Computer Organization and Networks Overview

These flashcards cover key vocabulary from the topics of computer organization and networks taught in the IB Computer Science syllabus.

ALU

Arithmetic Logic Unit; the internal component of the CPU that executes mathematical calculations (e.g., addition, subtraction) and logical comparisons (e.g., checking if x > y or performing $AND$/$OR$ operations).

CU

Control Unit; the "brain" of the CPU that directs the flow of data, decodes instructions from memory, and coordinates the timing and actions of all other computer components.

Registers

Extremely fast, small storage locations situated within the CPU itself. They are used to hold data currently being processed or instructions that are currently being executed.

MAR

Memory Address Register; a specific register that holds the memory address ($RAM$ location) of the next data item or instruction to be fetched from or stored into memory.

MDR

Memory Data Register; a register that acts as a buffer, holding the actual data or instruction that has just been read from memory or is about to be written to a memory address.

Buses

Physical communication channels (sets of wires) that transfer data, memory addresses, and control signals between the CPU, memory, and input/output devices.

Von Neumann Architecture

A foundational computer design where the CPU is separate from the memory, and both program instructions and data are stored in a single shared memory space, using the same buses.

Machine Instruction Cycle

The four-step process (Fetch, Decode, Execute, Store) that the CPU repeats continuously for every instruction to process programs.

Fetch

The first stage of the cycle where the Control Unit (CU) retrieves an instruction from the memory address stored in the program counter and moves it into the internal registers.

Decode

The stage where the CU interprets the binary machine code of a fetched instruction to determine which operation is required and which hardware components are needed for execution.

Execute

The stage where the CPU carries out the command. This often involves calculation by the ALU or moving data between different hardware components.

Store

The final stage of the instruction cycle where the results of the execution are written back into a register or a specific memory location for long-term use.

RAM

Random Access Memory; the primary volatile storage of a computer. It holds the OS, active applications, and current data. It is much faster than secondary storage but loses all data when power is disconnected.

ROM

Read Only Memory; non-volatile memory containing the "firmware" or start-up instructions (bootstrap) required to boot the computer. It cannot be easily altered or erased.

Cache Memory

A high-speed, volatile memory located on or very near the CPU chip. It stores copies of frequently accessed data from RAM to reduce the time the CPU spends waiting for data.

Virtual Memory

A memory management technique that uses a portion of the secondary storage (hard drive) as an extension of RAM. It allows larger programs to run but significantly slows down performance due to disk access speeds.

Operating System

The core software that manages interactions between the user, application software, and computer hardware resources like memory, processors, and storage.

Application Software

Programs designed for end-users to perform specific tasks, such as word processing, web browsing, or accounting, as opposed to system software which runs the computer.

Bit

The smallest unit of data in computing, representing a logical state with one of two possible values: $0$ (off) or $1$ (on).

ASCII

American Standard Code for Information Interchange; a character set standard that assigns unique numeric values to letters, digits, and symbols to represent text in computers.

Binary

A base-$2$ numeral system using digits $0$ and $1$. It is the fundamental language of computers because it aligns with the two states of electronic transistors.

Hexadecimal

A base-$16$ numeral system using digits $0-9$ and letters $A-F$. It is used as a human-friendly shorthand for binary, where one hexadecimal digit represents exactly $4$ bits.

Network Types

Classifications of networks based on size:

• LAN (Local Area Network): Private network over a small area (e.g., home/office) with high speeds.

• WAN (Wide Area Network): Connects LANs over large distances (e.g., the Internet), typically slower and managed by third parties.

VPN

Virtual Private Network; a secure connection that encrypts data traffic over a public network.

• Pros: Enhances privacy, secures data on public Wi-Fi, and bypasses regional content restrictions.

• Cons: Can decrease internet speed, depends on provider trustworthiness, and may be blocked by some services.

OSI Model

Open Systems Interconnection; a conceptual framework of $7$ layers (Physical, Data Link, Network, Transport, Session, Presentation, Application) that standardizes networking functions for cross-platform compatibility.

Encryption

The process of using mathematical algorithms and keys to convert readable data (plaintext) into an unreadable format (ciphertext) to prevent unauthorized access.

MAC Address

Media Access Control; a unique, physical identifier hard-coded into a Network Interface Controller (NIC) used to identify a device on a local network segment.

Data Packet

A standardized unit of data transmitted over a network. It contains a header (source/destination IP), a payload (the actual data), and a trailer (for error checking).

Packet Switching

A method of data transmission where messages are broken into packets that travel independently through the network and are reassembled at the destination, maximizing bandwidth efficiency.

Twisted Pair

A common copper cabling where pairs of wires are twisted together to minimize electromagnetic interference and cross-talk between cables.

Fibre Optic

A high-performance transmission technology using light pulses through glass fibers. It offers the highest speeds, greatest bandwidth, and total immunity to electromagnetic interference.

Wireless Networking

The connection of devices using radio waves or infrared signals instead of physical cables, providing high mobility but often lower security and speed compared to wired solutions.