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CENTRAL PROCESSING UNIT
(CPU)
P R E PA R E D B Y
P R A B I N M A H A R J A N
B I M 1 S T S E M E S T E R
S E C T I O N “ B ”3/24/2015 1
CONTENTS:
 I N T R O D U C T I O N O F C P U
 F U N C T I O N O F C P U
 C O M P O N E N T S O F T H E C P U
 FA C TO R S A F F E C T I N G P R O C E S S I N G S P E E D
 C P U C Y C L E
 C O N C L U S I O N
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INTRODUCTION
 It is a multipurpose, programmable, clock-driven, register based semiconductor
device
 CPU interprets instructions to the computer, performs the logical and arithmetic
processing operations, and causes the input and output operations
 First CPU was made in the 1940s and was ran with the first computer the
EDVAC
 It is made up of silicon chip which normally contains millions of transistors.
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FUNCTION OF CPU
 To carry out processing.
 To perform arithmetic calculation such as addition, subtraction.
 To read instruction & data from memory.
 To communicate with peripherals using system bus.
 To give commands to all parts of the computer system.
 To control the timing of information flow.
 To control the storage of data or instruction.
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COMPONENTS OF CPU
1. ALU (Arithmetic Logic Unit)
2. CU (Control Unit)
3. Register Array
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ALU (ARITHMETIC LOGIC UNIT)
 ALU performs arithmetic and logic operations such as addition,
subtraction, multiplication, division, shifting operations and logic
instructions
 ALU includes a group of register-high speed memory locations built
directly into the CPU that holds the data currently being processed
which is known as Accumulator
 ALU also perform operation like increment, decrement etc.
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CU (CONTROL UNIT)
 CU directs the moment of electronic signals between main memory and
ALU
 It acts as the nerve center of the computer system
 It provides the necessary timing and control signals to all the
operations in the computer
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REGISTER ARRAY
 Register is the special purpose temporary storage locations inside the
CPU that holds data that is being processed
 It generally occupy the top-most position in the memory hierarchy,
providing high-speed and fast access
 It is normally made of static or dynamic random access memory (RAM)
cells
 E.g.
• Accumulator
• Address Register
• Instruction register
• Sequence register
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FACTORS AFFECTING PROCESSING SPEED
 Clock rate of the CPU
 Computer word size
 Bus speed
 Main memory size
 Cache memory size
 Instruction set complexity
 Number of processing units
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CPU CYCLE
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FETCHING
EXECUTING
STORING DECODING
CONCLUSION
 Thus CPU is the main part (brain) of the computer system
 It controls the operation of all other components such as memory, input and
output device
 It interprets instructions to the computer, performs the logical and arithmetic
operations
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THANK YOU
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