#3 Input and Output in C Programming
Categories - C Programming Tags - C++ C   Maniruzzaman Akash   1 year ago   2012   4 minutes   0

#3 Input and Output in C Programming

Output: We want to print/output anything in C Program.

We've already the basic concept of data types and also get some example of print there. Output means - something print in stdout. We want to print something in C program, so how to do that.


Function name: printf()

printf() is a library function of C, which sends a formatted output to stdout.

Basic printf() function - int printf(const char *format, ...)


Ok, Let's take some practical example of printing in C programming.

Problem 1: We want to print Hello World.

printf("Hello World");

So, here, we've just pass a string as argument and it'll send it to the stdout and it prints - Hello World.


Problem 2: We want to make calculation of two numbers and then print the summation.

int a = 10, b = 20;
printf("Summation = %d", a+b); // Output: Summation = 30

We've used %d as the output variable is integer. We've learned that in previous lesson.


Problem 3: We want to make division of two float numbers and then print the division.


float a = 45.5, b = 5.5;
printf("Division = %f", a/b); // Output: Division = 8.272727

We've used %f because, it is float type value. We've learned that in previous lesson.


Complete Example of summation and division with printing.

#include <stdio.h>

int main(){
    int number1 = 10, number2 = 20, summation;
    summation = number1 + number2;
    printf("Summation = %d\n", summation); // Output: Summation = 30
    float number3 = 45.5, number4 = 5.5, division;
    division = number3 / number4;
    printf("Division = %f\n", number3/number4); // Output: Division = 8.272727

Look at the function now - printf("Division = %f\n", number3/number4)

We've used %f\n, here \n is for new line. And it's a common practice and standard to give new line after a print.


Input: We want to take input from C Program.

Function Name: scanf()

scanf() is a library function in C, which reads input from stdin. Actually it accepts two types of things - 

  1. Format to be taken
  2. Value to be taken

Basic scanf() - int scanf(const char *format, ...)


Practical Example of scanf() :


Problem 1: We want to give a number input and we'll print that number.

#include <stdio.h>

int main(){
    int number;
    printf("Please Enter Number: ");
    scanf("%d", &number);
    printf("Number is: %d", number);
    return 0;


Line By Line Code Description of this input:

  1. First, we print - Please Enter Number:
  2. Then we use - scanf("%d", &number);
    1. We take a number from input using this.
    2. We've used %d, cause it's a decimal/integer value
  3. Then we do - printf("Number is: %d", number);
    1. We print a decimal number and
    2. It'll just print our given number to the input.
  4. Finish program - return 0;


Problem 2: We want to give two number input and we'll print the summation to the output.

#include <stdio.h>

int main(){
    int number1, number2, summation;
    printf("Please Enter Number 1: ");
    scanf("%d", &number1);
    printf("Please Enter Number 2: ");
    scanf("%d", &number2);
    summation = number1 + number2;
    printf("Summation is: %d", summation);
    return 0;

  In here we combined our printf() and scanf() function to do at a time input and output in C programming.


 Problem 3: We want to give multiple number same time in input and we'll print the summation to the output.

#include <stdio.h>

int main(){
    int number1, number2, summation;
    printf("Please Enter Number 1 and 2: ");
    scanf("%d %d", &number1, &number2);
    summation = number1 + number2;
    printf("Summation is: %d", summation);
    return 0;


So, look at this line, how to take multiple input in C programming - 

scanf("%d %d", &number1, &number2);

So, this way, we can take any numbers if we want.


 Problem 4: We want to give first name and last name to the input and print the full name.

#include <stdio.h>

int main(){
   char firstName[30], lastName[15];

   printf("Enter Your First Name: ");
   scanf("%s", firstName);

   printf("Enter your website name: ");
   scanf("%s", lastName);

   printf("Full Name: %s %s\n", firstName, lastName);
   return 0;

So, as it's string we've used %s.

And one more different it's from the previous example. Look in previous example we've used &d, but here only s.


So, we've got enough problem and examples of input and output of C programming. Hope now, it's easy to understand how input and output works in C programming.


Basic and popular format identifiers in C.

Data Type Format Specifier
int %d
char %c
float %f
double %lf
short int %hd
unsigned int %u
long int %li
long long int %lli
unsigned long int %lu
unsigned long long int %llu
signed char %c
unsigned char %c
long double %Lf


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Related Live Coding Examples for testing input/output:

  1. Hello World Print in C Programming
  2. Summation Program in C Programming
  3. Simple Division Program in C Programming
  4. Simple Multiplication Program in C Programming
  5. Simple Subtruction Program in C Programming
  6. All arithematic Program in C Programming


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