MODD / Mr. Hansen 10/10/2006

Name: _________________________

Test #1a

A calculator is permitted. Do not spend too much time on any single problem. Clues to some problems that you cannot solve initially may be found elsewhere in the test.

Part I: Fill-Ins and Short Essays (6 pts. each).

1.	Note: The first blank should be filled with a word other than “digital” that begins with the letter D. The second blank should be filled with a word that begins with the letter A. The word digital in MODD refers to data that are ____________ , i.e., not continuous. What are examples of continuous (i.e., non-digital) technologies? Something that can fluctuate continuously—voltage, paint, a pencil, photographic dyes, etc.—can represent sound, or images, or whatever we wish. These non-digital technologies are called ____________ .
2.	Morse Code was developed in 1838 by Samuel F. B. Morse, inventor of the telegraph. In Morse Code, each letter of the alphabet is represented by a sequence of short and long sounds, called “dits” and “dahs.” For example, the letter W is “dit dah dah” or “· — —” in printed symbols. SOS becomes “dit dit dit, dah dah dah, dit dit dit.” Is Morse Code a digital technology? Explain your answer briefly.
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3.	Sketch a circuit diagram that captures this logic: ~(A + B) · (B Å C). The symbol Å indicates XOR. If you are stuck, you can purchase a hint for a couple of points.
4.	State Moore’s Law.
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5.	If Moore’s Law continues to hold for the next 30 years, how many more doublings of computer power will occur between now and then? _____ This represents a growth factor of 2 to what power? _____ If today’s PCs run at, say, 2.8 GHz, then approximately how fast will PCs be in the year 2036? _____

6.	The very first IBM PC ran at 4.77 MHz in the fall of 1981 and came with either 16 KB or 64 KB of random access memory (RAM), depending on how the buyer wished to configure the machine. Does the advancement in computing speed and capability over the last 25 years conform approximately to Moore’s Law? (A typical computer of today may run at 2.8 GHz and may have 512 MB of RAM. Such a computer is less expensive, both in absolute dollars and in inflation-adjusted dollars, than the IBM PC of 1981.) Explain your answer, showing your calculations.
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Part II: Multiple Choice and Essay (4 pts. per numbered problem). There are no additional penalty points for wrong guesses.

7.	The prefix “mega” (abbreviated M), when used with Hertz, means . . .
	(A) an unspecified large number (B) quadrillion (C) trillion	(D) billion (E) million
8.	The prefix “mega” (abbreviated M), when used with bytes, means . . .
	(A) 2^10 (B) 2^20 (C) 2^30	(D) 2^32 (E) million
9.	If an audio signal is sampled using 32-bit samples, as is the case with HD (high definition) audio, then each sample can indicate one of how many possible amplitude values?
	(A) 2^16 (B) 16^2 (C) 2^32	(D) 32^2 (E) none of these
10.	Suppose that we wish to sample 4-channel HD audio (32 bits per sample) at 44.1 KHz. The data storage rate (uncompressed) is closest to which of the following?
	(A) 552 kilobits/sec. (69 kilobytes/sec.) (B) 882 kilobits/sec. (110.25 kilobytes/sec.) (C) 5512 kilobits/sec. (689 kilobytes/sec.)	(D) 5.6 megabits/sec. (700 kilobytes/sec.) (E) 8.8 megabits/sec. (1.1 megabytes/sec.)

11.	The qword (64 bits) is an emerging standard for CPUs, operating systems, gaming systems, etc. How many bytes are in a qword?
	(A) 64 (B) 32 (C) 16	(D) 8 (E) 4
12.	Express the hex number B0B0 in decimal (base 10).
	(A) 41,120 (B) 45,232 (C) 51,130	(D) 110,110 (E) 11,001,100
13.	Compute the signal-to-noise ratio for 32-bit samples, considering quantization noise only.
	(A) 192 dBV (B) 96 dBV (C) 48 dBV	(D) 32 dBV (E) 16 dBV
14.	The audio frequencies supported on standard telephone lines (POTS, for “Plain Old Telephone Service”) go all the way up to 3400 Hz. According to _______ , the minimum sampling rate needed in order to represent these frequencies faithfully without aliasing errors is _______ .
	(A) Shannon’s Theorem; 3.4 KHz (B) Shannon’s Theorem; 6.8 KHz (C) Shannon’s Theorem; 6.8 MHz	(D) Nyquist’s Theorem; 6.8 KHz (E) Nyquist’s Theorem; 6.8 MHz
15.	Convert a power ratio of 5,000:1 into decibels.
	(A) 7 dB (B) 17 dB (C) 27 dB	(D) 37 dB (E) 70 dB
16.	An audio engineer says, “Hey, bring that up 5 dB, would you?” What she means is that you should . . .
	(A) double the power (B) triple the power (C) quadruple the power	(D) quintuple the power (E) sextuple the power
17.	When Mr. Hansen reduced the bit depth of the Mustang photo from 24 bits per pixel, to 8 bits per pixel, then to 4 bits per pixel, and finally to 1 bit per pixel, the image . . .
	(A) obtained a larger signal-to-noise ratio (B) became less and less jagged (C) acquired larger and larger pixels	(D) had less and less resolution (E) became more and more “posterized”
18.	The wagon wheel phenomenon (or perhaps we should say, “the car TV ad phenomenon”) occurs when the wheels of moving vehicles appear to be stationary or even rotating the wrong direction. This effect is an example of . . .
	(A) spatial aliasing (i.e., too few pixels of horizontal and vertical resolution) (B) buffer underrun (C) temporal aliasing caused by undersampling (D) temporal aliasing caused by insufficient bit depth (E) temporal aliasing caused by poor palettes

19-20.

Prove that ~(A + ~B) Û (B · ~A) by means of a truth table.

21-22.

Explain why on late-night TV shows, such as Jay Leno’s show or David Letterman’s show, the host usually wears a suit and tie, but never a suit jacket that has a tight striped pattern. Hint: The answer has nothing to do with fashion, but it does have something to do with the fact that a TV screen in the U.S. shows only 720 by 486 pixels. Also, the answer is not that we want to see stripes clearly. After all, in real life, it is fine if a striped suit from a distance simply looks somewhat grayish. Try to use terminology from the course as you write your answer. A short paragraph is expected. You will need to think fairly hard about this question, since although the example of TV hosts’ clothing may have been mentioned in passing, it was certainly not discussed in class.