Enforcement Officer / Accounts Officer (EO/AO) 2020 recruitment test, advertisement 421. Transcribed from the Commission's own booklet (series A, NMJX-U-GTA); 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 represents 1 GB of information ?

(a)1024 KB
(b)1024 MB
(c)1024 TB
(d)1024 PB

Answer

Why

Correct — B, (b) 1024 MB.

Computer storage is measured in a ladder of units in which each step is 1024 times the one below it, because 1024 is 2 raised to the tenth power and machines count in binary. Reading the ladder upward from the byte:

1 kilobyte (KB) = 1024 bytes 1 megabyte (MB) = 1024 KB 1 gigabyte (GB) = 1024 MB 1 terabyte (TB) = 1024 GB 1 petabyte (PB) = 1024 TB 1 exabyte (EB) = 1024 PB

A gigabyte therefore sits one step above the megabyte, and 1024 MB is exactly 1 GB. In bytes it works out to 1024 × 1024 × 1024, that is 1,073,741,824 bytes, or 2 to the thirtieth power.

The item is testing whether a candidate knows the ORDER of the units as well as the multiplier, because every option uses the same number, 1024, and differs only in which unit it is applied to. That is a deliberate design: a candidate who remembers ‘1024’ and nothing else has no way to choose. What decides the answer is knowing which unit stands immediately below the gigabyte, and the sequence to hold in memory is byte, kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte — each one 1024 of the last.

A useful check when the ladder slips: 1024 of a unit always makes ONE of the next unit up. So 1024 KB makes 1 MB, 1024 MB makes 1 GB, 1024 GB makes 1 TB. Read that way, only one option can produce a gigabyte.

Why the others are wrong

(a)1024 KB — 1024 KB is one MEGABYTE, not a gigabyte — it falls one full step short. This is the most attractive wrong answer, and it catches two kinds of candidate. The first has memorised that the multiplier is 1024 but not the order of the units, and picks the option in which 1024 appears next to the smallest unit on the list. The second is thinking of the kilobyte as ‘the small one’ and the gigabyte as ‘the big one’ and assumes a single jump connects them. It takes two jumps: 1024 KB gives 1 MB, and another 1024 of those gives 1 GB. Expressed directly, 1 GB is 1,048,576 KB.
(c)1024 TB — 1024 TB is one PETABYTE, which is a thousand times larger than a terabyte and about a million times larger than a gigabyte. The error here is direction: the candidate has the ladder but has climbed it the wrong way, treating the gigabyte as though it stood above the terabyte. The correct relation runs the other way — 1024 GB make 1 TB, so a terabyte is bigger than a gigabyte, not smaller. A practical anchor helps: an ordinary laptop hard disk is measured in hundreds of gigabytes or a small number of terabytes, while petabytes are the scale of large data centres and national archives.
(d)1024 PB — 1024 PB is one EXABYTE, the step above the petabyte and far beyond anything a gigabyte could describe. Like option (c) this reverses the direction of the ladder, and it does so by two steps rather than one, so it is the least plausible of the four. It is included to complete the pattern: with the same numeral standing beside four different units, the option set becomes a direct test of whether the candidate can place the units in order. Reading the ladder from the bottom — kilo, mega, giga, tera, peta, exa — rules this option out at once, since the exabyte is the largest unit named on the paper and the gigabyte the second smallest.

Concept

A computer stores everything as bits. A BIT is a single binary digit, 0 or 1, and it is the smallest unit of information. Eight bits make a BYTE, which is the unit in which storage is actually counted, because a byte is roughly what one character of text occupies in the older encodings. Four bits are sometimes called a nibble, and the group of bits a processor handles at once is its word — 32 bits or 64 bits on ordinary machines.

