🖥️ CENTRAL PROCESSING UNIT (CPU) – Complete Notes

(Home Academy  | Exam-Oriented for JKSSB, SSC, Bank, UGC NET)

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1. Meaning of CPU

The Central Processing Unit (CPU) is known as the brain of the computer. It performs all the instructions of a program by processing data and controlling all the components of the computer.

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2. Parts of CPU

1. ALU (Arithmetic Logic Unit) – Performs all arithmetic operations (addition, subtraction, multiplication, division) and logical operations (comparisons like greater than, less than, equal to).

2. CU (Control Unit) – Directs all operations of the computer. It fetches instructions from memory, decodes them, and manages execution by coordinating with ALU, memory, and input/output devices.

3. Registers – Small, high-speed storage units inside CPU used to hold temporary data, instructions, and intermediate results during processing. Common registers include Program Counter (PC), Instruction Register (IR), and Accumulator.

4. Cache Memory – High-speed memory inside CPU used to store frequently accessed data and instructions to speed up processing.

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3. Functions of CPU

1. Fetch – Retrieves instructions from the computer’s memory (RAM).

2. Decode – Interprets the instruction and converts it into signals the computer can execute.

3. Execute – Performs arithmetic, logic, or data transfer operations as instructed.

4. Store/Write Back – Sends the processed data back to memory or output devices.

5. Control Operations – Directs and coordinates all other components of the computer system.

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4. Key Points for Exams

• CPU is the brain of the computer responsible for processing instructions.

• ALU performs arithmetic and logical operations.

• CU manages instruction flow and device coordination.

• Registers and cache improve speed and efficiency of the CPU.

• CPU interacts with memory, input, and output devices to perform tasks.

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📘 MCQs – CPU

1. What is the CPU known as?
   A) Memory of computer
   B) Brain of computer
   C) Storage unit
   D) Input device
   Answer: B) Brain of computer

2. Which part of the CPU performs arithmetic operations?
   A) Control Unit
   B) Registers
   C) Arithmetic Logic Unit
   D) Cache
   Answer: C) Arithmetic Logic Unit

3. What is the function of Control Unit (CU)?
   A) Perform arithmetic calculations
   B) Store data permanently
   C) Direct and manage all operations of the computer
   D) Display output
   Answer: C) Direct and manage all operations of the computer

4. Registers in CPU are used for:
   A) Permanent storage
   B) Holding temporary data and instructions
   C) Displaying results
   D) Input operations
   Answer: B) Holding temporary data and instructions

5. Cache memory is used to:
   A) Slow down processing
   B) Store frequently accessed data for faster processing
   C) Input data into computer
   D) Store permanent files
   Answer: B) Store frequently accessed data for faster processing

6. Which of the following is NOT a part of CPU?
   A) ALU
   B) CU
   C) Hard Disk
   D) Registers
   Answer: C) Hard Disk

7. CPU executes instructions in which sequence?
   A) Decode → Fetch → Execute → Store
   B) Fetch → Decode → Execute → Store
   C) Store → Execute → Fetch → Decode
   D) Execute → Fetch → Decode → Store
   Answer: B) Fetch → Decode → Execute → Store

8. The Program Counter (PC) is a type of:
   A) Cache
   B) Register
   C) Secondary memory
   D) Input device
   Answer: B) Register

9. CU controls operations by sending signals to:
   A) Only ALU
   B) Memory and input/output devices
   C) Keyboard only
   D) Hard disk only
   Answer: B) Memory and input/output devices

10. Which part of CPU performs logical operations like comparing numbers?
    A) Control Unit
    B) ALU
    C) Cache
    D) Registers
    Answer: B) ALU

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