计算机专业英语教程第5版翻译 绝对准确

Systems, which control scientific experiments, medical computer systems, industrial control systems, and some display systems are real-time systems. 控制科学的实验，医学的计算机系统，工业的控制系统和一些显示系统等系统都是实时系统。

A real-time operating system has well-defined fixed time constraints．实时操作系统有定义明确的固定的时间约束。

Processing must be done within the defined constraints, or the system will fail. 处理必须在定义的约束中完成，否则系统将失败。

A multiprocessor system has more than one CPU. 多处理机系统有不只一个CPU。

The obvious advantages would appear to be greater computing power and reliability. 显著的优势好像是强大的计算能力和可靠性。

There are various types of operating systems for multiprocessors and multicomputers. 有各种各样的操作系统用于多处理机和多计算机。

It is more or less possible to distinguish two kinds of operating systems for multiple CPU systems: Loosely coupled, such as network operating system and distributed o/s, and tightly coupled, such as parallel o/s. 这或多或少可能区分两种多CPU系统的操作系统：松耦合，例如网络操作系统和分布式操作系统，和紧耦合，如并行操作系统。

As we shall see, loosely and tightly-coupled s/w is rought analogous to loosely and tight-coupled h/w. 我们应该看到，松紧耦合软件大概类似于松紧耦合硬件。

The operating system must ensure correct operation of the computer system. 操作系统必须确保改正计算机系统的操作。

To prevent user programs from interfering with the proper operation of the system, the h/w was modified to create two modes: user mode and monitor mode[4]. 为了阻止用户程序干扰系统适当的操作，硬件被修改成两种模式：用户模式和监控模式。

Various instructions(such as I/O instructions and halt instructions) are priviledged and can only be executed in monitor mode. 许多指令（例如I/O指令和中断指令）是有特权的，只能在监控模式下被执行。

The memory in which the monitor resides must also be protected from modification by the user. 监控程序所在的内存也必须保护起来以防用户修改。

A time prevents infinite loops. 定时器可以防止死循环。Once these changes (dual mode, privileged instructions, memory protection, timer interrupt) have been made to the basic computer architecture, it is possible to write a correct operating system. 一旦这些对基本计算机体系结构的改变（双模，权限指令，内存保护，定时器中断）被做到，这可能写成一个改进的操作系统。

《计算机专业英语教程》（第4版）

5.1 Internet

因特网

@ Many networks exist in the world, often with different hardware and software.

许多网络通常会以不同的硬件和软件的形式存在于世上。

People connected to one network often want to communicate with people attached to a different one. attached to 附属于

连接了一个网络的人常常想与附属于一个不相同的网络的人交流。

This desire requires connecting together different, and frequently incompatible networks, sometimes by using