As the name suggests, a **buffer** is temporary storage used to store input and output commands. All input and output commands are buffered in the operating system's buffer.

## C language's use of a buffer

C uses a buffer to output or input variables. The buffer stores the variable that is supposed to be taken in (input) or sent out (output) of the program. A buffer needs to be cleared before the next input is taken in.

## Code
The following code takes multiple characters in the variables ​`v1` and `v2`. However, the first character is stored in the variable, while the next character is stored in the operating system's buffer.” 

* Sample input: `a b c`
* Stored in variable `v1`: `a`
* Stored in buffer: `b c`
* Stored in `v2`: `b`

#include<stdio.h>
#include<conio.h>
void main()
{
  int v1,v2;
  clrscr();
  printf("\n Enter v1: ");
  scanf("%d",&v1);
  printf("\n Enter v2: ");
  scanf("%d",&v2);
  printf("\n v1+v2=%d ",v1+v2);
  getch();
}

### Output
```c++
Enter v1: 10 

Enter v2: 20 

v1+v2=30 
```

#### Run the program again
```c++
Enter v1: 10 20 30 

Enter v2: (nothing)

v1+v2=30
```

>`v2` is automatically taken from the previous run by the buffer.

​## Code using `fflush(stdin)`
The same input mentioned above is treated differently when the buffer is cleared.

#include<stdio.h>
#include<conio.h>
void main()
{
  int v1=0;
  int v2=0;
  clrscr();
  printf("\n Enter v1: ");
  scanf("%d",&v1);
  printf("\n Enter v2: ");
  fflush(stdin);
  scanf("%d",&v2);
  printf("\n v1+v2=%d ",v1+v2);
  getch();
}

### Output
```c++
Enter v1: 10 

Enter v2: 20 

v1+v2=30 
```

#### Run the program again
```c++
Enter v1: 10 20 30 

Enter v2: (nothing)

v1+v2=10 //10+0=10
```

**`fflush(stdin)`** is needed to flush or clear the input buffer. It is beneficial to clear the input buffer with `fflush(stdin)` before taking the input using the `scanf()` statement​. 

What is a buffer in C?

C language’s use of a buffer

Code

Output

Run the program again

Output

Run the program again