Computer Systems, Hardware, Software & CPU Architecture Basics

Computer System

A set of hardware and software working together to take input, process it, and produce an output.

Hardware

The physical, tangible components of a computer system that you can touch, such as the CPU, motherboard, or SSD.

Software

The non-physical sets of instructions (programs) that tell the hardware what to do.

General-Purpose System

A computer designed to perform a wide variety of tasks by installing different software (e.g., PCs, tablets).

Dedicated (Embedded) System

A computer built into a larger device to perform one specific, fixed task (e.g., a microwave or car engine control unit).

IPOS Model

The fundamental operational cycle of a computer: Input (taking data), Process (CPU calculations), Output (presenting results), and Storage (holding data for later).

Stored Program Concept

The revolutionary idea (central to Von Neumann Architecture) that both program instructions and data are stored together in the same main memory (RAM).

CPU (Central Processing Unit)

The 'brain' of the computer that processes instructions and data.

Fetch-Decode-Execute (FDE) Cycle

The continuous loop the CPU follows to process data.

Fetch

Retrieves the next instruction from RAM.

Decode

The Control Unit interprets what the instruction means.

Execute

The CPU carries out the required action, such as a calculation or logic operation.

ALU (Arithmetic Logic Unit)

Performs all mathematical calculations (+, -, *, /) and logical comparisons (AND, OR, NOT,

Control Unit (CU)

Acts as the 'conductor' of the CPU, managing instruction execution and sending control signals to coordinate the FDE cycle.

Registers

Tiny, extremely fast storage locations directly inside the CPU used for specific tasks during the FDE cycle.

Program Counter (PC)

Holds the memory address of the next instruction to be fetched.

Memory Address Register (MAR)

Holds the memory address of the current instruction or data being accessed.

Memory Data Register (MDR)

Holds the actual data or instruction just fetched from or about to be written to memory.

Accumulator (ACC)

Stores the immediate results of calculations performed by the ALU.

Cache Memory

High-speed memory inside the CPU that stores frequently used instructions to reduce the time spent fetching from the slower RAM.

Clock Speed

Measured in Hertz (Hz), this represents the number of FDE cycles a CPU can perform per second (e.g., 3.0 GHz = 3 billion cycles/sec).

Core

An independent processing unit within a CPU.

Buses

Physical sets of wires used to transfer data between components.

Address Bus

Carries the location of data from the CPU to RAM.

Data Bus

Carries the actual data/instructions between the CPU and RAM.

Control Bus

Carries command signals from the Control Unit.

Primary Memory

Memory directly accessible by the CPU, consisting of RAM and ROM.

RAM (Random Access Memory)

Volatile memory that acts as the CPU's 'worktable,' holding the OS, open applications, and active data.

ROM (Read Only Memory)

Non-volatile memory that contains the 'start-up' instructions (BIOS/Bootstrap loader) required to boot the computer.

Volatility

Refers to whether memory loses its data when power is turned off.

Virtual Memory

An extension of RAM using a portion of secondary storage (HDD/SSD).

Secondary Storage

Non-volatile, long-term storage used for files and programs when not in use.

Persistence

The ability of a storage device to retain data permanently even without power.

Latency

The time delay before a component begins the transfer of data.

Storage Units

Data is measured using the '1,000 rule' (Decimal/Base-10).

Bit (b)

A single 0 or 1.

Byte (B)

8 bits.

Kilobyte (KB)

1,000 bytes.

Megabyte (MB)

1,000 KB.

Gigabyte (GB)

1,000 MB.

Terabyte (TB)

1,000 GB.

Machine Code

The only language a CPU understands, consisting of binary (0s and 1s).

High-Level Language

Human-readable languages (like Python) that are portable but must be translated.

Low-Level Language

Languages like Assembly that use mnemonics and have a near 1-to-1 mapping with machine instructions.

Source Code

The original program code written by a programmer.

Object Code

The translated version of the source code produced by a compiler.

Translators

Tools that convert source code into machine code.

Assembler

Translates Assembly language into machine code.

Compiler

Translates the entire source code into a standalone Executable File (.exe) all at once.

Interpreter

Translates and executes code line-by-line at runtime.