IPA FE Subject A sample Question 19

A question IPA Japan published in 基本情報技術者試験科目A サンプル問題問19, translated into English. ITPEC is based on the same exams.

Which of the following is a characteristic of DRAM?

a)Writing and erasing are performed all at once or in units of blocks.b)No refresh operation or access operation is required to retain data.c)It can retain stored information even when the power is cut off.d)Since the structure of its memory cells is simple, it can be highly integrated, and its cost per bit can be reduced.

Explanation

A simple cell allows high integration and a low cost per bit — a DRAM cell is one transistor and one capacitor, the charge in the capacitor holding the bit.

With so few parts per bit, many cells fit on a chip, which makes DRAM large and cheap per bit; this is why it is used for main memory. The price is that the charge leaks away, so every cell must be refreshed periodically, and the contents are lost when the power is off.

Answer (d)

Why not others:

•(a) — writing and erasing all at once or block by block is flash memory
•(b) — needing no refresh describes SRAM, whose flip-flop cells hold their state while powered; DRAM must be refreshed
•(c) — keeping data with the power off is non-volatile memory (flash, ROM); DRAM is volatile

Key rule: DRAM: capacitor, refresh needed, dense and cheap per bit, main memory; SRAM: flip-flop, no refresh, fast, cache; flash: non-volatile, erased in blocks.

Computer Component · AI-written, may contain errors

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This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.