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Constants

Posted By: Morgan Brown     Category: C Programming     Views: 6008

This article explains about constants with example in C programming.

Constants in C



Integer Constants

  • An integer constant refers to a sequence of digits
  • There are three type of integers Decimal, Octal and Hexadecimal
  • Decimal integers consists of set of digits, preceded by optional + or - sign
  • Embedded spaces, commas, and non digit characters are not allowed

Examples of Integer Constants

 Valid Constants

  Invalid Constants 

 123

 987612347ul

 15 750

 

 -321

987612347UL

 20,000

 

 0

+78

 $1000

 

 65432L

0xAB

089 

 

 545U

0X10A

0xGH 

 

 545u

035

12.5 

 

 567891

 

 

 


Examples of Valid Real Constants

 0.0083

0.65e4 

 -0.75

12e-2 

 435.36

1.5e+5 

 +247.0

3.18E3--Underline word is Exponent 

 -.75

-1.2e-1 --Underline word is Mantissa 

 .95

Embedded space is not allowed 


Examples of Numeric Constants

 Constant

 Valid 

 Remarks

 698354L

 Yes

 Long integer 

 25,000

 No 

 , not allowed

 +5.0E3

 Yes

 Unary + allowed 

 3.5e-5

 Yes

 

 7.1e4

 No 

 White space NA 

 -4.5e-2

 Yes

 

 1.5E+2.5

 No

 Exp must be int

 $255

 No

 $ not allowed

 0X7B

 Yes 

 Hexadecimal int


Single Character Constants

  • A (single) character constant contains a single character within pair of single quotes
  • ‘5’  ‘X’ ‘;’  ‘ ‘     are examples of character constants
  • Note that ‘5’ is different than 5
  • Character constant have integer values, known as ASCII values
  • Printf (“%d”,’a’); and printf(“%c”,97);

String Constants

  • Is a sequence of characters enclosed in double quotes ex. “Hello!” or “1997”
  • ‘x’ is different than “x”!
  • A character string does not have any ASCII value associated with it
  • Few other examples are “Well Done!” “?..!” “5+3” “!@$”

Backslash Character Constants

 Constant

 Meaning

 Constant

 Meaning

 '\a'

 Audible alert

 '\v'

 Vertical tab

 '\b'

 Back space

 '\''

 Single quote

 '\f'

 Form feed

 '\'"

 Double quote

 '\n'

 New line

 '\?'

 Question mark

 '\r'

 Carriage return

 '\\'

 Back slash

 '\t'

 Horizontal tab

 '\0'

 Null


Symbolic Constants

  • The scanf() function and &
  • Defining symbolic constants
  • Modifiability and understandability
  • Usually written in capitals
  • # is needed but ; is not allowed in the end
  • Assignment statement is not allowed
  • It can reside anywhere before usage

  
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Morgan Brown
Morgan Brown author of Constants is from London, United Kingdom.
 
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