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1. Central Processing Unit (CPU) Architecture and Functions

• Components of the CPU:

  • Microprocessor: Contains the Arithmetic Logic Unit (ALU) and Control Unit (CU).

  • ALU: Handles arithmetic operations (e.g., addition, subtraction) and logical comparisons (e.g., AND, OR).

  • CU: Decodes instructions and sends commands to various units within the system (e.g., directing signals between the ALU, memory, and input/output devices).

  • Registers: Temporary storage areas within the CPU used to hold data, instructions, and intermediate results during program execution.

• Buses:

  • Control Bus: Dictates the direction of data transfer.

  • Data Bus: Transfers data between components (e.g., ALU, RAM, I/O devices).

  • Address Bus: Sends address data from the microprocessor to primary memory.

2. Primary Memory

• Definition:

  • Primary memory is volatile and stores program instructions and data in machine code.

  • Known as RAM (Random Access Memory), it is fast but loses data when the computer is turned off.

3. Cache Memory

• Definition:

  • A smaller, faster, and more expensive section of RAM that stores frequently accessed data to improve performance.

  • Faster access speeds up the processor’s operation.

4. Machine Instruction Cycle

• Steps:

  • Fetch: Retrieve instructions from memory (Immediate Access Store - IAS).

  • Decode: Interpret the instruction in the Control Unit (CU).

  • Execute: Perform the operation (e.g., arithmetic or logic) in the ALU.

  • Store: Save the result in memory.

  • Repeat: Process continues with the next instruction.

5. Persistent Storage

• Definition:

  • When the system runs out of primary memory (RAM), data is moved to secondary storage (persistent storage) for safekeeping.

  • Ensures data is preserved when the system is powered off (e.g., hard drives, SSDs).

6. Main Functions of an Operating System

• Resource Management: Allocates and manages hardware resources.

• Memory Management: Controls access to memory and ensures processes don't interfere with each other.

• Error Handling: Detects and resolves system errors.

• I/O Handling: Manages input/output devices.

• Security & Protection: Prevents unauthorized access and provides secure execution of programs.

• Job Control Language (JCL) & Job Sequencing: Defines and prioritizes system jobs.

• User Interface: Provides an interface between the user and the computer system.

7. Application Software

• Functions:

  • Manages file maintenance, backups, formatting, archiving, data compression, virus checking, and disk defragmentation.

  • Enhances security and usability, ensuring smooth system performance.

8. Common Features of Applications

• File maintenance, backups, media formatting, archiving, and data compression are common features across various applications.

9. Data Representation in Computers

• Binary: Base-2 system (using digits 0 and 1).

• Bit: The smallest unit of data (0 or 1).

• Byte: A group of 8 bits.

• Denary/Decimal: Base-10 numerical system.

• Hexadecimal: Base-16 numerical system, commonly used in computing to represent binary data.

10. Boolean Operators

• AND: True if all inputs are true (1 AND 1 = 1, else false).

• OR: True if at least one input is true (0 OR 1 = 1).

• NOT: Inverts the value (NOT 1 = 0, NOT 0 = 1).

• NAND: NOT of AND (opposite of AND logic).

• NOR: NOT of OR (opposite of OR logic).

• XOR: True if inputs are different (1 XOR 0 = 1, 1 XOR 1 = 0).

11. Data/Instruction Flow Through the CPU

• Data Transfer:

  • Data is moved between registers, ALU, memory, and I/O devices via buses.

  • Data Bus: Transfers data in both directions.

  • Control Bus: Determines the direction of transfer.

  • Address Bus: Sends addresses from the CPU to memory.

12. Definitions

• Primary Memory: Volatile memory that stores data currently being used by the CPU (RAM).

• Cache Memory: A smaller, faster memory used to store frequently accessed data to increase processing speed.

• Machine Instruction Cycle: A sequence of steps (Fetch, Decode, Execute, Store) to execute machine language instructions.

13. Operating System Functions

• Controls essential system activities like resource allocation, error handling, security, and I/O management.

14. Software for New Computer Users

• Operating Software: Handles fundamental system functions (e.g., managing data, memory, I/O operations).

• Utility Software: Assists with tasks such as file maintenance, virus scanning, and data backup.

15. Data Representation Other Than Numbers

• Text Data: Represented using ASCII or Unicode encoding, where each character corresponds to a binary code.

• Graphics: Represented by pixel data, stored as bits.

16. Microprocessor Overview

• Microprocessor: The CPU of a computer, handling all data processing tasks.

• Components:

  • ALU: Performs arithmetic and logical operations.

  • CU: Decodes and controls program instructions.

  • Bus: A collection of wires for transferring data between CPU components and memory.

• CISC vs. RISC:

  • CISC (Complex Instruction Set Computing): More instructions, but slower execution.

  • RISC (Reduced Instruction Set Computing): Fewer instructions, faster execution.

• Pentium Microprocessor: Can handle 64 bits (compared to 32-bit older CPUs) and is optimized for both integers and floating-point numbers.