Hardware means the physical parts you can touch. The software is the coded instructions that tell those parts what to do, and a computer needs both to work.
Neither part is any use on its own. Bare hardware just sits there until software gives it instructions, and software has nowhere to run without hardware to carry it out.
Keeping the split in mind helps diagnose faults: a problem is either a hardware fault (a part has failed) or a software fault (the instructions are wrong).
The Processor: The Computer's Brain
The central processing unit (CPU) carries out a program's instructions; often called the computer's brain, it does calculations and makes decisions, with the motherboard connecting it to everything else.
Inside are a control unit (picks the next instruction), an arithmetic-logic unit (does sums and comparisons), and registers (hold current values).
They repeat one endless loop: fetch, decode, execute. How fast and how many loops at once is much of what makes a computer powerful.
Memory and Storage
Memory and storage do different jobs. RAM is fast, temporary memory holding what the computer uses right now; it is volatile, so its contents vanish when power is cut.
Storage keeps data permanently even with the power off: a hard disk drive (spinning magnetic disks, cheap and roomy but slower) versus a solid-state drive (memory chips, faster and sturdier but costlier). RAM is your open document, storage is the saved file.
Smaller memories: read-only memory holds fixed start-up instructions, and a tiny ultra-fast cache keeps the CPU's most-used data close. The pattern is a trade-off of speed, cost, and whether data survives a power cut.
Everyday consequences: too little RAM slows a device when many apps run; full storage leaves nowhere to save. This is why many people use cloud storage, trading some control of their data for space they need not manage.
The user interface is the point of contact between person and machine: a graphical user interface (point at icons, intuitive) versus a command-line interface (typed commands, faster and precise for experts but less approachable).
A haptic interface communicates through touch, such as a phone buzz or a controller rumble. Because the interface is where people actually experience a computer, its design can decide whether someone finds the technology usable at all.
Software: Operating Systems and Applications
The operating system is core software that manages the hardware and shares it out (memory, storage, devices) and gives a consistent user interface. Windows, macOS, Android, and iOS are operating systems.
On top run applications, programs for specific tasks (browser, word processor, game). An application asks the operating system to handle the hardware rather than talking to it directly.
Software is a stack: app on operating system on hardware. This is why updating the OS can change every app's behaviour, and why a program written for one OS will not simply run on another.
Layering is why updates matter: they fix flaws including the security holes malware exploits, so an unpatched operating system leaves every app on it exposed.
When Software Turns Hostile
Malware is any program written with a hostile purpose: to steal data, spy on users, or damage systems.
Common kinds: viruses (spread between files), trojans (hide inside harmless-looking apps), and ransomware (locks files and demands payment).
Because computers are connected, malware can spread machine to machine and disrupt essential services that whole communities depend on. Disrupting those services can cut off hospitals, banks, or transport that people rely on.
Case study
Case study: CrowdStrike outage (2024)
System: CrowdStrike Falcon is security software that runs deep inside the Windows operating system (kernel level) on millions of business computers (computers and networks content topics).
Specifics: on 19 July 2024 a faulty update to Falcon crashed around 8.5 million Windows machines worldwide into repeated blue-screen failures, grounding flights and disrupting hospitals, banks, and broadcasters. It became the largest IT outage on record, and it was a defective update, not a cyberattack.
Impacts and implications: essential services stopped at once because they all ran the same low-level software, and recovery often needed a hands-on fix per machine; software sitting close to the hardware has enormous power over whether a computer runs at all, and leaning on one vendor turns its mistake into everyone's outage.
Concepts: systems (one update cascaded through interconnected machines), power (control of low-level software is control over the device), values and ethics (testing, resilience, accountability); economic and political contexts.
Theory of Knowledge
TOK
If free security updates exist but are not installed, where does responsibility for an attack lie?
When the same tool can protect or attack a system, what makes a piece of software malicious?
Active recall
Self review
What is the difference between hardware and software, and why does each need the other?
What does the CPU do, and what are the steps of its cycle?
How does RAM differ from storage, and what does volatile mean?
What is a user interface, and why does its design affect who can use a computer?
How do applications, the operating system, and hardware form a layered stack, and what is malware?
