Instruction codes and computer registers

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INSTRUCTION CODES AND COMPUTER REGISTERS Nikhil Gaba 8125

description

Sanjeev Patel 4x

Transcript of Instruction codes and computer registers

Page 1: Instruction codes and computer registers

INSTRUCTION CODESAND

COMPUTER REGISTERS

Nikhil Gaba

8125

Page 2: Instruction codes and computer registers

Instruction code An instruction code is a group of bits that

instruct the computer to perform a specific operation.

Two parts-

Operation code-specifies the operation

Address-specifies operands, registers or memory word

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Stored program organization

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Direct and Indirect address

When the second part of an instruction code specifies the actual operand instruction is said to have an immediate operand.

When the second part specifies the address of operand it is called direct address.

When the second part specifies the address of the memory word in which address of the operand is found is called indirect address.

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Basic computer registers

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Functions

DR-Holds memory operand AC-Processor register IR-Holds instruction code TR-Holds temporary data AR-Holds address for memory PC-Hold address of next instruction INPR-Holds input character OUTR-Holds output character

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