Memory Units — Set 1

Correct Answer: A. Bit

• **Bit** = the most fundamental unit of data in computing, capable of holding exactly one binary value — either 0 or 1 — making it the atomic building block of all digital information. • **‘Bit’ is short for ‘Binary Digit’** — it represents the physical state of an electronic switch: high voltage = 1, low voltage = 0. • Computers use billions of bits in combination to store complex data like images, audio, and programs. • 💡 Option B (Byte) is wrong because a byte is 8 bits grouped together, not the smallest unit; Option C (Nibble) is wrong because a nibble is 4 bits; Option D (Kilobyte) is wrong because it equals 1024 bytes, which is far larger.

Correct Answer: D. 4 bits

• **Nibble** = exactly 4 bits grouped together, making it precisely half of one byte and the smallest named grouping larger than a single bit. • **A nibble represents one hexadecimal digit** — since hex uses values 0–F (0–15), and 4 bits can encode 2^4 = 16 unique values, the mapping is perfect. • Nibbles were commonly used in early BCD (Binary-Coded Decimal) systems to store one decimal digit per nibble. • 💡 Option A (2 bits) is wrong because 2 bits form a ‘crumb’, not a nibble; Option B (16 bits) is wrong because 16 bits form a ‘word’ in some architectures; Option C (8 bits) is wrong because 8 bits form a byte.

Correct Answer: A. Byte

• **Byte** = a group of 8 bits that serves as the universal standard unit for representing a single character, because 8 bits give 256 (2^8) possible values — enough to cover all letters, digits, and symbols in ASCII. • **Byte is the smallest addressable unit in most CPU architectures** — meaning the processor retrieves at minimum 1 byte at a time from memory, never a lone bit. • Character encodings like ASCII assign one byte per character; UTF-8 uses 1–4 bytes per character for broader language support. • 💡 Option B (Word) is wrong because word size varies by CPU (16/32/64 bits) and is not tied to character representation; Option C (Bit) is wrong because a single bit can only hold 0 or 1, not a character; Option D (Pixel) is wrong because a pixel is a display element, not a memory unit.

Correct Answer: D. 1024 bytes

• **1 Kilobyte (KB) = 1024 bytes** in binary computing, because computer memory uses powers of 2, and 2^10 = 1024 is the power of 2 closest to the decimal ‘kilo’ value of 1000. • **The gap between 1000 and 1024 matters** — operating systems and hardware manufacturers sometimes use 1000 bytes per KB (decimal), causing discrepancies in reported vs actual storage size. • The IEC introduced ‘Kibibyte (KiB)’ = 1024 bytes to eliminate this ambiguity, while reserving ‘Kilobyte’ for the decimal 1000-byte definition. • 💡 Option A (1000 bytes) is wrong because that is the SI/decimal definition, not the binary computing standard used in textbooks; Option B (512 bytes) is wrong because 512 = 2^9, which is half a kilobyte; Option C (1048 bytes) is wrong because there is no standard unit of this size.

Correct Answer: A. 1 Megabyte

• **1 Megabyte (MB) = 1024 Kilobytes**, following the binary hierarchy where each unit is exactly 2^10 times the previous one, making 1 MB approximately 1,048,576 bytes in total. • **Megabyte was the standard measure for early storage media** — a floppy disk held 1.44 MB, and early computers shipped with RAM measured in single-digit MB values. • The abbreviation MB (uppercase B) always refers to Megabytes; Mb (lowercase b) refers to Megabits, which is 8 times smaller. • 💡 Option B (1 Terabyte) is wrong because 1 TB = 1024 GB, which is enormous compared to 1024 KB; Option C (1 Gigabyte) is wrong because 1 GB = 1024 MB, not 1024 KB; Option D (1 Petabyte) is wrong because 1 PB = 1024 TB, far beyond 1024 KB.

Correct Answer: A. KB < MB < GB < TB

• **KB < MB < GB < TB** is the correct ascending order of memory units, with each step being exactly 1024 times larger than the previous one in the binary system. • **Each unit is 2^10 = 1024 times its predecessor** — KB to MB to GB to TB forms a clean exponential ladder used universally in computing hardware specifications. • Knowing this order is essential for comparing file sizes, RAM capacities, and storage drive specifications in everyday computing. • 💡 Option B (MB < KB < GB < TB) is wrong because KB is smaller than MB, not the other way around; Option C (GB < MB < KB < TB) is wrong because it reverses the first three units; Option D (TB < GB < MB < KB) is wrong because it lists the units in descending order.

Correct Answer: D. 1024 Megabytes

• **1 Gigabyte (GB) = 1024 Megabytes** in binary computing, which equals approximately 1,073,741,824 bytes (about one billion bytes in the decimal sense). • **Gigabyte is the everyday storage unit of modern devices** — smartphone storage, RAM, and USB drives are all commonly sold in GB capacities ranging from 4 GB to 512 GB. • The word ‘giga’ comes from the Greek ‘gigas’ meaning giant; in binary computing it represents 2^30 bytes. • 💡 Option A (1024 Kilobytes) is wrong because that equals only 1 MB, not 1 GB; Option B (2048 Megabytes) is wrong because 1 GB is 1024 MB, not 2048; Option C (1000 Terabytes) is wrong because 1000 TB would equal approximately 1 Exabyte.

Correct Answer: A. Petabyte

• **Petabyte (PB) = 1024 Terabytes**, a unit used to measure massive data collections in enterprise data centers, cloud platforms, and national-scale databases. • **Global internet traffic is measured in Petabytes per day** — major platforms like Facebook and Google collectively store data in the hundreds of Petabytes range. • One Petabyte can store approximately 13.3 years of HD video, or around 500 billion pages of standard text. • 💡 Option B (Exabyte) is wrong because 1 EB = 1024 PB, making it larger than 1024 TB; Option C (Zettabyte) is wrong because 1 ZB = 1024 EB, far beyond 1024 TB; Option D (Yottabyte) is wrong because it is the largest standard unit, equal to 1024 ZB.

Correct Answer: D. The fixed number of bits processed by the CPU at once

• **Word** = the fixed number of bits that a CPU can process in a single operation, determined entirely by the processor’s architecture — 16-bit, 32-bit, or 64-bit systems each have different word sizes. • **Word size directly sets the CPU’s power and memory limit** — a 32-bit CPU can address at most 4 GB of RAM (2^32), while a 64-bit CPU can theoretically address 16 exabytes. • All arithmetic, logic, and data-movement operations inside a CPU are performed on data chunks of exactly one word at a time. • 💡 Option A (The size of a text file) is wrong because file size is measured in bytes and has nothing to do with CPU architecture; Option B (A string of characters) is wrong because that is a software concept, not a hardware unit; Option C (The length of a password) is wrong because password length is a security concept unrelated to CPU word size.

Correct Answer: A. Terabit

• **Terabit (Tb)** uses a lowercase ‘b’ because in standard notation, lowercase ‘b’ always means bit while uppercase ‘B’ means byte — so Tb = Terabit and TB = Terabyte, two very different quantities. • **Terabits are used for network speed, not storage** — high-speed fiber optic backbone links are rated in Tb/s (Terabits per second), whereas storage drives are measured in TB (Terabytes). • 1 Terabit = 1024 Gigabits = 0.125 Terabytes, since there are 8 bits in every byte. • 💡 Option B (Terabyte) is wrong because TB uses uppercase ‘B’; Option C (Tetrabyte) is wrong because no such standard unit exists; Option D (Tetrabit) is wrong because this term does not exist in computing standards.