UKPSC Prelims 2025 General Studies Paper-I · Question 8 of 149

Correct — C, Hertz.

A processor works to the beat of an internal clock, and its speed is the number of beats that clock completes in one second. Hertz is the SI unit of frequency, one hertz being one cycle per second, so a 2.4 GHz chip is one whose clock ticks about 2.4 billion times a second.

Carry away that the unit has to match the dimension of the quantity. Clock speed is a count of cycles per second, so it takes a frequency unit; the other three options measure amounts of data or parts of a picture, which are not rates.

• (a)
  Byte — A byte says how much data there is, not how fast anything happens. It is the standard unit for storage capacity and file size — a disk in gigabytes, a photograph in megabytes — and conventionally holds eight bits.

  Byte and hertz share the giga prefix: 8 GB of memory and 3 GHz of clock speed both read as "giga". The prefix only scales; the unit that follows it is what names the quantity.

• (b)
  Bit — A bit — short for binary digit — holds one of two values, 0 or 1. It is the right answer to the smallest unit in which data is represented, and eight of them make up a byte.

  The word does appear in processor specifications, as in a 64-bit processor. There it describes how wide a chunk of data the chip handles in one operation, which is a matter of capacity per step rather than of steps per second.

• (d)
  Pixel — A pixel, short for picture element, is the smallest addressable point of a digital image or screen. It is the right answer to how the resolution of a display or an image is expressed, as in 1920 × 1080.

  It belongs to the output side of the machine and describes how finely a picture is divided up. That is a spatial count, whereas the stem asks for a rate of working.

Choosing a unit is a matter of matching dimensions. Some quantities are amounts of stuff, some are counts of spatial elements, and some are rates — an amount divided by time. The unit must belong to the same category as the quantity.

A processor's clock speed is a rate: the number of cycles finished each second. The unit of one cycle per second is the hertz, so clock speed is quoted in megahertz or gigahertz.

• Hertz (Hz) is the SI unit of frequency; one hertz is one cycle per second.
• The unit is named after the German physicist Heinrich Hertz, who demonstrated electromagnetic waves experimentally.
• Processor clock speed is quoted in megahertz (10⁶ Hz) or gigahertz (10⁹ Hz); a 3 GHz clock completes about three billion cycles a second.
• A byte is the standard unit of digital storage and conventionally consists of 8 bits.
• A bit, short for binary digit, carries a single value of 0 or 1.
• A pixel, short for picture element, is the smallest addressable point of a digital image; resolution such as 1920 × 1080 counts pixels.
• Hertz also measures a monitor's refresh rate and the frequency of the domestic AC mains supply, which is 50 Hz in India.
• Clock speed counts cycles, not work finished; core count, cache and architecture also shape how a processor performs.

• Reading the prefix instead of the unit: 8 GB and 3 GHz both begin with giga, yet one is storage and the other is speed.
• Treating "64-bit processor" as a speed rating, when the bit-width describes how much data the chip handles in one operation.
• Confusing bits per second, which is a data transfer rate, with the bit itself, which is a static unit of data.
• Assuming a higher clock figure settles which processor is better, when core count, cache and architecture also decide performance.
• Tying hertz to processors alone and then missing it when the same unit is asked for a monitor's refresh rate or a wave's frequency.

• practice — not a real PYQ

  A processor clock speed of 1 gigahertz corresponds to how many clock cycles per second?

  • (a)One thousand
  • (b)One million
  • (c)One billion
  • (d)One trillion
  Answerc — The prefix giga stands for 10⁹, and one hertz is one cycle per second, so 1 GHz is one billion cycles each second.

  One thousand per second would be a kilohertz and one million a megahertz. One trillion, 10¹², would be a terahertz — one prefix step above giga, a thousand times the figure given.

• practice — not a real PYQ

  In the specification "64-bit processor", the term bit refers to:

  • (a)The number of clock cycles the processor completes each second
  • (b)The width of the data the processor handles in one operation
  • (c)The storage capacity of the hard disk
  • (d)The number of dots the display can show
  Answerb — The bit figure is the width of the registers and data path, that is, how large a chunk of data the processor works on at a time.

  Cycles per second is the clock speed, measured in hertz. Hard disk capacity is measured in bytes. The count of dots on a screen is its resolution in pixels, which belongs to the display rather than the processor.

• practice — not a real PYQ

  The refresh rate of a computer monitor is expressed in:

  • (a)Pixels
  • (b)Bytes
  • (c)Hertz
  • (d)Bits per second
  Answerc — Refresh rate counts how many times the screen is redrawn in one second, which is a frequency, so it is quoted in hertz.

  Pixels count the picture elements that make up the resolution. Bytes measure stored data. Bits per second is a data transfer rate, used for network and interface speeds rather than for redrawing a display.