This document discusses different ways to define constants and functions for unformatted input/output in C programming language. It describes: 1. Two ways to define constants using #define preprocessor and const keyword. 2. Functions like getchar(), putchar(), gets(), puts() to get single character and string input from user and display output. 3. Differences between getch(), getche() functions for character input without buffering or echoing.

1. C Programming Language
Defining Constants and Unformatted Input
Output Functions
Dr.G.Jasmine Beulah

2. Defining Constants
There are two simple ways in C to define
constants:
1. Using #define preprocessor.
2. Using const keyword.

3. 1.The #define Preprocessor
This is how to use #define preprocessor to
define a constant:
#define identifier value

4. Example
#include <stdio.h>
#define LENGTH 10
#define WIDTH 5
#define NEWLINE 'n'
void main()
{
int area;
area = LENGTH * WIDTH;
printf("value of area : %d", area);
printf("%c", NEWLINE);
}

5. When the above code is compiled and executed,
it produces following result:
value of area : 50

6. 2.The const Keyword
The const prefix can be used to declare
constants with a specific type as follows:
const datatype identifier = value;
const int len=5;
const float pi=3.14;

7. Example
#include <stdio.h>
void main()
{
const int LENGTH = 10;
const int WIDTH = 5;
const char NEWLINE = 'n';
int area;
area = LENGTH * WIDTH;
printf("value of area : %d", area);
printf("%c", NEWLINE);
}

8. OUTPUT
50

9. Unformatted Input Output Functions
getchar()- int getchar(void)
 This function reads the next available character from the screen and returns it as
an integer.
 This function reads only single character at a time.
 This method can be used in the loop in case you want to read more than one
characters from the screen.
putchar()-int putchar(int c)
 This function puts the passed character on the screen and returns the same
character.
 This function puts only single character at a time.
 This method can be used in the loop in case you want to display more than one
character on the screen.

10. getchar(),putchar()-Example
#include <stdio.h>
void main( )
{
int c;
printf( "Enter a value :");
c = getchar( );
printf( "nYou entered: ");
putchar( c );
}

11. getch(),putch(),getche()
getch() and putch() is also used to input and
output a single character.
getche()echoes the input character but
getch()doesnt echo the input character.
getch() reads a single character from keyboard and displays the
entered character without using enter key , it doesnot buffer any.
getche() reads a single character from the keyboard and displays
immediately on output screen without waiting for enter key.

12. gets(), puts() functions
gets()- char *gets(char *s)
This function reads a line (string) from stdin into the buffer pointed to by s until either
a terminating newline or EOF.
puts()-int puts(const char *s)
This function writes the string s and a trailing newline to stdout.

13. #include <stdio.h>
void main( )
{
char str[100];
printf( "Enter a value :");
gets( str );
printf( "nYou entered: ");
puts( str );
}
gets(), puts() -Example