P3_DataTypesAndStorageClassInC

8/3/2019 P3_DataTypesAndStorageClassInC

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Primary Data typesPrimary Data types

Integerlong

short

signed

Unsigned

CharSigned

Unsigned

Floats and Doubles


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Note: use sizeof() function to check the bytes occupied by the data types


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Types of C VariablesTypes of C Variables

Particular type of variable can hold only

the same type of constant.

Integer variable holds only integerconstant

Rules for constructing different types of

constant varies whereas for constructing

variable names of all types the same set of

rules apply.


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Rules for constructing variable namesRules for constructing variable names

Variable name is combination of 1 to 31alphabets,digits or underscores.

Maximum length is 31 characters

First character must be an alphabet orunderscore

No commas or blanks allowed

No special symbol other than anunderscore can be used.

Ex. : si_int , m_hra , si_intr_2008


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Rules for constructing variable namesRules for constructing variable names

It is compulsory to declare the type ofvariable before use in the program.This

type declaration is done at the beginning.

Example of type declaration.int si, m_hra ;

float bassal ;

char code ;


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Storage ClassesStorage Classes--TypesTypes

Automatic

Register

Static External


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Storage ClassesStorage Classes

All variables in C has a storage class.

If u dont specify the storage class for the

variable, compiler will assume the storageclass depending on the context in which

the variable is used.

Two types of locations where a value is

stored in computer.Memory

Register


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Storage ClassesStorage ClassesStorage

Classes and itsimportance

Storage Initial value Scope Life

Automatic Memory Garbage

value

Local to the

block in which

it is defined

Till the control

remain within

the block

Register CPURegisters

Garbagevalue

Local to theblock in which

it is defined

Till the controlremain within

the block

Static Memory Zero Local to the

block in which

it is defined

Value persists

between

different

function calls

External Memory Zero Global As long as

program is

running


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Storage ClassStorage Class -- AutomaticAutomatic

main( )

{

auto int i = 1 ;

{

auto int i = 2 ;{

auto int i = 3 ;

printf ( "\n %d ", i ) ;

}

printf ( "%d ", i ) ;}

printf ( "%d", i ) ;

}Output:321


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Storage ClassStorage Class -- RegisterRegister

main( )

{

register int i ;

for ( i = 1 ; i


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Storage ClassStorage Class -- StaticStatic

Static variable persists between different function calls, whereas auto variable

reinitialized to 1 every time the function is called.


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Storage ClassStorage Class -- ExternalExternalint i ;main( )

{

printf ( "\ni = %d", i ) ;

increment( ) ;

increment( ) ;

decrement( ) ;

decrement( ) ;}

increment( )

{

i = i + 1 ;

printf ( "\n on incrementing i = %d", i ) ;

}

decrement( ){

i = i - 1 ;

printf ( "\n on decrementing i = %d", i ) ;

}

i = 0

onincre

menti

ng i =

1

on

incrementi


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Storage ClassesStorage Classes--When and whereWhen and where

to useto use

Economise the memory space consumed

by variables

Improve the speed of execution ofprograms

Static-only if want the value to persist

between different function calls

Register-only for those variables which are

being used frequently in the program


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Storage ClassesStorage Classes--When and whereWhen and where

to useto use

Extern-Only for those variables which are

being used by almost all the functions in

the program.

Auto-If dont have any of the needs

specified above, then go for auto.


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Hierarchy of OperationsHierarchy of Operations

Priority or precedence in which operations in

arithmetic statements are performed.

Within parenthesis hierarchy is same.But,if there is more than one set ofparenthesis, innermost parenthesis would be performed first.


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Determine hierarchy and evaluate the

following expression

i = 2 * 3 / 4 + 4 / 4 + 8 - 2 + 5 / 8

i = 6 / 4 + 4 / 4 + 8 - 2 + 5/ 8 operation: *

i = 1 + 4 / 4 + 8 - 2 + 5 / 8 operation: /

i = 1 + 1+ 8 - 2 + 5 / 8 operation: /

i = 1 + 1 + 8 - 2 + 0 operation: /

i = 2 + 8 - 2 + 0 operation: +

i = 10 - 2 + 0 operation: +i = 8 + 0 operation : -

i = 8 operation: +


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Evaluate

kk = 3 / 2 * 4 + 3 / 8 + 3

kk = 1 * 4 + 3 / 8 + 3 operation: /kk = 4 + 3 / 8 + 3 operation: *

kk = 4 + 0 + 3 operation: /

kk = 4 + 3 operation: +kk = 7 operation: +


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Converting general arithmeticConverting general arithmetic

statement to C statementstatement to C statement


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Associativity of operatorsAssociativity of operators

When an expression contains two operators of equal

priority, then it is solved using Associativity.

It can be of two types.

Left to Right

- Left operand must be unambiguous

Right to Left

- Right operand must be unambiguous


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Consider the expression

a = 3 / 2 * 5 ; /* there is a tie between *

and / operator */


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Consider one more expression

a = b = 3 ; /* both = has the same priority*/


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Another expression

z = a * b + c / d ; /* / and * has same priority

and same Associativity */


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P3_DataTypesAndStorageClassInC

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