Lec2_ConstantVariableDataType_DrHarun050112

7/21/2019 Lec2_ConstantVariableDataType_DrHarun050112

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Constants,Variables & Data

Types

Dr A R M Harunur Rashid


2/22

Theoretical Questions

What is variable? !plain local & "lobal variable#

$rie%ly e!plain basic data types ith e!a'ple & their typical 'e'ory

re(uire'ents#What is an identi%ier? What are the rules %or usin" an identi%ier?

What is the di%%erence beteen )ey* ord & identi%ier? What are

the )ey ords so %ar you have used?

What is sy'bolic constant?


3/22

+ocal & lobal Variables

+ocal lobal

curly brace Declared inside %unction,that is inside curlybraces,i#e# -local varpro"ra' .

Declared outside %unction,that is outside curlybraces,i#e# "lobal varpro"ra'.

use location used by the pro"ra'bloc) inside curly braceused by any pro"ra'se"'ent anyhere in thepro"ra'


4/22

/y'bolic ConstantA sy'bolic constant is de%ined ith a preprocessor directive

that assi"ns an identi%ier to the constant#

Here identi%ier0na'e "iven to the sy'bolic constant1 usually

ritten in all upper case letters#

2t can appear anyhere in a C pro"ra' thou"h usually it is'entioned in the be"innin" o% the pro"ra' a%ter the header

%iles#

The co'piler ill replace each occurrence o% the sy'bolic

constant a%ter it is de%ined ith the constant value assi"ned#

3de%ine sy'bolicna'e value4o%4constant

e#"# 3de%ine 52 6#787

9o /e'icolon


5/22

/trin" constants

nclosed in double (uotes

e#"# :Hello;


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Identifier naming rule:

The identi%iers 'ust con%or' to the %olloin" rules#

7#=irst character 'ust be an alphabet 0or underscore1

>#2denti%ier na'es 'ust consists o% only letters, di"its and

underscore#

6#identi%ier na'e should have less than 67 characters#

8#Any standard C lan"ua"e )eyord cannot be used as avariable na'e#

#identi%ier should not contain a space#

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Character

A character denotes any alphabet,

di"it or special sy'bol# 2n 'ost cases,

space is also considered as character#


9/22

Constants and VariablesCharacter Set: The character set in C +an"ua"e can be "rouped into the %olloin" cate"ories#

7# +etters

># Di"its

6# /pecial Characters

8# White /paces

White /paces are i"nored by the co'piler until they are a part o% strin" constant#

White /pace 'ay be used to separate ords, but are strictly prohibited hile

usin" beteen characters o% )eyords or identi%iers#

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10/22

A constant is an entity that does not

chan"e#

A variable is an entity that 'ay chan"e


11/22

Constants A constant value is the one hich does not chan"e durin" the e!ecution o% a

pro"ra'# C supports several types o% constants#

7# 2nte"er Constants

># Real Constants

6# /in"le Character Constants

8# /trin" Constants

Integer Constants:

An inte"er constant is a se(uence o% di"its#

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12/22

Real Constants:

Real Constants consists o% a %ractional part in their representation#

2nte"er constants are inade(uate to represent (uantities that vary

continuously# These (uantities are represented by nu'bers containin"

%ractional parts li)e >@#B># !a'ple o% real constants are

#>@ *# 86#> E8B#

Real 9u'bers can also be represented by e!ponential notation# The

"eneral %or' %or e!ponential notation isF mantissa e exponent# 2t'eans 'antissa ti'es a poer o% 7 The 'antissa is either a real

nu'ber e!pressed in deci'al notation or an inte"er# The e!ponent is an

inte"er nu'ber ith an optional plus or 'inus si"n# Gsually 'antissa

has an absolute value "reater than or e(ual to 7 and less than 7

#@e8 7>e*> 6#7B6 *7#>e*> 7#eE

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13/22

Single Character Constants:

A /in"le Character constant represent a sin"le character hich is enclosed

in a pair o% (uotation sy'bols# !a'ple %or character constants areF

I I!I IJI I I

All character constants have an e(uivalent inte"er value hich are called

A/C22 Values#

String Constants: A strin" constant is a set o% characters enclosed in double (uotation 'ar)s#

The characters in a strin" constant se(uence 'ay be a alphabet, nu'ber,

special character and blan) space# !a'ple o% strin" constants are

KHi thereLK K7>68K Kod $lessK KL#####?K

Backslash Character Constants [Escape Sequences]:

$ac)slash character constants are special characters used in output

%unctions# Althou"h they contain to characters they represent only one

character#

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14/22

Variables na'in" rule

Any variable declared in a pro"ra' should con%ir' to the %olloin"

7# They 'ust alays be"in ith a letter, althou"h so'e syste's per'it

underscore as the %irst character#

># The len"th o% a variable 'ust not be 'ore than B characters#

6# White space is not alloed and

8# A variable should not be a


15/22

Variable Analo"y

A

77876

$

7787

C

7787B

D

7787

77877>

=778776

/ay, there are

si! seats in a

'icrobus,

na'ely

A,$,C,D,,=#

Today A seat

as bou"ht by

77876

student, $

seat by

7787 and so

on#


16/22

Variable Analo"y

A

7787@

$

77877

C

77877

D

77877

77877B

=77876

/ay, there are

si! seats in a

'icrobus,

na'ely

A,$,C,D,,=#

To'orro A

seat 'ay be

bou"ht by

7787@

student, $

seat by

77877 and so

on#


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/o here the seat location o% A is %i!ed,

the passen"er ho is occupyin" it

chan"in"# /i'ilarly one variable ta)es a speci%ic

location in the co'puter 'e'ory# Here

the value o% the variable 'ay chan"ebut the 'e'ory location o% the variable

in the co'puter ill not be chan"ed#


18/22

Data Types

A C lan"ua"e pro"ra''er has to tell the syste' be%ore*hand, the type o% nu'bers

or characters he is usin" in his pro"ra'# These are data types# There are 'any

data types in C lan"ua"e# A C pro"ra''er has to use appropriate data type as per

his re(uire'ent#

C lan"ua"e data types can be broadly classi%ied as

7#5ri'ary data type

>#Derived data type

6#Gser*de%ined data type

Primary data type:

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7# 2nte"er int

># Character char

6# =loatin" 5oint %loat

atatype

Range of !alues

char *7>B to 7>int *6>@B to E6>@

%loat6#8 e*6B to 6#8eE6B


19/22

Tips

2% a %or'ula or e(uation is used %or

solvin" a proble', all ter's e!cept

nu'bers in the %or'ula should bedeclared as variables#


20/22

Declaration o% Variables

very variable used in the pro"ra' should be declared to the co'piler# The

declaration does to thin"s#

7# Tells the co'piler the variables na'e#

># /peci%ies hat type o% data the variable ill hold#

The "eneral %or'at o% any declaration

datatype v7, v>, v6, ## vnJ

Where v7, v>, v6 are variable na'es# Variables are separated by co''as# A

declaration state'ent 'ust end ith a se'icolon#

E"ampleF

int su'J

%loat nu'ber, salaryJ

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Lec2_ConstantVariableDataType_DrHarun050112

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