Programming Fundamentals

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Programming Fundamentals

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Java Character Set

• Character set is a set of valid characters that a
  language can recognize . A character represents
  any letter, digit, or any other sign. Java uses
  the Unicode character set.
• Letters - A-Z, a-z
• Digits - 0-9
• Special Symbols - Space - / \ ( )
  ! lt gt . , ! ?
  _(underscore) lt gt _at_
• White Spaces - Blank spaces, Horizontal
  tab, Carriage return, New line, Form feed.

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Tokens(Lexical units)

• The smallest individual unit in a program is
  known as a Token or lexical unit.
• Types of Tokens -
• Keywords
• Identifiers
• Literals
• Punctuators
• Operators

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Keywords

• Keywords are the words that convey a special
  meaning to the language compiler. These are
  reserved for special purpose and must not be used
  as normal identifier names. E.g if, else, int,
  float, etc.

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Identifiers

• Identifiers are names given to different part of
  the program by user.
• Rules to write identifiers -
• They must not begin with digits.
• No special symbols are used except _(underscore)
  and (dollar sign) character
• They must not be a keyword.
• Java is case sensitive language. Upper case and
  lower case letters are treated differently.
• Examples- myfile , date9_2_7_6

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Literals

• Literals (literals) are data items that are fixed
  data values.
• Types of Literals -
• Integer literal
• Floating literal
• Character literal
• String literal
• Boolean literal
• Null literal

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Integer Literal

• Integer literals are whole numbers without any
  fractional part.
• Three types of Integer literals -
• Decimal Integer literal
• Octal Integer literal
• Hexadecimal Integer literal

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Decimal Integer literal

• An integer literal consisting of a sequence of
  digits is taken to be decimal integer literal
  unless it begins with 0 (digit zero).
• Example- 1296, 5642, 12, 69,-
  23,etc.,

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Octal Integer literal

• A sequence of digits starting with 0(digit
  zero) is taken to be an octal integer.
• Example-0123, 0456, etc.,

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Hexadecimal Integer literal

• A sequence of digits preceded by 0x or 0X is
  taken to be an hexadecimal integer.
• Example- 0x4B6, 0XA43,etc.,

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Floating literals

• Floating literals are also called as Real
  literals
• Real literals are numbers having fractional
  parts. These may be written in one of the two
  forms called fractional form or the exponent
  form.
• Examples-2.0, 3.5, 8.6, etc.,

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Character literals

• A Character literal is one character enclosed in
  single quotes, as in z.
• Examples- a, b, etc.,

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String Literals

• String literal is a sequence of zero or more
  characters surrounded by double quotes( ).
• Examples-a , ade, etc.,

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Punctuators or Separators

• The following characters are used as punctuators.
• ( ) , .

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Operators

• Operators are symbols that perform some action.
  E.g , -, /, etc.