Data types in 'C'
There are 4 basic data types in 'C'.
char - for character type of
data, this can hold a single character. It takes 1 byte in the memory. Declaration
is
char ch;
int - for storing decimal integer
numbers. It takes 2 bytes in the memory. declaration is
int mnum;
float - for storing numbers
with floating point. this can give 6 digits of precision. It takes 4 bytes in
the memory. Declaration is
float mum;
double - for storing numbers
with floating point. this can give 10 digits of precision. It takes 8 bytes in
the memory. Declaration is
double mnum;
void - it is type less and
generally used with user defined functions returning no value.
Modifiers with basic data types:-
A modifier is used to alter the meaning of
base data type to fit various situations. Accept for void the basic data types
can have various modifiers preceding them. These are signed, unsigned, long and
short. All of these can be applied to char and int base types. long can also be
applied to double.
Declarations are as follows:
long int mnum; or long mnum;
- used when a length of more than
the normal integer length is required.
short int mnum; or short mnum;
- used when a length of less than the normal
integer length is required.
unsigned int mnum;
signed int mnum;
Identifier names: - The
names of variables, functions, labels and various other user defined objects
are called identifier names. These names can be of one or more characters. The
first character should be an alphabet or an underscore (_). The subsequent
characters must be alphabets, numbers or underscores. An identifier name can't
be the same as 'C' keyword, a function written by a programmer or in built in
the library.
Data Type size in bits range
char 8 - 128 to 127(in ASCII)
unsigned char 8 0 to 255(in ASCII)
signed char 8 - 128 to 127(in
ASCII)
int 16 -32,768 to 32,767
unsigned int 16 0 to 65,535
signed int 16 -32,768 to 32,767
short int 16 -32,768 to 32,767
unsigned short int 8 0 to 65,535
signed short int 8
-32,768 to 32,767
long int 32 -2147483648 to 2147483647
signed long int 32 --"--
unsigned long int 32 0 to 4294967295
float 32 6 digits of precision
double 64 10 digits of precision
long double 128 10 digits of precision
Input and output functions:-
i) printf() - It prints the comment
and/or output in the specified format on the screen.
ii) scanf() - It accepts input from
the user in the specified format.
iii) getchar() - It reads a
character from the keyboard and waits for carriage return.
iv) getche() - It reads a character
from the keyboard with echo and does not wait for carriage return.
v) getch() - Reads a character
without echo and does not wait for carriage return.
vi) gets() - Reads a string from
the keyboard.
vii) putchar() - It writes a
character to the screen.
viii) puts() - It writes a string to the
screen.
examples :-
1) char chi ;
ch = getchar() ;
putchar(ch) ;
2)
char str[80] ;
gets(str) ;
puts(str) ;
3) puts("Hi ! How are you
?") ;
4) printf("this is %c and
%s", 'C', "Softech") ;
Format specifiers used with
printf() :-
Code Format
%c character
%d signed decimal integers
%i signed decimal integers
%e scientific notation (lowercase e)
%E scientific notation (uppercase E)
%f decimal floating point
%g uses %f or %e whichever is shorter
%G uses %f or %E whichever is shorter
%o unsigned octal
%s string of characters
%u unsigned decimal integers
%x unsigned hexadecimal (lowercase
characters)
%X unsigned hexadecimal (uppercase
characters)
%p displays a pointer
%% prints a % sign
Format specifiers used with scanf()
:-
Code Format
%c reads a character
%d reads a signed decimal integer
%i read signed decimal integers
%e reads a floating point number
%f reads a floating point number
%g reads a floating point number
%o reads an octal number
%s reads a string of characters
%u reads an unsigned decimal integer
%x reads a hexadecimal
%p reads a pointer
%[] scan for a set of characters
examples :- 1) char ch = 'a' ;
printf("%d", ch) ;
output is 97 (Ascii value for 'a')
2) #include <stdio.h>
main()
{
char abc[50] = "Hi ! How
are you ?" ;
float num = 708.89 ;
int full = 801 ;
printf("%s friend ",
abc) ;
printf("no. in signed
integer :%d", full) ;
printf("no. in floating
:%f", num) ;
printf("no. in unsigned
integer :%u", full) ;
printf("no. in scientific
notation :%e", num);
printf("no. in unsigned
octal :%o", full);
printf("no. in unsigned hex
:%x", full);
}
Escape sequence characters :- Used with printf() only.
