Computer Science O'Clock Unit 1

### Review Guide

#### Definitions and Descriptions

1. Hardware: The physical components of a computer, such as the motherboard, CPU, RAM, and hard drive.

2. Software: Programs and applications that run on the computer, like operating systems (Windows) and browsers (Chrome).

3. Peripheral: External devices that communicate with the computer, like a mouse, keyboard, or printer.

4. Human Resources: People involved in managing and using technology and processes in a business or economy.

5. CPU (Central Processing Unit): The brain of the computer, responsible for executing instructions.

6. CU (Control Unit): Part of the CPU that manages the execution of instructions by directing other components.

7. ALU (Arithmetic Logic Unit): The part of the CPU that handles arithmetic and logic operations.

8. MAR (Memory Address Register): Holds the memory address of data that needs to be accessed by the CPU.

9. MDR (Memory Data Register): Temporarily holds data that is being transferred to or from memory.

10. Input, Process, Storage, Output Model: A conceptual model where data is inputted, processed, stored, and then outputted by a system.

11. Address Bus: A communication system that transfers the location (address) of data in memory.

12. Data Bus: Transfers actual data between the CPU and memory.

13. RAM (Random Access Memory): Volatile memory used for temporary storage while programs are running.

14. SRAM (Static RAM): Fast, expensive memory used in caches, doesn't need constant refreshing.

15. DRAM (Dynamic RAM): Slower, cheaper main memory that needs to be constantly refreshed.

16. ROM (Read Only Memory): Non-volatile memory that stores essential startup instructions for the computer.

17. Cache memory: Very fast memory that stores frequently accessed data for quick retrieval by the CPU.

18. L1 / L2 / L3 Cache: Levels of cache memory. L1 is the fastest and smallest, closest to the CPU. L2 and L3 are progressively larger and slower.

19. Primary Memory: Memory that is directly accessible by the CPU, like RAM and ROM.

20. Secondary Memory: Non-volatile memory, such as hard drives and SSDs, used for long-term storage.

21. Machine Instruction Cycle: The process the CPU follows to execute an instruction, involving fetch, decode, execute, and store steps.

22. Fetch: The CPU retrieves an instruction from memory.

23. Decode: The CPU interprets the instruction.

24. Execute: The CPU performs the instruction.

25. Store: The CPU writes the result back to memory.

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#### Roles of Key Components

1. CU (Control Unit): Manages and coordinates the CPU’s activities by fetching and decoding instructions.

2. ALU (Arithmetic Logic Unit): Performs arithmetic operations and logical comparisons.

3. MDR (Memory Data Register): Temporarily stores data that is being read from or written to memory.

4. MAR (Memory Address Register): Stores the address of the data or instruction that needs to be accessed.

5. Data Bus: Transfers data between the CPU and memory.

6. Address Bus: Transfers the location of the data being accessed, not the data itself.

7. Cache: Stores frequently accessed data so the CPU can retrieve it more quickly than from main memory.

8. RAM: Temporary storage for currently running programs and processes; provides fast access to data.

9. Secondary Memory: Long-term storage for data and programs; slower but non-volatile.

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#### Comparisons

1. RAM vs. ROM:

- RAM: Volatile memory, used for temporary storage while programs are running. Data is lost when the computer is turned off.

- ROM: Non-volatile memory, used for permanent storage of critical data like system startup instructions. Data remains even when the power is off.

2. Cache vs. DRAM vs. Secondary Memory:

- Cache: Fastest memory, used to store frequently accessed data.

- DRAM: Slower than cache, but faster than secondary memory; used as main memory.

- Secondary Memory: Slowest, used for long-term storage.

3. Address Bus vs. Data Bus:

- Address Bus: Carries the location of the data in memory.

- Data Bus: Carries the actual data between the CPU and memory.

4. MDR vs. MAR:

- MDR: Holds the actual data being transferred.

- MAR: Holds the address of where the data is located in memory.