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Computer AwarenessMedium

Which type of memory has to be refreshed thousands of times per second to retain its contents?

  1. A.SRAM
  2. B.DRAM
  3. C.ROM
  4. D.Flash memory

Correct answer

B. DRAM

Explanation

The correct answer is B, DRAM. Dynamic RAM stores each bit as a charge on a very small capacitor, and that charge leaks away in a few milliseconds, so the memory controller has to read and rewrite every cell continuously. The word dynamic in the name refers to exactly this refresh cycle.

Option A, SRAM, stores a bit in a flip-flop of transistors that holds its state as long as power is supplied, so it needs no refreshing at all; that is what makes it fast enough for cache and too costly for main memory. Option C, ROM, is non-volatile and keeps its contents even without power, so refreshing does not apply. Option D, flash memory, is also non-volatile: it traps charge in a floating gate that holds for years, which is why pen drives and SSDs survive being unplugged. Only dynamic RAM is refreshed.

Read the full article: Memory and Storage: RAM, ROM, Cache and Units

Practice Questions

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Q2.Computer AwarenessEasy

How many bits make one nibble?

  1. A.2 bits
  2. B.4 bits
  3. C.8 bits
  4. D.16 bits
Show answer
Correct answer: B. 4 bits

A nibble is half a byte, that is four binary digits, and it matters because one nibble is written as exactly one hexadecimal digit, from 0 to F. That is why memory addresses in hexadecimal are read four bits at a time.

Q3.Computer AwarenessMedium

The contents of an EPROM chip are erased by exposing it to

  1. A.An electrical signal
  2. B.Ultraviolet light
  3. C.A magnetic field
  4. D.Infrared radiation
Show answer
Correct answer: B. Ultraviolet light

An Erasable Programmable Read Only Memory chip carries a small quartz window over the silicon; ultraviolet light shone through that window releases the trapped charge from every cell at once and returns the chip to its blank state, after which it can be programmed again.