CPSC 100, Fall 1997:
Answers to Quiz #1

This is the first quiz from the course Computer Science 100: Principles of Computer Science, taught by David Eck. The answers that are included here are sample answers only. There might be many other answers to a given problem that would also receive full credit. See the home page for the text, The Most Complex Machine, for more information about the course.


Question 1: Define the term machine language.

Answer: Every type of computer has its own machine language, which consists of instructions that can be executed directly by the CPU of the computer. Instructions in machine language are encoded as binary numbers. Programs written in machine language are executed directly by the computer; programs written in "higher-level languages" must be translated into machine language before they can be executed.

(Note that "machine language" is a very specific technical term that refers exclusively to a programming language. It does not refer to any old language used by a machine. In particular, ASCII code -- which is used to represent textual data -- is not an example of machine language.)


Question 2: What is a byte?

Answer: A byte is an eight-bit binary number. That is, it is a string of eight bits, each of which can be 0 or 1.


Question 3: What is the purpose of a computer's main memory? What is the structure of main memory (that is, how is it organized)?

Answer: The main memory, or RAM, of a computer holds programs and data that are directly accessible to the CPU. The CPU fetches program instructions from memory and carries them out. Main memory is organized as a numbered list of locations. Each location holds a binary number, with some fixed number of bits. In most modern computers, each computer holds one byte, and the size of main memory is usually measured in bytes.


Question 4: Computation can be defined as the mechanical manipulation of symbols. Explain what this means.

Answer: A symbol is something that has no meaning in itself but that can have some kind of externally assigned meaning. For example, a word such as "dog" is a symbol, and a number such as 17 is a symbol. The computer computes by manipulating symbols, but it does so mechanically, that is, by mindlessly following rules that have nothing to do with the meaning of the symbols that are being manipulated. The computer does not "understand" the meaning of what it is doing.


Question 5: What is the Internet?

Answer: The Internet is a computer network that connects millions of computers around the world. Computers on the Internet can share and exchange information. (The World-Wide Web is a huge collection of information organized as "pages" that are stored on computers all over the Internet. The Web is just one of the services offered by the Internet.)


David Eck, 19 September 1997