[Decimus]

Originally Posted by takahara24

my homework

write an informative essay on one of the computer system types choose.(Physical,Abstract,Open,Closed)

This is not an English question. This is an IT/CS question instead.

Now, judging from what I'd remembered from my CS (Computer Science) classes...

A Computer is a device（道具） that computes, or in other words, it's a machine that receives input, stores and manipulates inputted data, provides output in a useful manner, and is programmable. (データを「入力」、「記憶」、「制御」、「演算」、� �出力」する機能がある機械です。　プログラミング可� �も必要です。)

A Physical Computer (物性コンピュータ) is a hardware-based device that computes. It has physical components. Your PC, or a Mac, or your cellphone/mobile phone/keitai, are physical computers.

An Abstract Computer (抽象コンピュータ) is a theoretical model　(理論的なモデル) of computer hardware or a software system. A Turing Machine is one example. An abstract computer does not have actual physical parts (物性・現実的な構成部分がない), 'though it may be modelled with an actual object instead of being purely imaginary. For example, if somebody writes a paper （論文） explaining how the CPU (中央処理装置) of your computer works, then what is written on the paper itself (or at least on the parts of the paper that describes the operation of your computer in detail) can be considered to be an abstract computer.

Note that the actual physical paper itself is not an abstract computer -- it's what is written on the paper instead.

Abstract computers can also be modelled on other, actual physical computers. Emulators are one example; these software run simulations (模擬システム) of other actual physical computers, allowing another physical computer to emulate the functions of a different physical computer. （ほかの物性コンピュータを模倣できさせる。）The simulated physical computer is a simulation, not an actual physical computer, and therefore it is abstract, not real, and hence is an abstract computer. （その模擬られたコンピュータは模擬システムだから、 仮想的な物なので、現実のコンピュータではなくて、抽 象的なコンピュータです。）

A better example would be Virtual Machines(仮想機械).

Open Computers, or Open Systems, are computer systems where system access is not controlled by people responsible for the content of electronic records in the system. This forum, JapanForum, is one example; we, the users, are responsible for the content of the posts, but system access is controlled by the admins and moderators.

(Note that JapanForum is hosted on an actual computer server. The computer server itself is an example of a Physical Computer.)

Closed Computers, or Closed Systems, in contrast, are computer systems where system access is controlled by people who are responsible for the content of electronic records in the system. As an example, if you use Microsoft Word on your computer to type a document, then you control access to your computer and are responsible for the content that you create (the documents), so this is considered to be a closed system.