Hardware and software

Hardware is the physical components that make up a computer system — the parts that can be touched, such as the CPU, RAM and monitor (1).

Software is the programs and instructions that run on the hardware and tell it what to do, such as the operating system or a web browser (1). (2)

(a) Hardware — a physical memory chip (1) (b) Software — a program that performs a task for the user (1) (c) Software — a driver is a program that allows the operating system to communicate with a hardware device (1) (d) Hardware — a physical component (1) (4)

Software provides the instructions that tell the hardware what to do — without it, the hardware would have nothing to carry out and would sit idle, unable to do anything useful (1).

The hardware stores and executes the software — the instructions must be held in memory and carried out by a physical processor, so software cannot run without hardware to run on (1).

The two are therefore mutually dependent: a computer system needs both to function, since neither is of any use on its own (1). (3)

(a) It is software (1), because it is a set of instructions telling the machine what to do — the fact that it is stored on a physical chip does not change what it is (1).

(b) It is called firmware — software stored permanently on a hardware chip (1).

(c) The chip is hardware but the program stored on it is software, and distinguishing them matters practically: a fault in the program can be corrected by updating the firmware, whereas a fault in the chip itself would require physically replacing the component (1). (4)

All the hardware is present and correctly assembled, but hardware only executes instructions — it cannot decide for itself what to do (1). Software provides those instructions, and with none installed the CPU has nothing to fetch and execute, so the machine cannot perform any task (1).

In particular there is no operating system, so there is nothing to manage the hardware, provide a user interface, or allow any application to be loaded and run (1).

This demonstrates the relationship directly: the hardware is fully functional but useless without software to direct it, which is why both are required for a working computer system (1). (4)

(a) Hardware — a physical crack requires the screen to be replaced (1) (b) Software — a program crashing repeatedly indicates a bug, fixed by updating, patching or reinstalling the program (1) (c) Hardware — no response at all on power-up suggests a physical failure such as the power supply, requiring the component to be repaired or replaced (1) (d) Software — the printer's device driver is likely to be incompatible with the new operating system, fixed by installing an updated driver (1) (4)

The software approach has the advantage that it can be updated: if a new video format is released, the program is simply patched and the existing hardware continues to work (1). Its disadvantage is speed — the CPU is a general-purpose processor, so it must execute a large number of instructions to complete the task, making it slower and more power-hungry (1).

The hardware approach has the advantage of being much faster and more efficient, because the logic is built directly into a purpose-designed circuit rather than being carried out step by step in software (1). Its disadvantage is that it cannot be changed — supporting a new format would require physically replacing the chip (1).

The trade-off is therefore speed and efficiency against flexibility (1). A hardware implementation suits a task that is stable and performed very frequently, such as decoding a long-established format on a phone where battery life matters, whereas a software implementation suits a task likely to change, where being able to update matters more than raw speed (1). (6)

The program is software stored as a file on secondary storage, such as a hard disk or SSD, which is itself hardware (1). When the user double-clicks the icon, the operating system — also software — handles the request to run it (1).

The program's instructions are then loaded from secondary storage into main memory (RAM), because the CPU can only directly access main memory (1). The CPU then repeatedly fetches each instruction from main memory, decodes it to work out what it is, and executes it (1).

As those instructions are carried out, they control other hardware — sending output to the monitor and taking input from the keyboard, for example (1).

This illustrates the relationship precisely: the software is stored on, loaded into and executed by hardware, while at the same time directing what that hardware does (1). (6)

The statement is wrong because it confuses what something controls with what something is (1). Controlling hardware is precisely what software exists to do, so it cannot be the test for being hardware.

A device driver controls a hardware device such as a printer, yet it is a program — a set of instructions allowing the operating system to communicate with that device — so it is software (1).

Firmware likewise controls a device such as a washing machine and is stored on a physical chip, but the instructions stored on that chip are software (1). The chip is hardware and what is stored on it is software — they are two different things occupying the same place (1).

The correct test is whether the item is physical: if it can be touched it is hardware, and if it is a set of instructions or data it is software (1).

The confusion is understandable, because software is always stored on hardware and so is physically inseparable from it in practice — but the distinction is about the nature of the thing, not its location (1). (6)