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AP Computer Science Principals Final
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AP Computer Science Principals Final
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AP Computer Science Principals Final8 bits is enough to represent 256 different numbers. How many
total bits do you need to represent 512 (twice as many) numbers
Correct Answers 9 bits
A bakery collects data on sales. Each sales record includes the
date of the sale and some metadata about the items that were
part of the sale. The data includes: the names of the items sold,
the types of the items sold, the number of each item sold, and
the prices of each item sold. Which of the following CANNOT
be determined from the bakery's data set? Correct Answers
Which customer buys the most bread.
A binary message consisting of four bits was sent to you by a
friend. The message was supposed to be ABAB. Unfortunately,
your friend set the bit on the wire once every 2 seconds, but you
read the wire once every second. Assuming that the first bit was
sent and read at the same time, what message did you receive
instead? Correct Answers AABB
A compression scheme for long strings of bits called run-length
encoding is described as follows: Rather than the record each 0
and 1 individually, instead record "runs" of bits by storing the
number of consecutive 1s and 0s that appear. Since it's binary,
any run of 0s must be followed by a run of 1s (even if the run is
only 1-bit long) and vice versa. Thus, you can store a list of
small numbers that represents the alternating runs of 0s and 1s.
Example below. To uncompress the data back into its original
binary state, you simply reverse the process. This technique is an
, example of what type of compression? Correct Answers
Lossless Compression
A middle school is expanding to open a high school next year,
doubling the total number of students. The school keeps a
database in which each student's unique ID number is stored as
an 8 bit number called studentID. Before the arrival of the new
students almost every 8 bit number has already been assigned to
a student. Which is the most accurate description of how the
school could modify the way studentID is represented in the
database to ensure each incoming student receives a unique ID?
Correct Answers Adding one extra bit to the student IDs will
allow the school to double the amount of unique ID codes.
A raw digital sound file samples a sound wave at some interval
and measures the height of the wave at each point. Thus, raw
sound is recorded as a list of numbers. In very broad terms the
MPS audio compression algorithm identifies frequencies and
volume levels, - low and high - that are outside the range of
human hearing and removes the data representing these
frequencies from original. This technique results in a smaller
audio file that sounds exactly the same to the human ear.
Correct Answers Lossy Compression
A school starts tracking which websites each computer in the
school is visiting by monitoring the packets leaving the school.
A sample of the information they have collected will be given.
Correct Answers Which websites are most frequently visited
before and after school hours from a school computer
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