Searching and sorting arrays in C / C++ How to use if - else statement in C / C++
In this tutorial, we will learn about if - else statement in C / C++ and its working with the help of some examples. This is one of the basic knowledge in C / C++ programming language, so please learn it carefully.
In C / C++ programming, if - else statement is used to execute a block of code in a certain condition. There are two cases:
- If condition is true: Execute block of code.
- If the condition is false: Skip the code block and execute the statements below.
For example: assigning grades (A, B, C) based on marks obtained by a student.
- If the percentage is above 90, assign grade A.
- If the percentage is above 75 and below 90, assign grade B.
- If the percentage is above 65 and below 75, assign grade C.
There are three forms of if - else statements in C / C++.
ifstatement in C / C++.if - elsestatement in C / C++.if - else else - ifstatement in C / C++.
Now, we will learn about each form of if - else statement in C / C++ one by one.
if statement in C / C++
The if statement in C / C++ is used in case we only have a single condition. That means, if the condition is true then do something and if the condition is false then skip.
The syntax of if statement in C / C++:
if (condition) {
// body of if statement
}Here,
- condition: This is the condition of the
ifstatement.- If the condition evaluates to true: The block of code inside the
ifstatement body is executed. - If the condition evaluates to false: The block of code inside the
ifstatement body is skipped.
- If the condition evaluates to true: The block of code inside the
*Note: Condition is placed inside ( ) and code block is placed inside { }.
For example: Check positive with if statement in C / C++.
C++ programming:
/* Program to print positive number entered by the user
If the user enters a negative number, it is skipped */
#include <iostream>
using namespace std;
int main() {
int number;
cout << "Enter an integer: ";
cin >> number;
// checks if the number is positive
if (number > 0) {
cout << "You entered a positive integer: " << number << endl;
}
cout << "This statement is always executed.";
cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}C programming:
#include <stdio.h>
int main(void) {
int number;
printf("Enter an integer: ");
scanf("%d", &number);
// checks if the number is positive
if (number > 0) {
printf("You entered a positive integer: %d\n",number);
}
printf("This statement is always executed.");
printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}Output:
if - else statement in C / C++
The if - else statement is used in case of multiple conditions. Each condition will execute a different block of code.
The syntax of if - else statement in C / C++:
if (condition) {
// block of code if condition is true
}
else {
// block of code if condition is false
}Explain:
- If the condition evaluates true:
- The code inside the body of the
ifis executed. - The code inside the body of the
elseis skipped from execution.
- The code inside the body of the
- if the condistion evaluates false:
- The code inside the body of the
elseis executed. - The code inside the body of the
ifis skipped from execution.
- The code inside the body of the
For example: Check even or odd number with if - else statement in C / C++.
C++ programming:
#include <iostream>
using namespace std;
int main() {
int number;
cout << "Enter an integer: ";
cin >> number;
if (number % 2 == 0) {
cout << "You entered a even number: " << number << endl;
}
else{
cout << "You entered a odd number: " << number << endl;
}
cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}C programming:
#include <stdio.h>
int main(void) {
int number;
printf("Enter an integer: ");
scanf("%d", &number);
if (number % 2 == 0) {
printf("You entered a even number: %d\n",number);
}
else{
printf("You entered a odd number: %d\n",number);
}
printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}Output:
if - else else - if statement in C / C++
The if - else else if statement is used in case there are more than two alternatives.
The syntax of if - else else - if statement in C / C++:
if (condition1) {
// code block 1
}
else if (condition2){
// code block 2
}
else {
// code block 3
}Explain:
- If the
condition1 is true: Theblock code 1is executed. - if the
condition 1is false: Theblock code 1is skipped and thecondition 2is evaluated.- If the
condition 2is true: Theblock code 2is excuted. - If the
condition 2is false: Theblock code 3is executed.
- If the
For example: Program to check whether an integer is positive, negative or zero.
C++ programming:
#include <iostream>
using namespace std;
int main() {
int number;
cout << "Enter an integer: ";
cin >> number;
if (number > 0) {
cout << "You entered a positive integer: " << number << endl;
}
else if (number < 0) {
cout << "You entered a negative integer: " << number << endl;
}
else {
cout << "You entered 0." << endl;
}
cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}C programming:
#include <stdio.h>
int main(void) {
int number;
printf("Enter an integer: ");
scanf("%d", &number);
if (number > 0) {
printf("You entered a positive integer: %d\n",number);
}
else if (number < 0) {
printf("You entered a negative integer: %d\n",number);
}
else {
printf("You entered 0.\n");
}
printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}Output 1:
Output 2:
Output 3:
Nestef if statement in C / C++
The nested if statement occurs where one if statement is inside another if statement.
Think of it as a multi-class if statement. The outer class is an if statement and its inner class adds one more if statement.
The syntax of nested if statement in C / C++:
// outer if statement
if (condition1) {
// statements
// inner if statement
if (condition2) {
// statements
}
}For example: Program to check whether an integer is positive, negative or zero using nested if statement in C / C++.
C++ programming:
#include <iostream>
using namespace std;
int main() {
int number;
cout << "Enter an integer: ";
cin >> number;
if(number != 0){
if (number > 0) {
cout << "You entered a positive integer: " << number << endl;
}
else if (number < 0) {
cout << "You entered a negative integer: " << number << endl;
}
}
else {
cout << "The number is 0 and it is neither positive nor negative." << endl;
}
cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}C programming:
#include <stdio.h>
int main(void) {
int number;
printf("Enter an integer: ");
scanf("%d", &number);
if(number != 0){
if (number > 0) {
printf("You entered a positive integer: %d\n",number);
}
else if (number < 0) {
printf("You entered a negative integer: %d\n",number);
}
}
else {
printf("The number is 0 and it is neither positive nor negative.\n");
}
printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}Output:
Body of if...else with only one statement
If the body of if - else has only one statement, you can omit { } in the program. This makes your program look cleaner.
if (condition){
//statement
}
//or
if (condition) //statementExample 1:
int number = 5;
if (number > 0) {
cout << "The number is positive." << endl;
}
else {
cout << "The number is negative." << endl;
}Or
int number = 5; if (number > 0) cout << "The number is positive." << endl; else cout << "The number is negative." << endl;
if - else statement in C / C++ with examples
Here, we have two examples with if - else statement in C/C++. The program is written in C and C++ languages.
Example 1: Find the largest of the 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 <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;
}Output:
Example 2: Check even and odd numbers with if - else statement in C / C++.
C++ programming:
#include <iostream>
using namespace std;
int main() {
int number;
cout << "Enter an integer: ";
cin >> number;
if(number != 0){
if (number %2 == 0) {
cout << "You entered a even number: " << number << endl;
}
else{
cout << "You entered a odd number: " << number << endl;
}
}
else {
cout << "This is zero." << endl;
}
cout<<"\n-------------------------------\n";
cout<<"This program is posted at learnnc.com";
return 0;
}C programming:
#include <stdio.h>
int main(void) {
int number;
printf("Enter an integer: ");
scanf("%d", &number);
if(number != 0){
if (number %2 == 0) {
printf("You entered a even number: %d\n",number);
}
else{
printf("You entered a odd number: %d\n",number);
}
}
else {
printf("This is zero\n");
}
printf("\n-------------------------------\n");
printf("This program is posted at learnnc.com");
return 0;
}Output:
