A1.1 Computer Science Vocabulary

CPU

The CPU (Central Processing Unit) is the "brain" of a computer, acting as the primary computational engine. It processes data only by following instructions and coordinates data movement within the system.

Hardware

Physical devices that can be touched.

Software

Programs and applications that run on hardware (word, google docs, utilities)

Input devices

Devices that convert user actions into data the computer can process.

Output Devices

Devices that present processed information in human readable form.

Algorithmic Design

Creating step by step procedures to solve problems.

Decomposition

Breaking a complex problem into a manageable sub-problem.

Pattern Recognition

Pattern recognition refers to teaching computers to identify patterns or regularities in data automatically.

Arithmetic Logic Unit (ALU)

The ALU executes basic arithmetic (addition, subtraction) and logical operations (AND, OR, NOT). The CU supplies the data and the operation code.

Control Unit (CU)

Manages instruction sequencing, fetching each instruction from primary memory, decoding it and directing the ALU and registers.

Registers

Ultra-fast storage inside the CPU, hold data or address while the CPU is currently working.

Instruction Register (IR)

Holds the current instruction being executed.

Program Counter (PC)

Stores the address of the next instruction to be executed.

Memory Address Register (MAR)

Holds the memory address that is currently being fetched.

Memory Data Register

Holds the content of the data that has been fetched or is about to the written to the memory address.

Accumulator

Holds the results from the operations done by the ALU

Bus

Transfer data between various devices including the CPU, memory, storage and peripherals.

Control bus

Transfer commands and signals from the CPU to other components of the system. It is bidirectional. Examples: Read/write operations, interrupt requests, clock signals.

Data Bus

Carries data being processed between the CPU, memory and other peripherals. Width of the bus is important to determine the amount of data being transferred. 8,26,32 and 64 bits. Bidirectional.

Address Bus

Used to transmit the address that is to be read from or written to in memory.

Single Core Processors

The CPU has a single processor, which means it can only handle one task at a time.

Single Core Processor Key Ideas

Included in older devices.

Can have more than one application open, but CPU has to be shared between it and can impact the overall performance.

Multi-Core Processors

Two or more cores that can run multiple instructions simultaneously. Significantly faster than a single core processor.

Co-processor

Specific processor that has a specific task for the CPU, helper that speeds up specific tasks in the CPU.

GPU (Graphics processing unit)

renders images, animation, and video for the monitor (video games) by performing mathematical calculations.

Primary Memory

Stores the data and instructions that the CPU needs in order to process tasks.

RAM (Random Access Memory)

Volatile~ holds instructions and data of programs that are currently running.

Volatile

Losses its contents when the power to the computer is turned off.

ROM (Read only memory)

Non-volatile~ storing instructions that are very rarely modified. Cannot easily change its data. BIOS

Cache

Provides high-speed access to the CPU than the RAM. Holds the current instruction/data being used if going to the RAM is harder or slower.

Caches types

There are three types L1,L2 AND L3 with different sizes and speeds. The closer to the CPU, the faster it is.

L1 Cache

Located on the CPU, fastest type of cache. It is the smallest and each CPU component has its own L1 cache split between two sections, L1i to store instructions and L1d to store data.

L2 Cache

Located on top or situated very close to the CPU. More storage that can be used to store for frequently used instructions. Faster than L3 but slower than L1.

L3 Cache

Furthest from the CPU chip, may be shared on multiple-core CPUs, largest of the three. Slowest of the three.

Cache hit

Where the CPU requests data and is found in the cache memory.

Cache miss

When data is not found in memory leading to the retrieval from the slower main memory (RAM).

Fetch-decode-execute cycle

Instruction cycle, the fundamental process that a CPU uses to execute instruction from the memory.

Fetch

The CPU fetches an instruction from the memory.

Decode

CPU interprets the instruction and prepares the necessary operations to execute it.

Execute

CPU performs the actions required by the instruction.

Pipelining

Splits instruction into multiple stages, allowing multiple instructions to be ran simultaneously. The output of one stage becomes in the input of the next.

Memory access

Any necessary data is read from or written to memory

Write back

The result is written back to the CPU register

Independent Execution

tasks that don't rely on each other rather can be done alone and simultaneously.

Parallel execution

Where a computer runs multiple tasks or instructions instead of running one after another.

Internal storage

Hard disk drive (HDD) and solid-state drive (SSD). HDD: older tech, still often used, utilize a spinning magnetic disk to read/write data. SSD: use flash memory to store data, offering high-speed data access and durability.

eMMC (Embedded MultiMediaCard)

Flash storage that utilizes NAND flash memory. Their performance is adequate for basic computing needs and simple applications. (Internal)

Compression

Process of using fewer bits than the original representation.

Lossless Compression

No data is destroyed, original data can be perfectly reconstructed.

Lossy compression

reduces files by permanently eliminating certain information.

External storage

Portable versions of internal, CD, DVD, USB, SD, dedicated storage device accessed over a network.

Run Length Encoding (RLE)

Effective lossless data-compression technique used to reduce the size of files containing many consecutive repeated characters.

Transform Coding

A form of lossy compression often used in JPEG image compression or MP3 audio compression.

Software as a Service (SaaS)

delivers software applications over the internet. Allows users to access their software from anywhere as long as they have internet connection.

PaaS (Platform as a Service)

allows developers to build, test and deploy applications without managing the underlying infrastructure. Allows coders to focus on coding rather than the infrastructure management.

IaaS (Infrastructure as a Service)

users gain full control of computers, storage, network and the user can use however they want.