Enforcement Officer / Accounts Officer (EO/AO) 2017 recruitment test. Transcribed from the Commission's own booklet (series A, GRS-A-TNS); answer as per the official UPSC final answer key. This question is in Part B. Answer last reviewed 24 August 2026.

Which one of the following is hardware?

(a)Power point
(b)Control unit
(c)Printer driver
(d)Operating system

Answer

Why

Correct — B, (b) Control unit. Hardware is the physical part of a computer system — anything that can be touched, unplugged or replaced — while software is the set of instructions that runs on it. Of the four options only one names a physical component, and it is the control unit.

The control unit is one of the two working parts of the central processing unit, the other being the arithmetic and logic unit. It is circuitry etched on the processor chip, and its job is to run the instruction cycle: fetch the next instruction from memory, decode it to find out what operation it specifies, and then issue the timing and control signals that make the rest of the machine carry it out — telling the arithmetic and logic unit which operation to perform, telling memory whether to read or write, telling the registers when to accept a value. It directs; it does not calculate. Because it is part of the processor rather than a separate box on the desk, candidates sometimes hesitate over whether it is a real component at all, and that hesitation is what the option is testing.

The other three options are all software, and between them they cover both of software's kinds. A presentation program is application software, written for a user's task. A printer driver and an operating system are system software, written to run and manage the machine itself. Sorting the four by that single test — is this a thing or a set of instructions — settles the item without any further knowledge.

Why the others are wrong

(a)Power point — Printed here as two words, this is the presentation program — application software, a set of instructions supplied on a disc or downloaded, installed on to a machine and capable of being uninstalled again without a screwdriver. Nothing about it is physical. The distinction that matters is between the program and the medium that carries it: the disc a program arrives on is hardware, and so is the drive that holds the disc and the memory the program is loaded into, but the program itself is not. Application software is the layer a user actually works in — the word processor, the spreadsheet, the presentation package, the browser — and it sits on top of the operating system, which in turn sits on the hardware. A candidate who sorts the four options into that three-layer picture finds only one of them in the bottom layer.
(c)Printer driver — A printer driver is software, even though the thing it drives is hardware, and this is the most instructive of the three wrong options because the confusion it exploits is a real one. The printer on the desk is a physical device; the driver is the small piece of system software that lets the operating system talk to that particular model, translating a general instruction to print a page into the specific sequence of commands and data the device expects. Change the printer and the driver must be changed too, which is why every new device comes with one. The rule to carry away is that anything ending in the word driver is a program: a device driver is the software counterpart of a device, not the device itself, and it is installed and removed like any other program.
(d)Operating system — An operating system is the largest and most important piece of system software on the machine — the collection of programs that starts when the machine is switched on, manages the processor, the memory, the storage and the attached devices, and provides the environment in which application software runs. It allocates memory to programs, schedules their turns on the processor, organises files into directories and mediates every request a program makes for a device. All of that is management of hardware, which is exactly why the option is tempting: an operating system is defined by its relationship with hardware without ever being hardware. It arrives as files, it can be replaced with a different one on the same machine, and the same machine can hold two of them at once — none of which is true of a physical component.

Concept

A computer system is understood as three layers. At the bottom is hardware, everything physical: the processor with its control unit, arithmetic and logic unit and registers; main memory; secondary storage; and the input and output devices attached to the machine. In the middle is system software, which exists to run the machine — the operating system, the device drivers, the utilities, and the translators such as compilers and interpreters that turn a programmer's source into instructions the processor understands. At the top is application software, written for the user's own purpose: word processing, spreadsheets, presentation, accounting, browsing. Between the first two layers sits firmware, which is software recorded permanently in a chip, and it is the only case where the distinction has to be stated carefully: the chip is hardware, the instructions in it are software. Within the hardware layer the processor deserves its own picture, because it is where this question points. The control unit fetches and decodes instructions and generates the signals that carry them out; the arithmetic and logic unit performs the calculations and comparisons; the registers hold the values being worked on and the addresses being used. All three are circuitry on one chip.

The hardware-and-software question is the most reliable regular of the EPFO computer block, and it is asked in the same way every time: four names are offered, one is a component and three are programs, or the reverse. It is asked because the distinction is the minimum a non-specialist officer needs in order to read a purchase note, a maintenance contract or an audit observation correctly, and because a candidate who cannot make it will also misread everything else in the block. The examiner's craft lies in choosing software whose names sound physical — a driver, a system, a unit — and in choosing hardware that is inside another component rather than sitting visibly on the desk. The control unit is exactly that kind of hardware: nobody has ever seen one on its own, because it is a region of the processor chip. The test that survives all of this is the simplest one available: could this be picked up, and would replacing it require opening the machine, or only running an installer?

