c language keywords,variables &constants

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    CONSTANTS,KEYWORDS,VARIABLES &LITERALS

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    PRESENTED BY :

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    C is a programming languagedeveloped at AT& Ts BELLlaboratories of USA in 1972

    It was designed & written by aman named DENNIS RITCHIE

    In the late 70s C began to replacethe more familiar languages ofthat time like PL/I,ALGOL

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    A constant is an entity that doesnt change ,whereas, a variable is an entity that maychange

    Types of constants:

    a)Primary constants

    b)secondary constants

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    Keywords are the words whose meaning hasalready been explained to the C compiler (orin a broad sense to the computer).

    The keywords cannot be used as variablenames because if we do so, we are trying toassign a new meaning to the keyword. whichis not allowed by the computer. some C

    compilers allowed by the computer. Some Ccompilers allow you to costruct variablenames that exactly resemble the keywords.

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    Keywords of C programming

    AutoBreak

    CaseCharConstContinueDefaultDo

    doubleelse

    enumexternFloatForgotoif

    intlong

    registerreturnshortsignedsize ofstatic

    structswitch

    typedefunionunsignedvoidvolatilewhile

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    C constants

    Primary

    constants

    Secondary

    constants

    Integerconstant

    Real constant

    Characterconstant Stringconstant

    ArraysPointers

    StructureUnionEnum

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    1. REAL CONSTANT :

    It must have at least one digit. It must have a decimal point which may be positive or

    negative. Use of blank space and comma is not allowed between

    real constants.

    Example:+194.143, -416.41

    2. INTEGER CONSTANT :

    It must have at least one digit.

    It should not contain a decimal place. It can be positive or negative. Use of blank space and comma is not allowed between

    real constants. Example: 1990, 194, -394

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    3. CHARACTER CONSTANT :

    It is a single alphabet or a digit or a special symbolenclosed in a single quote.

    Maximum length of a character constant is 1. Example:

    'T', '9', '$'

    4. STRING CONSTANT : It is collection of characters enclosed in double quotes.

    It may contain letters, digits, special characters andblank space.

    Example:

    "Techno well Web Solutions, Sangli"

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    An entity that may vary during program executionis called a Variable

    Variables names are names given to locations inmemory

    This locations can contain integer, real or characterconstants.

    For Eg:

    An integer variable can hold only an integer

    constant, a real variable can hold only a realconstant & a character variable can hold only acharacter constant.

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    a) A variable name in any combination of 1 to31 alphabets , digits or underscores. somecompilers allow variable names whoselength could be up to 247 characters.still, it

    would be safer to stick with the rule of 31characters. Do not create unnecessarily longvariable names as it adds to your typingeffort

    b) The first character the variable name mustbe an alphabet or uderscore

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    c) NO commas or blanks are allowed within

    variable named) No special symbol other than a underscore

    be used in a variable name

    for Eg:

    si_int

    m_hra

    pop_e_89

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