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Constants

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Constants

  1. 1. CONSTANTS IN C
  2. 2. TYPES OF C CONSTANTS C Constants Primary Constants Secondary Constants Integer Constants Array, Pointer , Real Constants Structure , Union Character Constants Enum etc. String constants Escape sequence *CONSTANT is a Quantity that doesn’t change……
  3. 3. INTEGER CONSTANTS  - sequence of digits  Three types  Decimal: set of digits,0 through 9  123, -87, 0, +56 <- valid $1000, 15 750, (20,000) <-Invalid  Octal: combination of 0 to 7 with leading zero. i.e. 075, 051 are octal  Hexadecimal: sequence of digits 0-9,A..F/a..f ….. Preceded by 0x or 0X  like 0x2, 0x3A, 0Xe5,etc are hexadecimal numbers.
  4. 4. REAL CONSTANTS(FLOATING POINT)  - to represent varying entity like prices. it contain fractional parts.  in decimal notation 34.32, -0.56, .4555 , 0.00054 etc.  In exponential notation(or scientific) 215.65 may be written as 2.1565e2 also valid  More 0.65e4 ,12e-2, 3.18E3.  -> Should the following be valid ?  1.5E2.5 (YES / NO ) ?
  5. 5. SINGLE CHARACTER CONSTANTS  -a single character enclosed within a pair of single quote marks I.e ‘y’ , ‘4’, ‘;’ , ‘ ‘, etc.  - character constants have integer values known as ASCII (American Standard Code for Information Interchange) values.  i.e. printf(“%d”,’a’); will print no. 97, the ascii value of the letter a.  While printf(“%c”,97); will print --- a  *error in book statement instead of ’97’ it should be only 97
  6. 6. STRING CONSTANTS  -sequence of characters enclosed in double quotes like  “hello!” , “hi 18”, “well done”, “a”  Remember that “x” and ‘x’ is different because ‘x’ has equivalent integer value in ASCII.  String constants are normally used like displaying menu/messages.
  7. 7. BACKSLASH CHARACTER CONSTANTS  - used in output functions…  - ‘n’ stands for new line character  - ‘b’ for back space  - ‘t’ for making horizontal tab  all above represents one character, although they consist of two chars.  These char combination are known as “escape sequences”

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