Key facts

Hardware is the physical equipment of a computer system; software is the set of instructions that runs on it.
The central processing unit contains the control unit, the arithmetic and logic unit and a set of registers, all of them circuitry on the chip.
The control unit fetches and decodes each instruction and issues the control signals that make the rest of the machine execute it; it does not itself calculate.
The arithmetic and logic unit performs the arithmetic and the comparisons, which is the work the control unit directs.
System software runs the machine — the operating system, device drivers, utilities and language translators.
Application software serves the user's own task — word processing, spreadsheets, presentation packages, browsers and accounting programs.
A device driver is software that lets the operating system communicate with one particular model of attached device; the device is hardware, the driver is not.
Firmware is the borderline case: instructions recorded permanently in a chip, so the chip is hardware and the instructions in it are software.

One test settles it — is this a thing, or a set of instructions?

(b) Control unit — hardware→One of the two working parts of the central processing unit, the other being the arithmetic and logic unit. It is circuitry etched on the processor chip: it fetches the next instruction from memory, decodes it to find what operation it specifies, and issues the timing and control signals that make the rest of the machine carry it out. It directs; it does not calculate.

Why candidates hesitate over it→Because it is part of the processor rather than a separate box on the desk, it does not look like a component at all — and that hesitation is exactly what the option is testing.

(d) Operating system — system software→The largest and most important program on the machine: it starts when the machine is switched on, allocates memory to programs, schedules their turns on the processor, organises files and mediates every request a program makes for a device. All of that is management of hardware, which is why it tempts — it is defined by its relationship with hardware without ever being hardware.

(c) Printer driver — system software→The most instructive of the three, because the confusion it exploits is real. The printer on the desk is a physical device; the driver is the small program that lets the operating system talk to that particular model. Anything ending in the word driver is a program — the software counterpart of a device, not the device itself.

(a) Power point — application software→A presentation program: a set of instructions supplied on a disc or downloaded, installed on to a machine and capable of being uninstalled again without a screwdriver. The distinction that matters is between the program and the medium carrying it — the disc is hardware, so is the drive and so is the memory it loads into; the program is not.

The three layers, and the borderline case→Hardware at the bottom. System software in the middle, existing to run the machine — the operating system, device drivers, utilities, and the translators that turn source into instructions. Application software at the top, serving the user's own task. Firmware is the one case needing care: instructions recorded permanently in a chip, so the chip is hardware and the instructions in it are software.

Study next

The parts of the central processing unit and what each contributes to the instruction cycleSystem software against application software, with the operating system's own functions listedThe fetch, decode and execute cycle, and the registers that support itDevice drivers, the plug-and-play mechanism and how an operating system recognises new equipmentFirmware, the BIOS or UEFI, and what happens between switching a machine on and the operating system loading

Common traps

Assuming that anything to do with a physical device is hardware; a printer driver is software about hardware.
Reading the word unit as though it meant a separate box, when the control unit is a region of the processor chip.
Classifying the operating system as hardware because it manages hardware and starts before anything else.
Forgetting that a program's medium and the program are different things — the disc is hardware, the software on it is not.
Overlooking firmware when the distinction is stated too rigidly; the chip is hardware and the instructions inside it are software.

This item belongs to the most predictable family in the EPFO computer block. The examiner offers a mixed list and asks which member is hardware, which is software, which is system software or which is an application, and the wrong options are chosen for the plausibility of their names rather than for any technical subtlety. The related family asks what a named part of the processor does — which register keeps track of the next instruction, which register holds the address about to be accessed, what the arithmetic and logic unit is for — and both families are answered from one labelled diagram of the machine. Draw the three layers once, put the processor's own parts inside the bottom layer, place half a dozen familiar names on the diagram, and the whole family becomes recall rather than reasoning.

Related PYQs

EPFO_EOAO_2020_Q68

Which one of the following registers is used to keep track of the next instruction to be executed ?

(a) Memory address register
(b) Memory buffer register
(c) Program counter
(d) Memory data register

Answer(c) Program counter

Inside the processor, one level below this item: which register keeps track of the next instruction to be executed.

EPFO_APFC_2016_Q87

A collection of programs that controls how the computer system runs and processes information is called

(a) Compiler
(b) Operating System
(c) Linker
(d) Assembler

Answer(b) Operating System

The software side of the same distinction — what the collection of programs that controls how the computer runs is called.

Practice

practice — not a real PYQ
Which one of the following is a part of the central processing unit rather than a program running on the computer?
- (a)Device driver
- (b)Arithmetic and logic unit
- (c)Utility program
- (d)Compiler
Answer(b) Arithmetic and logic unit
practice — not a real PYQ
Which one of the following functions is performed by the control unit of a computer?
- (a)Performing arithmetic and logical operations on data
- (b)Holding data permanently after the power is switched off
- (c)Fetching and decoding instructions and issuing the signals that execute them
- (d)Converting a source program into machine language
Answer(c) Fetching and decoding instructions and issuing the signals that execute them

Why