The constants refer to fixed values that the program may not
change during its execution. These values are also called literals.
Constants can be of any of the data types like an integer , a floating , a
character , a string literal and an enumeration constants as well.
The constants are consider just like regular variables
except that their values can't be modified after their definition.
Integer literals:
An integer literal can be of any number system 1.e a
decimal, octal, or hexadecimal constant. A prefix specifies the base or radix
are :
1.0x or 0X for hexadecimal,
2.0 for octal.
3.and nothing for decimal.
An integer literal can also have a combination of unsigned(U) and long(L), respectively. The
suffix can be in uppercase or in lowercase and can be in any order.
some examples of
integer literals are:
2123 /* Legal */
2145u /* Legal
*/
0xFeeL /* Legal
*/
0718 /*
Illegal: 8 is not an octal digit */
032UU /*
Illegal: cannot repeat a suffix */
The various types of
Integer literals are:
85 /* decimal
*/
0213 /* octal */
0x4b /*
hexadecimal */
30 /* int */
30u /* unsigned int */
30l /* long */
30ul /* unsigned
long */
Floating-point literal:
Floating-point
literals must contain a decimal point,an integer part, a fractional part, and
an exponent part.Floating point literals can be represent either in decimal
form or exponential form.
When you representing
using decimal form, you must consider the decimal point, the exponent, or both
and while using exponential form, the literal
must have the integer part, the
fractional part, or both. The signed exponent is introduced by e or E.
Example are:
3.14159 /* Legal
*/
314159E-5L /* Legal
*/
510E /*
Illegal: incomplete exponent */
210f /*
Illegal: no decimal or exponent */
.e55 /*
Illegal: missing integer or fraction */
Character constants:
Character literals are enclosed within single quotes, e.g.,
'a' and can be stored in a variable of char type.
A character literal can be a plain character (e.g., 'a'), an
escape sequence (e.g., '\n'), or a universal character (e.g., '\u02C0').
Some characters in C
are preceded by a backslash they will have special meaning and they are
used to represent like newline (\n) or tab (\t). Following are the some escape sequence codes:
Escape sequence Meaning
\\ \
character
\' '
character
\" "
character
\? ?
character
\a Alert or
bell
\b Backspace
\f Form feed
\n Newline
\r Carriage
return
\t Horizontal
tab
\v Vertical
tab
\oo Octal
number of one to two digits
\xhh . . . Hexadecimal
number of one or more digits
Example using escape sequence:
#include <stdio.h>
int main()
{
printf("Hey\tWorld\n\n");
return 0;
}
Out put:
Hey World
String literals:
String literals or constants are enclosed within a double
quotes "".
You can also break a long line into multiple lines using
string literals and separating them using whitespaces.
Some examples of string literals are:
"hello, dear"
"hello, \
dear"
"hello, " "d" "ear"
Defining Constants
The two simple ways to define a constant in are:
1.Using preprocessor
(#define):
2.Using const keyword.
The #define Preprocessor:
the form to use
#define preprocessor to define a constant is:
#define identifier value
example :
#include <stdio.h>
#define LENGTH 10
#define WIDTH 5
#define NEWLINE '\n'
int main()
{
int area;
area = LENGTH *
WIDTH;
printf("value
of area : %d", area);
printf("%c", NEWLINE);
return 0;
}
Output of the above c program is:
value of area : 50
The const Keyword:
You can use const keyword prefix to declare constants with a
specific type :
const type variable = value;
example:
#include <stdio.h>
int main()
{
const int LENGTH = 10;
const int WIDTH
= 5;
const char NEWLINE
= '\n';
int area;
area = LENGTH *
WIDTH;
printf("value
of area : %d", area);
printf("%c", NEWLINE);
return 0;
}
Output:
value of area : 50
|
|||
| C - Overview | |||
| C - Basic Syntax | |||
| C - Data Types | |||
| C - Variables | |||
| C - Constants | |||
| C - Storage Classes | |||
| C - Operators | |||
| C - Decision Making | |||
| C - Loops | |||
| C - Functions | |||
| C - Scope Rules | |||
| C - Arrays | |||
| C - Pointers | |||
| C - Strings | |||
| C - Structures | |||
| C - Unions | |||
| C - Bit Fields | |||
| C - Typedef | |||
| C - Input & Output | |||
| C - File I/O | |||
| C - Preprocessors | |||
| C - Header Files | |||
| C - Type Casting | |||
| C - Error Handling | |||
| C - Recursion | |||
| C - Variable Arguments | |||
| C - Memory Management | |||
| C - Command Line Arguments |
Sunday, 24 November 2013
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