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# if - else statement in C / C++ with example

In this tutorial, we will learn about `if - else` statement in C / C++ with examples. These are top examples of how to use `if - else` statement in C / C++. If you are learning about the `if - else` statement, it is impossible to ignore it.

First, you need to learn about `if - else` statement in C/C++. These are the basics to use in the examples.

## Top 10 if - else statement in C / C++ with examples

Here, we will give 10 examples of `if - else` statement in C / C++. These examples are written in two different languages, C and C++.

### Example 1: Finding the largest of three numbers with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int a, b, c, max;
cout << "Enter number a = ";
cin >> a;
cout << "Enter number b = ";
cin >> b;
cout << "Enter number c = ";
cin >> c;
max = a;
if(max < b) {
max = b;
}
if(max < c) {
max=c;
}
cout << "The largest of the three numbers " << a << ", " << b << ", " << c << " is: " << max;

cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>

int main(void) {
int a, b, c, max;
printf("Enter number a = ");
scanf("%d", &a);
printf("Enter number b = ");
scanf("%d", &b);
printf("Enter number c = ");
scanf("%d", &c);
max = a;
if(max < b) {
max = b;
}
if(max < c) {
max=c;
}
printf("The largest of the three numbers %d, %d, %d is: %d",a,b,c,max);

printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 2: Finding the smallest of three numbers with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int a, b, c, min;
cout << "Enter number a = ";
cin >> a;
cout << "Enter number b = ";
cin >> b;
cout << "Enter number c = ";
cin >> c;
min = a;
if(min > b) {
min = b;
}
if(min > c) {
min=c;
}
cout << "The smallest of the three numbers " << a << ", " << b << ", " << c << " is: " << min;

cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>

int main(void) {
int a, b, c, min;
printf("Enter number a = ");
scanf("%d", &a);
printf("Enter number b = ");
scanf("%d", &b);
printf("Enter number c = ");
scanf("%d", &c);
min = a;
if(min > b) {
min = b;
}
if(min > c) {
min = c;
}
printf("The smallest of the three numbers %d, %d, %d is: %d",a,b,c,min);

printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 3: Checking Even or Odd number with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int a;
cout<<"Enter number a = ";
cin>>a;

if(a % 2 == 0)
cout<<"\n"<<a<<" is the Even number.";
else
cout<<"\n"<<a<<" is the Odd number.";

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>

int main(void) {
int a;
printf("Enter number a = ");
scanf("%d", &a);

if(a % 2 == 0)
printf("\n%d is the Even number.", a);
else
printf("\n%d is the Odd number.", a);

printf("\n\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 4: Checking for Negative or Positive numbers with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int a;
cout<<"Enter number a = ";
cin>>a;

if(a > 0)
cout<<"\n"<<a<<" is the Positive numbers.";
else if(a < 0)
cout<<"\n"<<a<<" is the Negative number.";
else
cout<<"\nThis is zero.";

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>

int main(void) {
int a;
printf("Enter number a = ");
scanf("%d", &a);

if(a > 0)
printf("\n%d is the Positive numbers.", a);
else if(a < 0)
printf("\n%d is the Negative number.", a);
else
printf("\nThis is zero.");

printf("\n\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 5: Checking for Primes with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

bool isPrimes(int n)
{
if (n < 2){
return false;
}
if (n == 2){
return true;
}
if (n % 2 == 0){
return false;
}
for (int i = 3; i < (n - 1); i += 2){
if (n % i == 0){
return false;
}
}
return true;
}

int main() {
int a;
cout<<"Enter number a: ";
cin>>a;
if(isPrimes(a))
cout<<endl<<a<<" is the Primes.";
else
cout<<endl<<a<<" is not the Primes.";

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>
bool isPrimes(int n)
{
if (n < 2){
return false;
}
if (n == 2){
return true;
}
if (n % 2 == 0){
return false;
}
for (int i = 3; i < (n - 1); i += 2){
if (n % i == 0){
return false;
}
}
return true;
}

int main(void) {
int a;
printf("Enter number a: ");
scanf("%d", &a);
if(isPrimes(a))
printf("\n%d is the Primes.",a);
else
printf("\n%d is not the Primes.",a);

printf("\n\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 6: Checking for Perfect Squares with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

bool isPerfectSquares(int n){
int i = 0;
while(i*i <= n){
if(i*i == n){
return true;
}
++i;
}
return false;
}

int main() {
int a;
cout<<"Enter number a: ";
cin>>a;
if(isPerfectSquares(a))
cout<<endl<<a<<" is the Perfect Squares number.";
else
cout<<endl<<a<<" is not the Perfect Squares number.";

