Computer systems

What is hardware?

Physical components of a computer (e.g., CPU, memory, screen, keyboard)

What is software?

Programs and data that run on the hardware

What is the relationship between hardware and software?

Software instructs hardware; hardware executes software operations

Give an example of hardware.

Processor, RAM, motherboard, hard drive

Give an example of software.

Operating system, word processor, web browser

What is an operating system (OS)?

System software managing hardware and user interface

Name three functions of an OS.

Manage files, control hardware, manage user interface/memory

What is a utility program?

Software aiding management of computer resources (e.g., antivirus, backup, disk cleanup)

What are the main levels of programming languages?

Low-level and high-level languages

What is machine code?

Binary instructions run directly by CPU, specific to processor

What is assembly language?

Low-level code using mnemonics, one step above machine code

What is a high-level language?

Code similar to human language, easy for programmers to write/read (e.g., Python, Java)

Why use high-level languages?

Easier to write, read, debug, portable across platforms

What is a program translator?

Software converting code from one language to another so CPU can run it

Name three types of translator.

Assembler, compiler, interpreter

What does an assembler do?

Transforms assembly language into machine code

What does a compiler do?

Translates high-level code into machine code before running

What does an interpreter do?

Executes high-level code line by line

When is an interpreter used?

Testing/debugging, when immediate feedback is needed

When is a compiler used?

Producing fast executable files for users

State one advantage of low-level programming.

Close control of hardware, efficient use of resources

State one disadvantage of low-level programming.

Difficult to write, debug, and maintain

Which is easier to debug: high-level or low-level code?

High-level code

What is main memory?

Memory directly used by CPU for active programs/data (RAM, ROM)

What is RAM?

Random Access Memory; temporary, volatile storage used for active processes

What is ROM?

Read Only Memory; permanent, non-volatile, stores boot-up instructions

What does volatile mean?

Contents lost when power off (e.g., RAM)

What does non-volatile mean?

Contents retained when power off (e.g., ROM, hard drive)

What is secondary storage?

Non-volatile storage not directly accessed by CPU (e.g., hard disk, SSD)

Why is secondary storage needed?

To store programs/files permanently, retain data when off

What are two types of secondary storage?

Solid state (SSD), magnetic (hard disk)

How does solid state storage work?

Uses electrical circuits to store data persistently

State one advantage of SSD.

Fast, durable, silent, low power consumption

State one disadvantage of SSD.

More expensive than hard disk for same capacity

How does magnetic storage work?

Stores data by magnetising regions on a disk (hard drive, tape)

State one advantage of magnetic storage.

Cheap per GB, large capacities

State one disadvantage of magnetic storage.

Slower, prone to damage, noisy

What is cloud storage?

Data stored at remote location via Internet, using magnetic/solid state storage

Give an advantage of cloud storage.

Access from anywhere, backup, scalable

Give a disadvantage of cloud storage.

Needs Internet, possible security risks, ongoing cost

What is an embedded system?

Computer system built into another device for a dedicated function

Give two examples of embedded systems.

Car engine control, smart watch, washing machine controller

What is a non-embedded system?

General-purpose computer (PC, laptop)

What is a logic gate?

Electronic circuit performs logical operations on one/more inputs

Name four logic gates for GCSE.

NOT, AND, OR, XOR

What does NOT gate do?

Outputs opposite of input

What does AND gate do?

Outputs 1 only if both inputs are 1

What does OR gate do?

Outputs 1 if at least one input is 1

What does XOR gate do?

Outputs 1 if inputs are different

What is a truth table?

Table showing output of logic gate/circuit for all combinations of inputs

What is the Boolean expression for AND?

A AND B

What is the Boolean expression for OR?

A OR B

What is the Boolean expression for NOT?

NOT A

What is the Boolean expression for XOR?

A XOR B

Create the Boolean expression for a circuit with A AND (NOT B).

A AND (NOT B)

Create a logic circuit from Boolean expression (A OR B) AND C.

Input A and B to OR gate, output and input C to AND gate

What are standard logic circuit symbols used in GCSE?

Shapes for NOT (triangle with circle), AND (D-shape), OR (curved face), XOR (same as OR with extra curve)

Can truth tables use up to three inputs for GCSE?

Yes

What is a bus in computer systems?

Collection of wires transmitting data/signals between components

What is the central processing unit (CPU)?

Component performing calculations, executing instructions

Name three major CPU components.

Arithmetic logic unit (ALU), control unit (CU), registers

What does the ALU do?

Performs mathematical and logical operations

What does the control unit (CU) do?

Manages execution of instructions, data flow

What is the fetch-execute cycle?

CPU fetches, decodes, and executes instructions from memory

List the steps of the fetch-execute cycle.

Fetch instruction, decode, execute, repeat

How does main memory affect CPU performance?

Higher RAM = more/faster data available for processing

How do CPU clock speed, cores, cache affect performance?

Higher speed/cores/cache improve tasks done per second

What is machine code expressed in?

Binary, specific to each processor type

What makes code portable?

Can run on different hardware without altering code

What is software utility function?

Enhances computer performance, security, or maintenance

How does the OS handle multitasking?

Manages running of multiple processes/programs at once

How does the OS handle user management?

Handles logins, permissions, user accounts

What is a file system?

System OS uses to organise, store and retrieve files

Why is embedded system different from PC?

Single/few functions, less resources, no full OS

Give a benefit of embedded systems in devices.

Cheap, reliable, small, energy efficient

How do you construct a truth table for (A OR B) AND C?

List all input combinations, apply gates stepwise

How is secondary storage different than main memory?

Main memory is directly accessed by CPU, secondary is not

What does cloud storage rely on?

Internet connection to access remote servers

Why is ROM suitable for device firmware?

Permanent, doesn’t change when device is off

What role do logic gates play in computers?

Basic building blocks for all digital circuits, processors

Explain difference between assembler, compiler, interpreter.

Assembler: assembly to machine code; compiler: high-level to machine code all at once; interpreter: line-by-line execution

Which is faster: compiled or interpreted code?

Compiled code (once compiled, execution is quicker)

What is the function of registers in CPU?

Very fast, small memory locations for immediate data/instructions

What is a cache?

Fast memory storing frequently used data/instructions close to CPU

When is magnetic storage preferable?

High capacity needed, lower cost per GB

When is solid state storage preferable?

Fast speed, durability, portable devices

Summarise an advantage of high-level languages.

Easy to learn, maintain, write programs efficiently

Summarise a disadvantage of high-level languages.

Must be translated, may run slower, less hardware control

How does OS manage memory?

Allocates RAM, swaps programs in/out, frees memory when done

Why must you interpret Boolean expressions for logic circuits?

Ensure circuit works as intended, understand system logic

Why are utility programs useful?

Help keep computer running efficiently, securely, cleanly

What is the use of cloud in backing up data?

Data remains secure, accessible if local hardware fails

Describe the difference between embedded and non-embedded systems.

Embedded: built-in, dedicated tasks; non-embedded/general: full PCs, laptops

What is the benefit of multiple CPU cores?

Can process more tasks at same time, speeds up multitasking