CMPE - L3

• Character set


  is a set of alphabets, letters and some special characters that are valid in C language.
• Alphabets


  C accepts both lowercase and uppercase alphabets as variables and functions
• Digits


  0123456789
• Special Characters

  
• White space Characters


  blank space, new line, horizontal tab, carriage return and form feed
• C Keywords


  Keywords are predefined, reserved words used in programming that have special meanings to the compiler. Keywords are part of the syntax and they cannot be used as an identifier.
• keywords in c language

  • auto
  • break
  • case
  • char
  • continue
  • do
  • default
  • const
  • double
  • else
  • enum
  • extern
  • for
  • if
  • goto
  • float
  • int
  • long
  • register
  • return
  • signed
  • static
  • sizeof
  • short
  • struct
  • switch
  • typedef
• keywords in c language

  union

  void

  while

  volatile

  unsigned
• C identifiers


  It refers to name given to entities such as variables, functions, structures etc.
• Identifier


  must be unique. They are created to give unique name to a entity to identify it during the execution of the program.
• Rules for writing an identifier

  1. A valid identifier can have letters (both uppercase and lowercase letters), digits and underscores.
  2. The first letter of an identifier should be either a letter or an underscore. However, it is discouraged to start an identifier name with an underscore.
  3. There is no rule on length of an identifier. However, the first 31 characters of identifiers are discriminated by the compiler
• Variables


  a variable is a container (storage area) to hold data.
• Rules for naming a variable in C

  1. A variable name can have letters (both uppercase and lowercase letters), digits and underscore only.
  2. The first letter of a variable should be either a letter or an underscore. However, it is discouraged to start variable name with an underscore. It is because variable name that starts with an underscore can conflict with system name and may cause error.
  3. There is no rule on how long a variable can be. However, only the first 31 characters of a variable are checked by the compiler. So, the first 31 letters of two variables in a program should be different
• constant


  is a value or an identifier whose value cannot be altered in a program.
• Integer constants


  An integer constant is a numeric constant (associated with number) without any fractional or exponential part.
• There are three types of integer constants in C programming:

  •decimal constant(base 10)

  •octal constant(base 8)

  •hexadecimal constant(base 16)
• In C programming, octal constant starts with a 0 and hexadecimal constant starts with a 0x.
• Floating-point constants


  is a numeric constant that has either a fractional form or an exponent form.
• Character constants


  A character constant is a constant which uses single quotation around characters.
• Escape Sequences


  The backslash (\) causes "escape" from the normal way the characters are interpreted by the compiler.
• backspace


  \b
• \f

  form feed
• \n


  newline
• \r

  return
• \t

  horizontal tab
• \v

  vertical tab
• \\

  backslash
• \'

  single quotation mark
• \"

  double quotation mark
• \?

  question mark
• \0

  null character
• String constants


  String constants are the constants which are enclosed in a pair of double-quote marks.
• //string constant


  "good"
• null string constant


  ""
• string constant of six white space


  " "
• "x"

  string constant having single character
• Enumeration constants


  define enumeration types
• Fundamental Types

  • Integer
  • Floating
  • Character
• Derived Typess

  • Arrays
  • Pointers
  • Structures
  • Enums
• int - Integer data types

  whole numbers that can have both positive and negative values but no decimal values.