Chapter 0: Introduction

I have read the introduction before, when I first bought this book.

And the day I bought the book, it was two years ago. I am like this, I bought a lot of books about technology, these books are very expensive and expensive, but after the purchase came back to read the first chapter, and then has been thrown aside, let the dust accumulation, nor distressed. I don't know why I'm like this.

Well, don't say it, it's far away.

Said is an introduction, it must be with you what is the operating system, the main thing is to talk about the history of the operating system, said some knowledge about the hardware, said some basic operating system concepts, such as process, address space, as well as files and so on. Although not deep, but with my current skill to see, still feel a little difficult. So the difficulty of the later chapters can be imagined.

Keep in mind that the two most important features of the operating system are the abstraction and management of computer resources for user programs.

The concrete is really not to say, typing is very tired. I just write the problem.

1, what is multi-channel program design?

This question draws a picture to understand. But here I can't draw ...

So I can only write. On IBM 7094, if the current job is paused due to a tape or other I/O operation, the CPU can simply tread until the I/O is complete. For CPU-intensive scientific computing problems, I/O operations are few and therefore waste less time. However, for commercial data processing, I/O operations typically take up to 80% to 90% of the time, so some measures must be taken to reduce the wasted CPU idle time.

The solution is to divide the memory into several parts, each of which has different jobs. When a job and so on I/O operations are complete, the other job can use the CPU. If you can store enough jobs in memory at the same time, the CPU utilization can be close to 100%. Hosting multiple jobs in memory at the same time requires special hardware to protect them from the theft or attack of information on the job.

(There are still a lot of exercises to be continued ....) ）

Chapter 0: Introduction