Created 2/13/99; Revised 01/16/00, 06/26/02; 10/04/03

on Analog and Binary Signals

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1. What does the word binary mean?

A.    Binary means "containing a computer."
B.    Binary means "having only two states."
C.    Binary means "having a discrete number of values."
D.    Binary means "using electronics to do arithmetic."

2. What is a bit?

A.    A bit is a single binary value.
B.    A bit is a single character stored in main memory.
C.    A bit is a collection of several bytes.
D.    A bit is a small unit of computer time.

3. Which of the following is NOT an advantage of building computers out of binary devices?

A.    Binary devices are simple and easy to build.
B.    Binary signals are unambiguous.
C.    Binary devices are much faster than decimal devices.
D.    Patterns of bits can be used to represent anything symbolic.

4. What is true of an analog signal?

A.    An analog signal has a discrete number of states.
B.    An analog signal is the only way that music can be recorded.
C.    An analog signal can never be converted into a binary signal.
D.    An analog signal is usually continuously changing in value.

5. If an analog signal picks up some noise, has information been lost?

A.    Yes—the noise hides the exact values of the original signal.
B.    No—electronics can just ignore the noise.
C.    No—information has been added to the signal.
D.    Maybe—it depends on how loud the noise is.

6. If a binary signal picks up some noise, has information been lost?

A.    Yes—the exact value of the bits cannot be determined.
B.    No—the exact value of the bits can be determined, as long as the noise is not too great.
C.    No—binary signals can't pick up any noise.
D.    Yes—the signal will have extra bits in it because of the noise.

7. Why does a computer have a clock?

A.    The state of binary signals is measured only at specific instants in time.
B.    A clock is needed to check how fast signals are changing.
C.    A clock is needed to check that voltage levels are correct.
D.    A clock is used only with application programs that need to know the current time.

8. Can Japanese writing be represented in a computer?

A.    No—only English can be represented.
B.    No—only languages with an alphabet can be represented.
C.    Yes—but a special processor chip is needed.
D.    Yes—since it is symbolic, and anything symbolic can be represented.

9. Can English writing be represented with analog signals?

A.    No—only binary signals can represent symbolic data.
B.    No—it is not symbolic.
C.    No—analog signals don't represent anything.
D.    Yes—just read out loud into a microphone.

10. Why is it important that unlimited perfect copies can be made of data represented in binary?

A.    Because data are copied back and forth between parts of a computer system many times per second.
B.    Transmitting data over the Internet involves making many copies of the data.
C.    Application programs such as wordprocessors and computer games must be perfect copies of the original in order to run.
D.    All of the above.

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