ITPEC IP April 2023 Question 2
Topic: Computer Component
Which of the following is the appropriate meaning of the units that are shown in the specifications given in brochures or catalogs?
Explanation
A 2-Tbyte hard disk holds 2 trillion bytes — catalogue specifications use the decimal SI prefixes, so tera means 1012, and each unit keeps its exact meaning.
- •T (tera) is 1012: a 2-Tbyte hard disk holds 2 × 1012 bytes. Disk makers count in powers of ten, which is why an OS counting in powers of two shows a smaller figure
- •dpi is dots per inch, a count along one inch of length
- •G (giga) is 109: 3.3 GHz is 3.3 × 109 Hz
- •k (kilo) in bps is 103: 56 kbps is 56 × 103 bits/second, the maximum rate
Answer (a)
Why not others:
- •(b) — dpi counts dots per inch (1 inch = 2.54 cm) along a line, not dots per square centimetre
- •(c) — 220 is about a million, a binary mega; 3.3 GHz is 3.3 × 109 Hz, about a thousand times more
- •(d) — 56 kbps is 56,000 bits/second, ten times 5.6 × 210 (about 5,734), and it is the maximum speed, not a minimum
Key rule: In specifications k, M, G and T are powers of ten, 103, 106, 109, 1012; binary multiples such as 210 and 220 are written Ki and Mi and appear mainly in memory sizes.
Computer Component · AI-written, may contain errors
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