Harley Hahn's Guide to
Exercises and Answers for Chapter 3...
The Unix Connection
Review Question #1:
What type of machine was used as the very first Unix terminal? Why was this machine chosen?
The first Unix terminal was the Teletype ASR33. It was chosen because it was inexpensive and available, even though it had been designed for a completely different purpose.
Review Question #2:
What are terminal rooms? Why were they necessary?
Terminal rooms were first used in the 1970s. A terminal room was a room in which there were a number of terminals, each of which was connected to a host computer. When you wanted to use the computer, you would go to the terminal room, and wait for a free terminal.
Terminal rooms were necessary because, at the time, computers (and terminals) were so expensive, they had to be shared.
Review Question #3:
What is a headless system? Give two examples of headless systems that are used on the Internet to provide very important services.
A headless systems is a computer that runs on its own, without direct input from a human being. A typical headless system would be a server, with no monitor, keyboard or mouse. When necessary the server can be controlled via a network connection.
Common examples are Web servers, mail servers, and routers.
Review Question #4:
What is a server? What is a client?
A server is a program that offers a service of some type, usually over a network. (Sometimes, the term "server" refers to the computer that runs the server program.)
A client is a program that requests a service from a server.
For example, when you use the Web, your browser is the client and the Web server is the server.
For Further Thought #1:
In 1969, Ken Thompson of AT&T Bell Labs was looking for a computer to create what, eventually, became the first Unix system. He found an unused PDP-7 minicomputer, which he was able to use. Suppose Thompson had not found the PDP-7. Would we have Unix today?
No, we wouldn't.
The genesis of every great invention involves some degree of serendipity. Because no one (least of all Thompson) know how important Unix was to become he initially received no direct support from Bell Labs. If he had not found the hardware he needed, he probably would have moved on to another project, one that was funded.
On the other hand, the ideas expressed in the early versions of Unix were a product of the times. No doubt that, one way or another, the basic insights underlying Unix would have been expressed eventually.
Thus, although we wouldn't have had Unix, we would have had something comparable, maybe even better.
For Further Thought #2:
In the 1970s, computers (even minicomputers) were very expensive. Since no one had their own computer, people had to share.
Compared to today, computers in the 1970s were slow, with limited memory and storage facilities. Today, every programmer has his own computer with very fast processors, lots of memory, lots of disk space, sophisticated tools, and high-speed Internet access.
Who had more fun, programmers in the 1970s or programmers today?
How about programmers 20 years from now?
Programming today is a much faster, less frustrating activity than it was in the 1970s. Moreover, because of the Internet, the world of programming is richer and more complex. Learning and finding help are a lot easier than they used to be.
However, programmers in the 1970s had a more fun, because they worked in a environment in which they interacted with their colleagues in person. Indeed, for many years, Unix was mostly an oral tradition, with the written material acting only as a reference.
Although programmers today all have access to fast, inexpensive, powerful computers of their own, as well as sophisticated tools that weren't even dreamed of in the 1970s, none of that can replace the need for human beings to work together, face-to-face, at least some of the time. Moreover, when computers were expensive, they needed to be shared, creating an work environment in which programmers felt connected to something important that was bigger than themselves.
Long before 20 years have passed, it will be recognized that, in order the thrive, people require communication with other people in person. Once this biological need is met, the programmers of the future will be more happy than the programmers of the 1970s.
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