Computer Systems and CPU Components

Computer Systems

• Computer systems use a model of input, process, output, and storage.
• Data is processed by the Central Processing Unit (CPU).
• The CPU needs input data and other instructions from storage to process.
• Data is output in a usable form (e.g., displayed on a monitor).
• Processed data is stored for future use.

CPU Components

• The CPU includes the Control Unit (CU), Arithmetic Logic Unit (ALU), Memory Address Register (MAR), and Memory Data Register (MDR).
• The Control Unit manages CPU operations.
• It retrieves instructions from memory and controls their execution.
• The ALU performs arithmetic and logical calculations.
• The MAR holds the address of the memory location to be accessed.
• The MDR holds data to be transferred to or from memory.
• Registers are small storage locations that hold data and instructions in the CPU, usually a multiple of 8 bits.

Memory

• Primary memory (RAM) is directly accessible by the CPU.
• RAM is volatile (data is lost when power is off).
• Read-Only Memory (ROM) is non-volatile (data is retained even when power is off).
• ROM stores permanent instructions for computer startup.
• Computer systems use binary (0 and 1) to store data.

Types of Memory

• Static RAM (SRAM): Faster but more expensive than DRAM.
• Dynamic RAM (DRAM): A type of primary memory used in computer systems.

Caches

• A cache (L1, L2) is a smaller, faster type of RAM placed between primary memory and the processor.
• It stores frequently accessed data and instructions to speed up processing.

Computer Programs

• Programs are stored in primary memory as sequences of instructions in machine code.
• Instructions are fetched from memory, decoded, executed, and the results are stored.

Primary Memory

• The primary memory (RAM) is the only storage directly accessible by the CPU.
• Data must be copied from storage to RAM before it can be processed.
• RAM holds the data currently needed by the CPU.

Secondary Memory

• Secondary memory stores data that may not be needed immediately.
• Examples: hard drives, USB drives, CDs, DVDs.
• Secondary memory is non-volatile (data is retained when power is off).
• Needed for storing and retrieving large amounts of data or to store data that needs to be persistent.

Operating Systems (OS)

• The OS controls hardware resources and provides services for computer programs.
• The OS manages memory, peripherals, resources, multitasking, networking, disk access and security functions.

Software Applications

• Word Processors: Used for document creation and editing.
• Spreadsheets: Used for organizing and analyzing data.
• Database Management Systems (DBMS): Used for managing structured data.
• Web Browsers: Used to access and display web pages.
• Email: Used to send and receive electronic messages.
• Computer-Aided Design (CAD): Used for creating and modifying design models.
• Applications: Software applications designed to meet user needs and interact with computer hardware using the operating system in between.

Computer System Architecture

• The CPU, RAM, and secondary storage (hard drives) are all involved in a computer system
• Secondary memory is needed to store programs and data that are not actively being used, and is accessed by the applications and the operating system.
• An OS manages how the applications use the memory.
• Using secondary and primary memory together is called virtual memory. Without virtual memory, applications may not run due to limited primary memory capacity.

Input/Output (I/O)

• I/O devices interact with the computer.
• Example: Keyboard, mouse, mouse.
• Peripheral devices are external devices or components.

Command Line Interface and GUIs

• Older systems use command-line interfaces.
• Modern systems use graphical user interfaces (GUIs).
• GUIs use icons, menus, and pointers for interaction.