Managing input and output-discussion

MANAGING INPUT AND OUTPUT OPERATIONS

All input/output operations are carried out through functions called as printf and

scanf. There exist several functions that have become standard for input and output

operations in C. These functions are collectively known as standard i/o library. Each

program that uses standard I/O function must contain the statement

#include<stdio.h>

The file name stdio.h is an abbreviation of standard input-output header file.

READING A CHARACTER

Reading a single character can be done by using the function getchar. The getchar

takes the following form:

variable_name = getchar();

Program::

/*Reading a character from terminal*/

#include<stdio.h>

main()

{

char ans;

printf(“Would you like to know my name? \n”);

printf(“Type Y for yes and N for no”);

ans=getchar();

if(ans ==’Y’ || ans = =’y’)

printf(“\n\n My name is India \n”);

else

printf(“\n\n You are good for nothing \n”);

}

OUTPUT

Would you like to know my name?

Type Y for yes and N for no:Y

My name is India

Would you like to know my name?

Type Y for yes and N for no:n

You are good for nothing

WRITING A CHARACTER::

Like getchar, there is an analogous function putchar for writing characters one at a

time to the terminal. It takes the form as shown below:

putchar (variable_name);

Program

/*A program to read a character from keyboard and then prints it in reverse case*/

/*This program uses three new functions:islower,toupper,and tolower.

#include<stdio.h>

#include<ctype.h>

main()

{

char alphabet;

printf(“Enter an alphabet”);

putchar(‘\n’);

alphabet = ghetchar();

if(islower(alphabet))

putchar(toupper(alphabet));

else

putchar(tolower(alphabet));

}

OUTPUT

Enter An alphabet

a

A

Enter An alphabet

Q

q

Enter An alphabet

z

Z

Reading Mixed Data Types

It is possible to use one scanf statement to input a data line containing mixed mode

data. In such cases, it should be ensured that the input data items match the control

specifications in order and type.

Eg: scanf(“%d %c %f %s”,&count, &code, &ratio, &name);

Scanf Format Codes

Code                             Meaning

%c                                  Read a single character

%d                                  Read a decimal integer

%e                                 Read a floating point value

%f                                  Read a floating point value

%g                                 Read a floating point value

%h                                 Read a short integer

%i                                   Read a decimal, hexadecimal, or octal integer

%o                                  Read an octal integer

%s                                   Read a string

%u                                 Read an unsigned decimal integer

%x                                   Read a hexa decimal integer

%[..]                                Read a string of word(s)

FORMATTED OUTPUT

The printf statement provides certain features that can be effectively exploited to control

the alignment and spacing of print-outs on the terminals.The general form of printf statement

is

printf(“control string”,arg1, arg2…argn);

Mixed Data Output

It is permitted to mix data types in one printf statements.

Eg: printf(“%d %f %s %c”,a, b, c, d);