AQA 7517 · A-Level Computer Science · ~13 min read
Hardware vs Software
Hardware refers to any physical, tangible component of a computer system — the parts you can physically touch. Software refers to programs: sets of instructions that control hardware and enable users to perform tasks.
Feature
Hardware
Software
Physical?
Yes — tangible
No — intangible (data/instructions)
Examples
CPU, RAM, hard drive, keyboard
Operating system, browser, Word
Manufactured?
Yes — built/fabricated
No — written/coded
Can it wear out?
Yes — physical degradation
No — but can become obsolete
Categories of Software
System Software
Software that manages and controls the hardware, providing a platform for application software to run. Users rarely interact with it directly.
Operating System (OS) — manages resources, provides user interface, handles processes (e.g. Windows, Linux, macOS)
Device drivers — software that allows the OS to communicate with specific hardware devices (e.g. printer driver, graphics driver)
Utilities — programs that perform specific system maintenance tasks (e.g. disk defragmenter, antivirus, backup software)
Middleware — software that connects applications to services or databases
Application Software
Software designed for end-users to perform specific tasks.
General purpose — works across many uses (e.g. word processor, spreadsheet, web browser)
Special purpose — designed for one specific task (e.g. payroll software, photo editor)
Bespoke / custom — written specifically for a client's unique requirements
The Role of the Operating System
The OS is the most important piece of system software. Its functions include:
Process management — scheduling which processes run and when (CPU scheduling)
Memory management — allocating and deallocating RAM; virtual memory
File management — organising files and directories; permissions
Device management — coordinating input/output via device drivers
User interface — CLI (command line) or GUI (graphical)
Network management — handling network connections and protocols
Open Source vs Proprietary Software
Feature
Open Source
Proprietary
Source code
Publicly available — anyone can view, modify, distribute
Kept secret — only the vendor can modify
Cost
Usually free
Usually requires purchase/subscription
Examples
Linux, LibreOffice, Firefox, Python
Windows, Microsoft Office, Adobe Photoshop
Support
Community support (variable quality)
Official vendor support
Customisable?
Yes — freely modified
No — cannot change the code
Translators
Programs that convert source code into machine code that the CPU can execute:
Compiler — translates entire source program to machine code in one pass, before execution. Produces an executable file. Fast at runtime. E.g. C, C++
Interpreter — translates and executes line by line at runtime. No separate executable. Slower but easier to debug. E.g. Python, JavaScript
Assembler — converts assembly language (mnemonics) to machine code
Exam tip: Know the distinction between system software and application software, and be able to classify examples. Know all OS functions — AQA often asks for specific functions with explanations. Know open source vs proprietary trade-offs. Know compiler vs interpreter differences — AQA asks this frequently.
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Worksheet — 4.6.1 Hardware & Software
8 questions · instantly marked · AQA 7517 standard
Q1Distinguish between hardware and software. Give two examples of each.[4]
✅ Mark scheme
Mark scheme
Hardware: physical/tangible components of a computer system [1]; two examples e.g. CPU, RAM, hard drive, keyboard, monitor [1]. Software: programs / sets of instructions that control hardware or perform tasks [1]; two examples e.g. operating system, word processor, web browser, antivirus [1].
Q2State four functions of an operating system.[4]
✅ Mark scheme
Mark scheme
Any four of: process management / CPU scheduling [1]; memory management / allocation of RAM [1]; file management / organising files and directories [1]; device management / managing input-output via drivers [1]; providing a user interface (CLI/GUI) [1]; security / authentication / access control [1]; network management [1]. (1 mark each, max 4.)
Q3Explain the difference between general-purpose and special-purpose application software. Give one example of each.[4]
✅ Mark scheme
Mark scheme
General purpose: can be used for a wide variety of tasks [1]; example: word processor, spreadsheet, web browser [1]. Special purpose: designed for a single specific task [1]; example: payroll software, photo editing software, accounting software [1].
Q4Compare open source and proprietary software under the headings: source code access, cost, and support.[3]
✅ Mark scheme
Mark scheme
Source code: open source — freely available, can be viewed/modified/distributed; proprietary — kept secret, cannot be modified [1]. Cost: open source — usually free; proprietary — usually requires purchase or subscription [1]. Support: open source — community support (variable quality); proprietary — official vendor support (guaranteed but may be costly) [1].
Q5Explain how a compiler differs from an interpreter. State one advantage of each.[4]
✅ Mark scheme
Mark scheme
Compiler: translates entire source program to machine code before execution [1]; advantage: fast execution at runtime / produces distributable executable [1]. Interpreter: translates and executes one line at a time during runtime [1]; advantage: easier to debug / no compilation step needed during development [1].
Q6What is a device driver and why is it needed?[2]
✅ Mark scheme
Mark scheme
A device driver is software that allows the operating system to communicate with a specific hardware device [1]; each device has different specifications — the driver translates OS commands into the device-specific instructions the hardware understands [1].
Q7A school is considering open source software for all computers. Describe two advantages and one disadvantage of this decision.[3]
✅ Mark scheme
Mark scheme
Advantages (any two): no licence cost — saves money [1]; source code can be customised for school-specific needs [1]; large community means bugs are quickly identified and fixed [1]. Disadvantage: community support may be inconsistent / no guaranteed vendor support [1]; could require technical expertise to configure/maintain [1].
Q8Classify each of the following as system software or application software, and justify your answer: (a) Antivirus software, (b) Spreadsheet program, (c) Printer driver.[3]
✅ Mark scheme
Mark scheme
(a) Antivirus — system software (utility): maintains the system and protects the hardware/OS from threats [1]. (b) Spreadsheet — application software (general purpose): used directly by end-users for a specific productivity task [1]. (c) Printer driver — system software: allows the OS to communicate with the printer hardware [1].
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Mini Test — Hardware & Software
10 questions · 10 minutes
⏱ 10:00
Section A — Multiple Choice [5 marks]
Q1Which of the following is system software?
Q2A compiler differs from an interpreter in that it:
Q3Open source software:
Q4A device driver is:
Q5Which is an example of bespoke software?
Section B — Short Answer [5 marks]
Q6State one function of the OS memory management module.
Mark schemeAllocates and deallocates RAM to processes as needed / manages virtual memory [1].
Q7Give one advantage of using an interpreter during software development.
Mark schemeEasier to debug — errors reported line by line during execution / no separate compilation step [1].
Q8Why is Linux considered open source?
Mark schemeIts source code is publicly available — anyone can view, modify, and redistribute it freely [1].
Q9What does an assembler do?
Mark schemeConverts assembly language (mnemonics) into machine code that the CPU can execute directly [1].
Q10State one disadvantage of proprietary software.
Mark schemeSource code cannot be modified / usually requires purchase licence / vendor lock-in [1].