Lecture 8- Data Input and Output

Data Input and Output
Md. Imran Hossain Showrov (showrovsworld@gmail.com)
8
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Outline
 Input/Output Functions
 Single Character Input
 Single Character Output
 The scanf Function
 The printf Function

Input/Output Functions
 There are several library functions which includes a
number of input/output functions.
 Six common functions are: getchar, putchar, scanf,
printf, get and puts.
 These six functions permit the transfer of
information between the computer and the standard
input/output devices.

Single Character Input- The getchar Functions
 Single character can be entered into the computer
using getchar.
 It returns a single character from standard input
device(typically keyboard).
 Can be represented as:
character variable = getchar()
 Where, character variable refers to some previously
declared character variable.

Single Character Input- The getchar Functions
(cont..)
 Example:
char c;
………
c = getchar();
The first statement declares that c is a character-type
variable. The second statement causes a single character to
be entered from the standard input device and then assigned
to c.

Single Character Output- The putchar Functions
 Single character can be displayed using putchar.
 This function is complementary to the character input
function getchar.
 It transmits a single character to a standard output device.
 Can be represented as
putchar(character variable)

Single Character Output- The putchar Functions
(cont..)
 Example:
char c;
………
putchar();
The first statement declares that c is a character-type variable. The
second statement causes the current value of c to be transmitted to
the standard output device where it will be displayed.

Example 1: getchar and putchar
#include<stdio.h>
#include<ctype.h>
main()
{
char ch;
printf(“Enter any character value: ”);
ch = getchar();
printf(“The equivalent upper case: ”);
putchar(toupper(ch));
}

Example 1: getchar and putchar (cont..)
This program converts lowercase to uppercase.
Sample input: a
Sample output: A
Sample input: d
Sample output: D
Sample input: l
Sample output: L

Entering Input Data- The scanf Function
 The scanf() function reads data from the standard
input stream stdin into the locations given by each
entry in argument-list.
 A non-whitespace character causes the scanf()
function to read, but not to store, a matching non-
whitespace character.

The scanf Function
 The skeletal structure is:
#include<stdio.h>
main()
{
int a,b,c;
…………..
scanf(“%d %d %d”, &a, &b, &c);
………………..
}

The scanf Function (cont..)
 Consider the last skeleton-
When the program is executed, three integer quantities will be entered
1 2 3
Then the following assignments will result:
a = 1, b = 2, c = 3
If the data had been entered as
123 456 789
Than the assignment would be
a = 123, b = 456, c = 789

 Example:
#include<stdio.h>
main()
{
int i;
float x;
char c;
…………….
scanf(“%3d %5f %c”, &l, &x, &c);
………………………
}

 If the data items are entered as
10 256.875 T
When the program is executed, then 10 will be assigned to I,
256.8 will be assigned to x and the character 7 will be assigned to
c. The remaining two input characters (5 and T) will be ignored.

The printf Function
 Output data can be written from the computer onto a
standard output device using the library function printf.
printf(control string, arg1, arg2, ….. , argn)
 Where control string refers to a string that controls
formatting information, and arg1, arg2…… argn are
arguments that represent the individual output data
items.

The printf Function (cont..)
 Commonly used conversion characters for data i/o

 The following C program illustrates the use of the minimum field
width feature,
#include<stdio.h>
main()
{
int i = 12345;
float x = 345.678;
printf(“%3d %5d %8dnn”,i,i,i);
printf(“%3f %10f %13fnn”,x,x,x);
}

 When the program is executed, the following output is
generated
12345 12345 12345
345.678000 345.678000 345.678000
 The first and second line of output displays a decimal
integer using three different minimum field widths.

Lecture 8- Data Input and Output

Lecture 8- Data Input and Output

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Lecture 8- Data Input and Output