计算机外文翻译27

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1、- 1 - 外文原文 Chapter 16: Libraries, Objects, and Library Lists Overview The AS/400 has a complex architecture. In order to effectively operate, administer, and program this machine, you need to understand the main concepts about this architecture. This chapter explains them. Before you start, you shou

2、ld know that the AS/400 architecture is derived from the System/38s architecture. If you are familiar with the S/38, you already know a great deal about the AS/400. You probably even know enough to be able to skip most of this chapter. Single-Level Storage. The AS/400 is a single-level storage machi

3、ne. To the operating system, both memory and DASD (Direct Access Storage Device, or “disk“) are treated the same. When a program runs and it needs to retrieve a piece of information, all the program needs to know is a single address. The operating system uses this address to retrieve the information

4、 whether it is in memory or DASD. In addition, the AS/400 doesnt need to store an object in a single, continuous space on DASD. If you have a large file, for example, the file may be split in dozens or hundreds of small pieces and spread across several physical DASD units. The advantage is immediate: neither the operating system nor the person who uses the system needs to worry about reserving enough space for objects because the system automatically uses whatever space is available, even if t