Input/output Statements and Operators

 Input/output Statements and Operators

Reading data from input device and displaying the result on the screen are

the two main tasks of any programming. In ‘C’ language the input output

operations are carried out by using standard functions. The programs for these

functions are kept in the file. This file must be included in the program to use

these functions using the preprocessor directive as:

#include<stdio.h>

The i/o functions are classified into 2 types:

1) Formatted functions

2) Unformatted functions.

Formatted input output function

The formatted I/O functions read and write all data values.

 Formatted Input:

Scanf():

This formatted input function which read the data from the standard input

into variable in different formats by the user.

Syntax:

 Input single value from user

scanf(“ control string”, &args);

 Input multiple values

scanf(“ control string”, &arg1, &arg2, …. ,&argn);

Example:

 Input single value from user

int no;

scanf(“%d” ,&no);

 Input multiple value

float no 1;

int no 2;

scanf(“%f%d”, &no1, &no2);

Note:

 It reads all types of data values.

 It is used for run time assignment of variable.

 The & (ampersand) symbol is used to indicate the memory

location of the variable. So that the value read would be

placed at that location.

 The control string may contain format code, escape

sequence & width specifiers.

 The format code specifies the type of input data.

 For each variable there must be a format code.

Code Meaning

%c Read a single character

%d Read decimal integer

%f Read a floating point value

%s Read a string

%o Read octal integer

%x Read hexadecimal integer

%u Read an unsigned decimal integer

Example:

Write a program to add two numbers and take input from user

(prog1.c)

#include<stdio.h>

#include<conio.h>

void main()

{

int no1,no2,no3;

clrscr();

printf("Enter two numbers\n");

scanf("%d%d",&no1,&no2);

no3=no1+no2;

printf("sum is %d",no3);

getch();

}

Example:

Write a program to find out Total marks.(prog2.c)

#include<stdio.h>

#include<conio.h>

void main()

{

int m1,m2,m3,m4,m5;

int total;

clrscr();

printf("Enter marks1 ");

scanf("%d",&m1);

printf("Enter marks2 ");

scanf("%d",&m2);

printf("Enter marks3 ");

scanf("%d",&m3);

printf("Enter marks4 ");

scanf("%d",&m4);

printf("Enter marks5 ");

scanf("%d",&m5);

total =m1+m2+m3+m4+m5;

printf("Total marks is %d\n",total);

getch();

}

Note:

Field width w can be used with scanf() function.

 Inputting Integer Number

The field specifier %wd is used to read fixed width integers.

Here w is the width of data needs to be read and store into a

particular variable. Any unread data in a line is considered as input

to the next scanf() call.

Example:

Scanf(“%2d %5d”, &no1, &no2);

Input data is 30 23499

Then the value 30 is assign to no1

And

23499 is assigning to no2.

input data is 23499 30

Then variable no1 will assigned

23(because %2d)

And no2 will assign 499.

The value 30 that is unread will be

assigned to the first variable in next

scanf().

Example: Use of field Width with scanf(). (prog3.c)

#include<stdio.h>

#include<conio.h>

void main()

{

int x,y;

clrscr();

printf("Enter the value of x and y");

scanf("%3d%2d",&x,&y);

printf("------------------");

printf("%d\n%d",x,y);

getch();

}

Output:

Execution 1:

234 // reads 3digit integer into x with field width of 3 (%3d)

56 // reads 2digit integer into y with field width of 2 (%2d)

——————

234

56

Execution 2:

345 78 // reads 3digit integer into x and 78 is input to next scanf() call

——————

345

78

Execution 3:

2654 87 // reads 3digit integer 265 into x and 4 is input to next scanf()

call

——————

265

4

Execution 4:

6534 //reads 3digit integer 653 into x and 4 is input to next scanf() call

——————

653

4