }
    temp=n;
    while(temp!=0){
        rem=temp%10;
        sum+=pow(rem,digits);
        temp/=10;
    }
    if(sum==n){
        printf("Armstrong number\n");
    }else{
        printf("Not Armstrong\n");
    }
    return 0;
}

45. C Program to Count Digits in a Number

#include <stdio.h>
int main(void){
    int n,count=0;
    printf("Enter number: ");
    scanf("%d",&n);
    while(n!=0){
        n/=10;
        count++;
    }
    printf("Digits = %d\n",count);
    return 0;
}

46. C Program to Print Sum of Digits

#include <stdio.h>
int main(void){
    int n,sum=0;
    printf("Enter number: ");
    scanf("%d",&n);
    while(n!=0){
        sum+=n%10;
        n/=10;
    }
    printf("Sum = %d\n",sum);
    return 0;
}

47. C Program to Print Product of Digits

#include <stdio.h>
int main(void){
    int n,prod=1;
    printf("Enter number: ");
    scanf("%d",&n);
    while(n!=0){
        prod*=n%10;
        n/=10;
    }
    printf("Product = %d\n",prod);
    return 0;
}

48. C Program to Print Power using Loop

#include <stdio.h>
int main(void){
    int base,exp,i;
    long long power=1;
    printf("Enter base and exponent: ");
    scanf("%d%d",&base,&exp);
    for(i=1;i<=exp;i++){
        power*=base;
    }
    printf("Result = %lld\n",power);
    return 0;
}

49. C Program to Check Strong Number

#include <stdio.h>
int fact(int n){
    int i,f=1;
    for(i=1;i<=n;i++){
        f*=i;
    }
    return f;
}
int main(void){
    int n,temp,sum=0,rem;
    printf("Enter number: ");
    scanf("%d",&n);
    temp=n;
    while(n!=0){
        rem=n%10;
        sum+=fact(rem);
        n/=10;
    }
    if(sum==temp){
        printf("Strong number\n");
    }else{
        printf("Not Strong\n");
    }
    return 0;
}

50. C Program to Check Perfect Number

#include <stdio.h>
int main(void){
    int n,i,sum=0;
    printf("Enter number: ");
    scanf("%d",&n);
    for(i=1;i<n;i++){
        if(n%i==0){
            sum+=i;
        }
    }
    if(sum==n){
        printf("Perfect number\n");
    }else{
        printf("Not perfect\n");
    }
    return 0;
}

51. C Program to Print Fibonacci Series

#include <stdio.h>
int main(void){
    int n,a=0,b=1,c,i;
    printf("Enter terms: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        printf("%d ",a);
        c=a+b;
        a=b;
        b=c;
    }
    return 0;
}

52. C Program to Check Prime Number Check or Not

#include <stdio.h>
int main(void){
    int n,i,flag=0;
    printf("Enter number: ");
    scanf("%d",&n);
    if(n<=1){
        printf("Not prime\n");
        return 0;
    }
    for(i=2;i<=n/2;i++){
        if(n%i==0){
            flag=1;
            break;
        }
    }
    if(flag==0){
        printf("Prime\n");
    }else{
        printf("Not prime\n");
    }
    return 0;
}

53. C Program to Print Prime Numbers in a Range

#include <stdio.h>
int main(void){
    int i,j,n1,n2,flag;
    printf("Enter range: ");
    scanf("%d%d",&n1,&n2);
    for(i=n1;i<=n2;i++){
        if(i<2) continue;
        flag=0;
        for(j=2;j<=i/2;j++){
            if(i%j==0){
                flag=1;
                break;
            }
        }
        if(flag==0){
            printf("%d ",i);
        }
    }
    return 0;
}

54. C Program to Find LCM of Two Numbers

#include <stdio.h>
int main(void){
    int a,b,max;
    printf("Enter two numbers: ");
    scanf("%d%d",&a,&b);
    max=(a>b)?a:b;
    while(1){
        if(max%a==0 && max%b==0){
            printf("LCM = %d\n",max);
            break;
        }
        max++;
    }
    return 0;
}

55. C Program to Find GCD or HCF of Two Numbers

#include <stdio.h>
int main(void){
    int a,b;
    printf("Enter two numbers: ");
    scanf("%d%d",&a,&b);
    while(a!=b){
        if(a>b){
            a-=b;
        }else{
            b-=a;
        }
    }
    printf("GCD = %d\n",a);
    return 0;
}

56. C Program to Convert Decimal to Binary

#include <stdio.h>
int main(void){
    int n,b[32],i=0;
    printf("Enter decimal: ");
    scanf("%d",&n);
    while(n>0){
        b[i]=n%2;
        n/=2;
        i++;
    }
    printf("Binary = ");
    for(i=i-1;i>=0;i--){
        printf("%d",b[i]);
    }
    return 0;
}

57. C Program to Convert Binary to Decimal

#include <stdio.h>
int main(void){
    long bin;
    int dec=0,base=1,rem;
    printf("Enter binary: ");
    scanf("%ld",&bin);
    while(bin>0){
        rem=bin%10;
        dec+=rem*base;
        bin/=10;
        base*=2;
    }
    printf("Decimal = %d\n",dec);
    return 0;
}

58. C Program to Reverse Multiplication Table

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter number: ");
    scanf("%d",&n);
    for(i=10;i>=1;i--){
        printf("%d x %d = %d\n",n,i,n*i);
    }
    return 0;
}

59. C Program to Sum of Even and Odd Numbers Separately

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter number: ");
    scanf("%d",&n);
    for(i=10;i>=1;i--){
        printf("%d x %d = %d\n",n,i,n*i);
    }
    return 0;
}

60. C Program to Display Numbers Divisible by 3 and 5

#include <stdio.h>
int main(void){
    int n,i;
    printf("Enter N: ");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        if(i%3==0 && i%5==0){
            printf("%d ",i);
        }
    }
    return 0;
}

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