C Foundation

What is C? C Compiler Installation C Extensions C Compiler C Interpreter C Program Structure

C Basics

C Keywords C Data Types C Identifiers C Variables C Constant C Escape Sequences C Constant and Volatile C Typecast


What is Operator C Comma Operator C Arithmetic Operators C Relational Operators C Logical Operators C Bitwise Operators C Conditional Operators C : : Operator C Operator Priority

Basic IO's

Basic IO's C Formatted Functions C Unformatted Functions C Common Functions

Control Statements

What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement


What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop


What is Function C User Defined Functions C Recursion C Passing Parameters


Scope C Local Scope C Global Scope

Storage Classes

What is Storage Class C Auto C Extern C Static C Register


What is Array C One Dimensional Array C Two Dimensional Array C Multi Dimensional Array C Arrays Of Strings


What is String C String Functions


What is Pointer C Pointers Arithmetic C Pointer to Pointer C Pointers and Arrays C Pointers and Strings C Pointer to Functions Void Pointers Null Pointers C Null and Void Pointer


What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def


What is Union


What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

Memory Allocation

What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

C Reference

All ASCII Code Basic C Questions

C Interview

C Interview Sets All Star Patterns All Number Patterns All Alphabet Patterns All Series Patterns
The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Reverse Number

We challenge you, the programmer to write a C program to reverse the user entered number. Note, you should not use array concept here.

reverse number

C Program - Reverse Number

Let us workout a program to reverse the user entered number for example: 12345 to 54321

#include <stdio.h>
int main()
int num, reverse = 0;
printf("Enter a number to reverse: ");
while(num != 0)
reverse = reverse * 10;
reverse = reverse + num % 10;
num = num / 10;
printf("\nReverse of entered number is = %d ", reverse);
return 0;
Enter a number to reverse: 135
Reverse of entered number is = 531


Logic is very clear from the above program,

STEP 1: To get last number of the user entered number we are using "%" operator to find the remainder when a user entered number is divided by 10.

Step 2: Now we are dividing the number by 10 to neglect the last part of the user entered number.

Step 3: Repeat step 1 and step 2 until user entered number become zero by calculation.

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