Computer Programming Part 1-Programming and Computer Architecture-Lecture Slides, Slides of Computer Architecture and Organization

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Computer ProgrammingBitwise operators, Left shit, right shift, OR,

AND &

XOR operations

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Bitwise Operators^ ^ As their name suggests, the bitwiseoperators enable you to operate on aninteger variable at the bit level.^ ◦^ Can be applied to any type of integers:^ ^

Signed  Unsigned  However they are usually applied to unsignedinteger types.

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Example^ unsigned int number =163870;unsigned int result= number <<2;^ ^ The left operand of the shift operator is the value to beshifted^ ^ While the number of bit positions that the value is tobe shifted is specified by the right operand.

4

Decimal 16,387 in binary :^0

Shift left 2:

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Example (Contd.)

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Similarly if we apply shift right:Shift right 2:

unsigned int number =163870;unsigned int result= number >> 2;

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Shifting Signed Integers^ ^ As mentioned earlier bitwise shift operatorscan be applied to both signed and unsignedintegers.^ ^ Right shift

on signed integer types can vary between different systems and it depends onyour compiler.  In some cases it will fill

‘0’^ bits at the left to

fill in the vacated bit positions.  In other cases the sign bit is propagated tothe right so

‘1’^ bit fills the vacated bit positions.

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Shifting Signed Integers( Contd.)^ ^ The reason for propagating the sign bit,where this occurs, is to maintainconsistency between a right shift and adivide operation.^ ^ We will illustrate this with a variable oftype

char

, just to show how it works.

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Logical Operations on Bit Patterns Operator

Description

-^

Bitwise complement operator.

This is a unary operator that

will invert the bits to its operand so 1 becomes 0 and 0becomes 1. &^

Bitwise AND operator which will AND the correspondingbits in its operands. If corresponding bits are both 1 thenresulting bit is 1, otherwise it is 0. ^^

Bitwise exclusive OR operator (XOR) if corresponding bitsare different e.g. 1 and 0 result will be 1 otherwise if bits aresame e.g. 0 and 0 result will be 0. |^

Bitwise OR operator. If corresponding bits are 0 and 0 theresulting bit will be 0, otherwise it is 1.

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AND^ ^ One major use of AND operation is forplacing 0s in one part of a bit patternwhile not disturbing the other part.^ ^ For example 00001111^ ◦^ without knowing the second operand we cansay that the first four most significant bits willbe 0s^ ◦^ Moreover the four least significant bits will bea copy of the second operand.

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AND(Contd.)^ ^ This use of the AND operation is called^ masking

. ^ Here one operand, called the

mask

,

determines which part of the otheroperand will affect the result.  In case of AND operation, maskingproduces a result that is a partial replicaof the one operand, with 0s occupying thenonduplicated positions.

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AND(Contd.)^ ^ Such an operation is useful whenmanipulating a

bit map

,

◦^ A string of bits in which each bit representsthe presence or absence of a particular object ◦^ We have encountered bit maps in context ofrepresenting images, where each bit isassociated with a pixel.

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OR(Contd.)

(^11110000) OR 10101010^11111010

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XOR^ ^ A major use of XOR operation is in theforming of complement of a bit string^ ^ XORing any byte with a mask of all 1sproduces the complement of the byte.

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Quiz 61-Describe basics of a typical C++ environment .2- What two kinds of files hold you code in C++?3- Define types of scope variables with the help ofexample?4- What are Precedence? Write the Precedence table.5- Write code in C++ to explain the working of constvariable.6- Write a program that will display students gradesfrom A-F.7- Describe the difference between assignment andequality operator with help of examples.

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