ch 8 q CIS
How many things can be represented with: a. sevenbits
128
How many things can be represented with: a. four bits
16
How many things can be represented with: a. five bits
32
What is the sampling rate per second that is enough to create reasonable sound reproduction?
40,000
How many bits would be needed to represent a character set containing 45 characters? Why?
6 bits. 63 distinct things can be represented in 6 bits; 31 distinct things can be represented in 5 bits. Therefore 6 bits must be used.
How many things can be represented with: a. sixbits
64
What is the difference between lossless and lossy data compression?
A lossless data compression is one in which no information is lost. A lossy data compression one in which some information may be lost.
Is a stereo speaker an analog or a digital device? Explain.
A stereo speaker is an analog device because it receives an analog representation of the sound wave from the stereo. The speaker receives the signal and causes a membrane to vibrate, which in turn vibrates the air (creating a sound wave), which in turn vibrates your eardrum.
Is a clock with a sweeping second hand an analog or a digital device? Explain.
A sweeping second hand is an analog device. The motion of the hand is continuous.
How is a real value stored in the computer?
Any real value can be described by three properties: the sign (positive or negative one), the digits in the value with the radix point assumed to be to the right, and the exponent, which determines how the radix point is shifted relative to the mantissa. A real number is represented in the computer by storing it as an integer along with information showing where the radix point is.
What do we call the perception of the various frequencies of light that reach the retinas of our eyes?
Color
What does color depth indicate?
Color depth is the amount of data used to represent a color; that is the number of bits used to represent each of the colors in the RGB value.
Why do computers have difficulty with analog information?
Computers are discrete, finite machines. Analog information is continuous and infinite. Thus, computers cannot represent analog information directly; the analog information must be converted into a digital form.
Why is data compression an important topic today?
Data compression refers to reducing the amount of space needed to store a piece of data. Although computer storage is relatively cheep, as the amount of data keeps increasing rapidly the cost of storage is a factor. However, the most important reason for compressing data is that more and more we share data. The Web and its underlying networks have limitations on bandwidth that define the maximum number of bits or bytes that can be transmitted from one place to another in a fixed amount of time.
What does it mean to digitize something?
Digitizing is the act of breaking continuous information into discrete pieces so that we can represent each piece separately.
Convert the rules for subtraction in a sign-magnitude system to the algorithm format.
Find the first number on the number line IF addition Move in the sign direction of second number the specified units ELSE Move in the opposite sign direction of the second number the specified units
The GIF format uses what technique?
GIF uses indexed color.
What is the difference between HiColor and TrueColor?
HiColor uses 16 bits; TrueColor uses 24 bits.
Which produces better sound quality, higher sampling rates or lower sampling rates?
Higher sampling rates produce better sound quality.
How does pixel resolution affect the visual impact of an image?
If enough pixels are used (high resolution) and presented in the proper order side by side, the human eye can be fooled into thinking it's viewing a continuous picture.
What is the technique in which an application supports only a certain number of specific colors, creating a palette from which to choose?
Indexed color
What is the best format for photographic color images?
JPEG
How are the various video codecs alike?
Most video codecs are block oriented; each frame of a video is divided into rectangular blocks.
Do vinyl record albums and compact discs record sound the same way?
No. Vinyl record albums use an analog representation, but compact discs store audio information digitally.
What is pulse code modulation?
Pulse Code Modulation is a signal that jumps sharply between two extremes.
What is an RGB value?
RGB stands for Red, Green, and Blue. The RGB value is actually three numbers that indicate the relative contribution of each of these three colors.
What format stores information on a pixel-by-pixel basis?
Raster-graphics format
What is resolution?
Resolution refers to the number of pixels used to represent a picture.
Describe a situation in which spatial video compression would be effective.
Spatial video compression removes redundant information within a frame. This type of compression is good for landscapes in which there are large blocks of color that are the same such as a blue sky.
Name two types of video compression.
Temporal compression and spatial compression
Explain temporal video compression.
Temporal video compression uses the differences between frames as the basis for compression. A key frame is stored in its entirety and then changes from that key frame are stored.
What is the main difference between the ASCII and Unicode character sets?
The ASCII character set uses 8 bits to represent a character; the Unicode character set does not specify a fixed number of bits, but the most used encoding for Unicode does use 16 bits to represent a character. Thus while ASCII can represent 256 characters this mapping of Unicode can represent over 65000 characters. ASCII is fine for representing English, but the designers
How are they different?
The codecs differ in how the blocks used are encoded.
Is the two's complement of a number always a negative number? Explain.
The two's complement is a way or representing fixed-sized numbers in memory. The two's complement of a number X is just -X in two's complement representation. If X is a positive number, the two's complement of X is negative, but if X is negative, the two's complement is a positive number.
What does an RGB value of (130, 0, 255) mean?
There is a medium contribution of red, no contribution of green, and a full contribution of blue.
Define sampling as it relates to digitizing sound waves.
To digitize the signal, we periodically measure the voltage of the signal and record the appropriate numeric value. Instead of a continuous signal, we have a series of numbers representing distinct voltage values. Thus, we have a sample of the original continuous signal.
What is the format that describes an image in terms of lines and geometric shapes?
Vector graphics
What are the techniques called that shrink the sizes of movies?
Video codecs
How do humans perceive sound?
We perceive sound when a series of air compressions vibrate a membrane in our ear, which sends signals to our brain.
What color does an RGB value of (255, 255, 255) represent?
White
Can fractional values be visually converted between octal and binary and back? Explain.
Whole numbers expressed in binary and octal can be converted visually, moving from the radix point to the left. Fractional values can be read of visually moving from the radix point to the right.
Huffman codes are created based on the _____________ of the character.
analog
______ data is a continuous representation of information.
digital
A computer must use the binary number system to represent information.
f
A computer represents information in an analog form.
f
A keyframe is used in temporal compression to represent the changes from one frame to another.
f
Four bits can be used to represent 32 unique things.
f
In the ASCII character set, there is no distinction made between uppercase and lowercase letters.
f
Indexed color increases the number of colors that can be used in an image, and thus increases the file size.
f
Run-length encoding is very good at compressing English text.
f
An audio signal is digitized by ____ its value at regular intervals.
frequency of use
If the number base is other than base ten, we call the decimal point the ______ point.
radix
An audio signal is digitized by ____ its value at regular intervals.
sampling
The representation for numbers you've used since grade school is called ______.
signed magnitude
A CD stores audio information in a binary format.
t
A digital signal represents one of two values at any point in time.
t
An RGB value represents a color using three numeric values.
t
An audio signal is digitized by sampling it at regular intervals.
t
Bitmap, GIF, and JPEG are all examples of raster-graphics formats.
t
Huffman encoding uses variable-length binary strings to represent characters.
t
Keyword encoding replaces frequently used words with a single character.
t
Lossless compression means the data can be retrieved without losing any of the original information.
t
Overflow occurs when the value that we compute cannot fit into the number of bits we have allocated for the result.
t
The MP3 audio format discards information that can't be heard by humans.
t
The Unicode character set includes all of the characters in the ASCII character set.
t
The signed-magnitude representation of numbers has two representations for zero.
t
Vector graphics represent images in terms of lines and geometric shapes.
t