Code Meaning
\b Backspace
\f Form feed
\n New line
\r Carriage return
\t Horizontal tab
\" To print double quote
\' To print single quote
\0 Null
\\ To print backslash
\v Vertical tab
\a Alert (beep sound)
\N To print octal constant (where N
is any octal
constant)
\xN To print hexadecimal constant
(where N is any
hex. no.)
examples :- ) printf("Life is
\t very short \n & \n there's
\t no time.");
output is - Life is very short
&
there's no time.
Format modifiers :-
Many format specifiers works with
modifiers that alter their meaning slightly. Modifiers are placed between the
percent sign and the format specifier. minimum and maximum field width, the no. of decimal
places, left justification and many other kind of formatting can be specified
using modifiers.
Modifier for minimum field width –
e.g.
#include <stdio.h>
main()
{
float num;
num = 13.4485;
printf("No. is : %f",
num);
printf("No. padded with 10 spaces
is :%10f", num);
printf("No. padded with 0's is
:%010f", num);
}
The program will give following
output :
No. is :13.4485
No. padded with 10 spaces is :
13.448500
No. padded with 0's is :013.448500
The precision specifier –
e.g. 1) %12.5f - used with float
type of data, outputs the no. with
minimum 12 digits and 5
decimal places.
2) %8.12s - used with char. type,
outputs the
string with minimum 8 chars. and
not exceeding 12 chars.
3) %.2f - Displays the output in
floating point number with only 2 decimal places.
Modifier to justify output - By
default numeric output is right justified. To make it left justified do the
following :
e.g. float num ;
num = 12.456;
printf("The no. is
:%5.2f", num);
The output is : The no. is : 12.45
after using modifier to left
justify output :
float num ;
num = 12.456;
printf("The no. is
:%-5.2f", num);
The output is : The no. is :12.45
Modifier for maximum field width -
example as follows :
char str[80] ;
printf("\nenter a
string:") ;
scanf("%10s", &str);
The above segment accepts only the
string which is maximum of 10 characters.
Scanset ([ ]) specifier - e.g.
1) char str[10] ;
scanf("%[abcd]", &str) ; -
Here if you input "alpha", then it will accept only "aa"
because it prohibits to accept the char. other than a,b,c or d.
2) char str[10] ;
scanf("%[^abcd]", &str) ;
- Here if you input "alpha", then it will accept only
"lph" because it prohibits to accept the char. a,b,c or d.
3) char str[10] ; scanf("%[a-z]",
&str) ; - Here if you input
"alpha", then it will accept the whole string "alpha"
because it is meant for accepting all the characters in the range 'a' to 'z'. But it does not accept
"ALPHA".
Some additional modifiers –
1) %ld - for long integer. It applies to
specifiers d, u, x
2) %hd - for short integer. It
applies to specifiers d, u, x
3) * modifier - e.g.
printf("The no.is :%*.*f", 8, 2,130.45);
output is - The no.is: 130.45
- here first * is replaced with 8,
second * is replaced with 2 and no.
130.45 is displayed using these modifiers.
* modifier can also be used for
suppressing input. e.g.
scanf("%d %*c %d",
&a, &b) ;
In the above segment, first number
will be accepted in variable 'a', then a char. is accepted and discarded and
second number will be accepted in 'b'. i.e. if you give 1-10
1 gets stored into a and 10 gets
stored into b, - is accepted and discarded.
