Defining Constant,Unformatted input output functions

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