問80
頻出度★☆☆
プリンタへの出力処理において, ハードディスクに全ての出力データを一時的に書き込み, プリンタの処理速度に合わせて少しずつ出力処理をさせることで, CPUをシステム全体で効率的に利用する機能はどれか。
平成27年度 春期 ITパスポート試験 問80
テクノロジ系ソフトウェア › オペレーティングシステム
This question's explanation and your answers so far.
解説
問 80
Incorrectア
An add-on is an extension program that later adds functions to existing software (a browser extension, for example). It is a mechanism for adding functionality, not for temporarily holding print data to absorb a speed difference.
- イ
正解 The correct answer is イ, Spool. A printer is far slower than the CPU, so if the CPU keeps waiting until printing is finished, it cannot do anything else in the meantime and overall efficiency drops. The OS therefore first writes the output data into a queue (a spool file) on fast auxiliary storage (the hard disk); the CPU is released from the print processing there and moves on to its next job. After that, data is sent out from the spool little by little, matching the printer's processing speed. This mechanism — absorbing the speed difference with a slow output device by using auxiliary storage so that the CPU is used efficiently across the whole system — is spooling, and it matches the stem exactly.
Incorrectウ
Defrag (defragmentation) is maintenance work that rearranges files scattered in fragments on the hard disk into continuous areas so that reading and writing become faster. It may look similar because it also deals with the hard disk, but its purpose is to improve disk access, not to store printer output temporarily.
Incorrectエ
Plug and Play is a function by which, when a peripheral device is connected, the OS automatically recognizes the device and configures its driver so that it can be used right away. It is a mechanism that makes installing and setting up devices easier, and it has nothing to do with CPU efficiency during output processing.
ここがポイント
- Spooling: an OS function that first writes data destined for a slow output device (such as a printer) to auxiliary storage, releases the CPU instead of making it wait, and then sends the data out in order at the device's speed. Its purpose is to absorb the speed difference and raise CPU utilization.
- Distinguish easily confused OS / peripheral-device terms: add-on = adding functionality, defrag = eliminating disk fragmentation, Plug and Play = automatic recognition and configuration of a connected device.
用語