Above the byte the units climb in steps of 1024, and the reason is binary arithmetic: 2 to the tenth power is 1024, which is close enough to a thousand for the metric prefixes kilo, mega, giga and tera to have been borrowed for them. So 1 KB is 2^10 bytes, 1 MB is 2^20, 1 GB is 2^30, 1 TB is 2^40, 1 PB is 2^50 and 1 EB is 2^60. Beyond the exabyte the ladder continues with the zettabyte and the yottabyte.

There is a genuine ambiguity in this vocabulary that is worth knowing about, though it does not affect this question. Manufacturers of disks and network equipment often use the metric prefixes in their strict decimal sense, where a gigabyte is 1,000,000,000 bytes, while operating systems report storage in the binary units of 1024. That is why a disk sold as 1 TB shows as roughly 931 GB once installed. To remove the confusion, the International Electrotechnical Commission introduced a separate set of names for the binary units — kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB) — in which 1024 MiB is 1 GiB. Indian competitive examinations, including this paper, use the traditional convention in which the binary step of 1024 is called a kilobyte, megabyte or gigabyte, and that is the convention the question is set in.

A feel for scale is worth building alongside the arithmetic. A page of plain text is a few kilobytes. A photograph from a phone camera is a few megabytes. An hour of video is a few gigabytes. The storage of a large organisation runs to terabytes, and the traffic of a national network to petabytes.

This item belongs to the computers block of Part B, which on this paper runs in two runs of five questions and covers memory, hardware, software, networking and file formats. Units of storage are the block’s most predictable topic, because they can be tested in one line with four short options and no diagram.

The design of the option set is what makes the item worth studying. All four options carry the same number, so the number itself is not the answer — the unit is. That shape recurs across this block, and across the quantitative section too: when every option shares a component, the shared part is never what is being tested, and the candidate should look immediately at what differs. Here what differs is the unit, so the question is really asking ‘which unit sits immediately below the gigabyte’.

The habit worth carrying forward is to write the ladder down in the margin at the start of any such question — B, KB, MB, GB, TB, PB — rather than trying to hold it in the head while reading four similar options. Two seconds of writing removes the direction error that produces options (c) and (d).

Key facts

1 byte = 8 bits; a bit is a single binary digit, 0 or 1.
Each step of the storage ladder is 1024 times the one below, because 1024 = 2^10.
1 KB = 1024 bytes; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB; 1 PB = 1024 TB; 1 EB = 1024 PB.
1 GB = 1,073,741,824 bytes = 2^30 bytes = 1,048,576 KB.
The order of units from small to large: byte, kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte, yottabyte.
4 bits are a nibble; the group of bits a processor handles at once is its word, commonly 32 or 64 bits.
Disk manufacturers often use the decimal sense of the prefixes, where 1 GB is 1,000,000,000 bytes, which is why a disk sold as 1 TB is reported by the operating system as about 931 GB.
The IEC names for the strictly binary units are kibibyte, mebibyte and gibibyte, written KiB, MiB and GiB, where 1024 MiB = 1 GiB.

Every option uses 1024 — what decides it is which unit sits below the gigabyte

1 byte = 8 bits→A bit is a single binary digit, 0 or 1, and the smallest unit of information. Four bits are a nibble; the group of bits a processor handles at once is its word, commonly 32 or 64 bits.

The ladder, each step 1024 times the last→1 KB = 1024 bytes. 1 MB = 1024 KB. 1 GB = 1024 MB. 1 TB = 1024 GB. 1 PB = 1024 TB. 1 EB = 1024 PB. The multiplier is 1024 because 2^10 = 1024, which is close enough to a thousand for the metric prefixes kilo, mega, giga and tera to have been borrowed for them.

1 GB = 1024 MB→In bytes that is 1024 × 1024 × 1024 = 1,073,741,824, or 2^30.

The check to use when the ladder slips→1024 of a unit always makes ONE of the next unit up. So 1024 KB makes 1 MB — option (a) falls a full step short. Read that way, only one option on the page can produce a gigabyte.