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>
bool isPerfectSquares(int n){
int i = 0;
while(i*i <= n){
if(i*i == n){
return true;
}
++i;
}
return false;
}

int main(void) {
int a;
printf("Enter number a: ");
scanf("%d", &a);
if(isPerfectSquares(a))
printf("\n%d is the Perfect Squares number.",a);
else
printf("\n%d is not the Perfect Squares number.",a);

printf("\n\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 7: Checking for Perfect number with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

bool isPerfectNumber(int a){
int sum = 0;
for(int i=1;i<=a/2;i++){
if(a%i==0)
sum+=i;
}
if(sum==a) return true;
return false;
}

int main() {
int a;
cout<<"Enter number a: ";
cin>>a;
if(isPerfectNumber(a))
cout<<endl<<a<<" is the Perfect number.";
else
cout<<endl<<a<<" is not the Perfect number.";

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>
bool isPerfectNumber(int a){
int sum = 0;
for(int i=1;i<=a/2;i++){
if(a%i==0)
sum+=i;
}
if(sum==a) return true;
return false;
}

int main(void) {
int a;
printf("Enter number a: ");
scanf("%d", &a);
if(isPerfectNumber(a))
printf("\n%d is the Perfect number.",a);
else
printf("\n%d is not the Perfect number.",a);

printf("\n\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 8: Displaying Even numbers in array with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int arr[]={1, 5, 9, 7, 11, 2, 10, 6, 7};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
cout<<"Elements of array: ";
while(i<9){
cout<<arr[i]<<" ";
i++;
}
cout<<"\nEven numbers in array: ";
while(j<9){
if(arr[j] % 2 == 0)
cout<<arr[j]<<" ";
j++;
}

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>

int main(void) {
int arr[]={1, 5, 9, 7, 11, 2, 10, 6, 7};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
printf("Elements of array: ");
while(i<9){
printf("%d ",arr[i]);
i++;
}
printf("\nEven numbers in array: ");
while(j<9){
if(arr[j] % 2 == 0)
printf("%d ",arr[j]);
j++;
}

printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 9: Displaying Odd numbers in array with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

int main() {
int arr[]={1, 5, 9, 7, 11, 2, 10, 6, 7};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
cout<<"Elements of array: ";
while(i<9){
cout<<arr[i]<<" ";
i++;
}
cout<<"\nOdd numbers in array: ";
while(j<9){
if(arr[j] % 2 == 1)
cout<<arr[j]<<" ";
j++;
}

cout<<"\n\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>

int main(void) {
int arr[]={1, 5, 9, 7, 11, 2, 10, 6, 7};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
printf("Elements of array: ");
while(i<9){
printf("%d ",arr[i]);
i++;
}
printf("\nOdd numbers in array: ");
while(j<9){
if(arr[j] % 2 == 1)
printf("%d ",arr[j]);
j++;
}

printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output:

### Example 10: Displaying Primes in array with if - else statement in C / C++

C++ programming:

```#include <iostream>
using namespace std;

bool isPrimes(int n)
{
if (n < 2){
return false;
}
if (n == 2){
return true;
}
if (n % 2 == 0){
return false;
}
for (int i = 3; i < (n - 1); i += 2){
if (n % i == 0){
return false;
}
}
return true;
}

int main() {
int arr[]={1, 5, 9, 7, 11};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
cout<<"Elements of array: ";
while(i<5){
cout<<arr[i]<<" ";
i++;
}
cout<<"\nPrimes in array: ";
while(j<5){
if(isPrimes(arr[j]))
cout<<arr[j]<<" ";
j++;
}

cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}```

C programming:

```#include <stdio.h>
#include <stdbool.h>

bool isPrimes(int n)
{
if (n < 2){
return false;
}
if (n == 2){
return true;
}
if (n % 2 == 0){
return false;
}
for (int i = 3; i < (n - 1); i += 2){
if (n % i == 0){
return false;
}
}
return true;
}

int main(void) {
int arr[]={1, 5, 9, 7, 11};
int i = 0, j = 0;
/* We have set the value of variable i
* to 0 as the array index starts with 0
* which means the first element of array
* starts with zero index.
*/
printf("Elements of array: ");
while(i<5){
printf("%d ",arr[i]);
i++;
}
printf("\nPrimes in array: ");
while(j<5){
if(isPrimes(arr[j]))
printf("%d ",arr[j]);
j++;
}

printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}```

Output: