CHAPTER - 3 : MANAGING INPUT – OUTPUT STATEMENTS
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 :
where,
scanf(“control string”, address_list);
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 three numbers\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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