C provides a library of functions. This library is called a standard input output library. It is denoted by stdio. The header file containing such library functions is called stdio.h.
There are
two types of input- output functions.
They are :
1.
Formatted
I/O functions
2.
Unformatted
I/O functions
FORMATTED
OUTPUT STATEMENT
C provides the printf( ) function to display the data on the
monitor. The printf( ) is included in stdio.h. It is used to display the results and messages on the screen.
The general form of printf( ) statement is :
printf(“control
string”, varlist);
where,
control string – specifies the type and format of the values to be
displayed. varlist – a list of variables to be displayed.
Example :
printf(“Programming is an Art”); printf(“%d”,sum);
printf(%f%f”,p,q); printf(“\nSum=%d”,sum);
The following are different format descriptors: Conversion
Character Meaning
%d
Print & Read a decimal integer
%u Print & Read a unsigned integer
%s
Print & Read a string
%f
Print & Read a floating point number
%e
Print & Read a exponential floating point
number
%c
Print & Read a single character
%g
Print & Read a floating point number
%i Print & Read a decimal or octal or hexadecimal
%x
Print & Read a hexadecimal number
%h
Print & Read a short integer number
%o
Print & Read octal integer number
%p
Print & Read pointer
FORMATTED
INPUT STATEMENT
To read the values for the variables in a program from the
keyboard, C provides a function called scanf( ). This is used to accept
numeric, character and string type of data. The address operator &
(ampersand) is used to locate the values into variable memory.
Syntax :
scanf(“control
string”, address_list); where
control string – It is a sequence of one or more character group.
Each character is a combination of % symbol and a conversion character.
address_list – Address of memory locations where the values of
input variables should be stored.
Example :
scanf(“%d”,&num);
scanf(“%d%f%c”,&a,&b,&c);
scanf(“%d%s”,&number,name);
Program to add two numbers.
#include<stdio.h>
#include<conio.h>
main()
{
int a,b,sum; clrscr();
printf(“Enter two numbers\n”); scanf(“%d%d”,&a,&b);
sum=a+b;
printf(“\nSum = %d”,sum); getch();
}
Program
to accept three numbers and compute their sum and average.
#include<stdio.h> #include<conio.h> main()
{
int num1,num2,num3,sum; float average;
clrscr();
printf(“Enter thre enumbers\n”); scanf(“%d%d%d”,&num1,&num2,&num3);
sum=num1+num2+num3; average=sum/3;
printf(“\nThe Sum = %d”,sum); printf(“\nThe Average =
%f”,average);
getch();
}
Program
to find the simple interest : #include<stdio.h>
#include<conio.h>
main()
{
int p,t,r; float si; clrscr();
printf(“\nEnter the Principal
:”); scanf(“%d”,&p);
printf(“\nEnter the Term :”); scanf(“%d”,&t);
printf(“\nEnter the Rate :”); scanf(“%d”,&r);
si=(p*t*r)/100;
printf(“\nThe Simple Interest = %f”,si);
getch();
}
Program
to accept the temperature in Fahrenheit and convert it into Celsius.
#include<stdio.h> #include<conio.h> main()
{
float ct, ft; clrscr();
printf(“Enter the temperature in Fahrenheit\n”);
scanf(“%f”,&ft);
ct=(ft-32.0)/1.8;
printf(“Fahrenheit temperature = %6.2f\n”, ft);
printf(“Celsius temperature = %6.2f\n”, ct);
getch();
}
UNFORMATTED
INPUT FUNCTIONS
These functions are primarily concerned with reading the character
type data from the keyboard.
The getchar( ) and get( ) functions are used for this purpose.
Since, they are included in the stdio.h, the C programs that use these
functions should exclusively have the following preprocessor statement.
#include<stdio.h>
THE getchar( ) FUNCTION
This function reads a single character from the standard input
device. There is no parameter within the parentheses.
Its
syntax is as follows :
ch_var
= getchar( );
Where,
ch_var is a character type variable to which an accepted character is assigned.
Example :
void main( )
{
char letter;
letter =
getchar( );
printf(“Your
character = %c”, letter);
}
THE
gets( ) FUNCTION
This function reads in everything you enter from the keyboard
until the ENTER key or RETURN is pressed. Here, everything means a string which
is a sequence of all printable ASCII characters. The RETURN key that you
pressed will not be stored at the end of the string. It overcomes the limitation
of the scanf( ) statement with %s option. The syntax of gets( ) is gets(string);
Where,
string € is a sequence of characters and it is of type char.
Example
:
void main( )
{
Char ; name[25]; printf(“Enter your name\n”); gets(name);
printf(“Your
Name = %s”, name);
}
UNFORMATTED
OUTPUT FUNCTIONS
These functions are mainly concerned with displaying or printing
the character type data on the monitor. The putchar( ) and puts( ) functions
are used for this purpose. Both these functions are defined in the header file
<stdio.h>
THE
putchar( ) FUNCTION
This function prints a single character on the screen. The
character to be displayer is of type char. Its syntax is as follows.
putchar(ch_var);
Where,
ch_var € is a character variable which is enclosed within the parentheses.
Example
:
void main( )
{
char letter;
letter = getchar( ); putchar(letter);
}
THE
puts( ) FUNCTION
This function prints a string of characters on the screen. The
newline character that signals the end of the string will not be displayed. The
syntax of puts( ) is as follows:
puts(string);
Where,
string € is a sequence of characters.
Example
:
void main( )
{
char
message[20];
printf(“Enter the message to motivate students\n”); gets(message);
puts(message);
}
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