The two options that climb the wrong way→1024 TB is one PETABYTE and 1024 PB is one EXABYTE. Both treat the gigabyte as though it stood above the terabyte, when the relation runs the other way: 1024 GB make 1 TB.

The real ambiguity behind these units→Disk and network manufacturers often use the prefixes in their strict decimal sense, where a gigabyte is 1,000,000,000 bytes, while operating systems report storage in binary units of 1024 — which is why a disk sold as 1 TB shows as roughly 931 GB once installed. The IEC names for the strictly binary units are kibibyte, mebibyte and gibibyte, written KiB, MiB and GiB.

Study next

Number systems: binary, octal, decimal and hexadecimal, and conversion between them.The memory hierarchy — registers, cache, RAM, secondary storage — and how speed, cost and capacity trade off along it.Primary against secondary memory, and volatile against non-volatile storage.Character encodings: ASCII, extended ASCII and Unicode, and how many bytes each character costs.Storage devices and their typical capacities: hard disk, solid-state drive, optical disc, flash drive, magnetic tape.Data-transfer rates, which are measured in bits per second rather than bytes — Kbps, Mbps, Gbps — and why an 8 Mbps connection does not download 8 MB in a second.

Common traps

Remembering the multiplier 1024 but not the order of the units. Every option here uses 1024, so the multiplier alone decides nothing.
Climbing the ladder in the wrong direction and treating the gigabyte as larger than the terabyte or the petabyte.
Jumping two steps at once — assuming that kilobytes convert to gigabytes in a single multiplication by 1024.
Confusing bits with bytes. A byte is eight bits, and network speeds quoted in Mbps are in bits, not bytes.
Using 1000 instead of 1024 when a question asks for an exact figure in bytes. Indian competitive examinations set these items on the binary convention.

Units of storage appear on EPFO EO/AO papers in three shapes. The first is this one — which quantity equals one unit, with the same numeral placed beside four different units. The second asks for a conversion in the other direction, such as how many kilobytes make a gigabyte. The third asks for the smallest or largest unit in a list, or for the correct ascending order of a jumbled set. All three are answered by the same single piece of knowledge: the ordered ladder and the step of 1024. Related items in the same block ask for the number of bits in a byte, or for a binary-to-decimal conversion, which is why the powers of two up to 1024 are worth knowing by sight.

Related PYQs

EPFO_EOAO_2020_Q26Open & attempt →

What is the equivalent decimal value of binary number 101110 ?

(a) 46
(b) 56
(c) 64
(d) 65

Answer(a) 46

The other item in this computer block that rests on binary arithmetic — converting a binary number to decimal — and the reason the powers of two up to 1024 are worth knowing by sight.

EPFO_EOAO_2020_Q28Open & attempt →

Which one of the following memories is extremely fast and acts as a high-speed buffer between the CPU and the main memory ?

(a) RAM
(b) ROM
(c) Flash Memory
(d) Cache Memory

Answer(d) Cache Memory

A memory item from the same block, on the fast buffer between the processor and main memory; the memory hierarchy is where the units measured here are actually applied.

Practice

practice — not a real PYQ
Which one of the following arranges the units of computer storage in ascending order of size ?
- (a)KB, MB, TB, GB
- (b)MB, KB, GB, TB
- (c)KB, MB, GB, TB
- (d)GB, MB, KB, TB
Answer(c) KB, MB, GB, TB — the ladder runs kilobyte, megabyte, gigabyte, terabyte, with each unit 1024 times the one before it.
practice — not a real PYQ
How many kilobytes make one gigabyte ?
- (a)1024
- (b)1,048,576
- (c)1,073,741,824
- (d)10,24,000
Answer(b) 1,048,576 — a gigabyte is 1024 megabytes and each megabyte is 1024 kilobytes, so 1024 × 1024 = 1,048,576 KB. The figure 1,073,741,824 in option (c) is the number of BYTES in a gigabyte, not the number of kilobytes.

Why