Constants, Variables,& Keywords

8/8/2019 Constants, Variables,& Keywords

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Learning steps

Constants and Variable

Types of constants and Variables How to Identify Types

Rules for creating Variables

Keywords


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Learning Stepsy Learning C# language is similar to learning English

y It begin with Alphabets and digits.

yAlphabets to form words, words to form sentencesand sentences to form paragraph and the processcontinues

y Digits forms different numbers.


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The following help in building C# language

Alphabets, Digits and Special Symbols.

Constants & Variables Data Types.

Keywords


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Alphabets, Digits and Special

Symbolsy C# allows all alphabet irrespective of they are capital

letter i.e A-Z or small case letters .i.e a-z.

y Digit ranging from 0-9.y 32 special symbol in the keyboard.


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Constants&VariablesyAlphabets, digits and special symbols are combined to

form constants and variables.

y For example 3x+2y where 3and 2 are constants astheir values does not change ,they are also called asliterals.

y variables are x and y as their values changes ,they are

also called as identifiers.


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ConstantsThere are three types of Constants.

y Integer Constants

y Real Constantsy Character Constants


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Integer Constantsy Example of Integer constants are 23, 56, 678 etc.

Rules for creating Integer Constant

It should not have decimal point. It can be either +ve or-ve The default is +ve.

Within integer constant their should not be commaand space.

The valid range of integers constants is -2147483648 to+2147483647.


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RealConstantsy It must have decimal point present.

y It can be +ve or-ve. The default is +ve.

y There should not be a comma or space within realconstant.

yValid range of real constants is -3.4*1038 to +3.4*1038

y For example 427.62, -0.00254 can be expressed in the

form 4.2762E2,-2.54e-3 etc.

y The first form is fractional form and second form isknown as exponential form.


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Character ConstantsyWhen a character, digit or special symbol is written

within a pair of single inverted commas form a

character constant.y It can be capital letter, small case letter, a digit or

special symbol within single inverted commas.

y For example

y Zy Nagpur is not a character constant it is string

constants


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String Constantsy String constants are enclosed in double quotes

string message = Hello;

y for example Nagpur.


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Types ofConstants

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Character constants char c = z

Numeric constants int a = 10;

Hexadecimal constants int hex = 0xFF;

Octal constants int oct = 011;

String constants char greetings = Hello;

Backslash constants \b, \f, \n, \r, \t, \, \, \0, \\,

\v, \a, \?, \OCTAL, \xHEX


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C# Data Types-PrimitivesData Types Ranges sizes

char 0 t0 65535 2

sbyte -128 to +127 1

short -32768 to +32767 2

int -2147483648 to+2147483647

4

long -9223372036854775808 to+92233720368547758087

8

float -3.4e38 to +3.4e38 4

double -1.7e308 to + 1.7e308 8

bool True/false 1


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VariablesyA name given to memory location whose value

changes is called as variable.

yNo of variables are equal to no of constants.

y for example

y x=3,y=4

y Z=x+y


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How to identify Typesy 3 Integer Constant

y 3.0 Real Constant

y 3 Character Constant

y int a float b char c

y a=3 b=3.0 c=3

y int ,float ,char data types /primitives

y a,b,c variables

y 3,3.0,3 constants/literals


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Rules for Building var. Namesy Cannot begin with a digit

y Rest can be alphabets,digits,underscores or $

y Ex pop98 , si_intyAny length.

y No commas or spaces.

yVariable names are case sensitives

y for example the following are consider differentvariables

y abc ABC Abc aBc AbC


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C# keywordsyWords whose meaning already stands explained to

machines are called as Keywords.

y77 keywords available in c#.

y int,float and char are keywords

y Reserved are same as keywords.

y Following declaration of variable will not work

y integer a

y real b

y character c


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y Proper declaration of variable which machineunderstands is

yint a

y float b

y char c

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