AP Computer Science Principles Unit 1

What is the best explanation for why digital data is represented in computers in binary?

• The binary number system is the only system flexible enough to allow for representing data other than numbers.

• It's easier, cheaper, and more reliable to build machines and devices that only have to distinguish between binary states.

• It typically takes fewer digits to represent a number in binary when compared to other number systems (for example, the decimal number system)

• It's impossible to build a computing machine that uses anything but binary to represent numbers

What is the 4-bit binary number for the decimal number Ten (10)?

• 0010

• 1010

• 0110

• 0101

Number systems with different bases such as binary (base-2) and decimal (base-10) are all used to view and represent digital data.

Which of the following is NOT true about representing digital data?

• At one of the lowest levels of abstraction, all digital data can be represented in binary using only combinations of the digits zero and one.

• The same value (number) can have a different representation depending on the number system used to represent it.

• Groups of bits can be used to represent abstractions, including but not limited to numbers and characters.

• Some large numbers cannot be represented in binary and can only be represented in decimal.

Consider the following three binary numbers:

01010 010000 1110

Which of the following lists the numbers in order from least to greatest?

• 010000, 1110, 01010

• 01010, 1110, 010000

• 01010, 010000, 1110

• 1110, 01010, 010000

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. Of the options provided below, which is the smallest change to the way studentID is represented necessary to ensure each incoming student receives a unique ID?

• Add a bit to studentID to double the number of IDs that the database can represent.

• Double the number of bits in studentID to double the number of IDs that the database can represent

• Keep using an 8-bit number for studentID but reserve the first bit to indicate middle school or high school.

• Remove a bit from studentID to make room for incoming students

8 bits is enough to represent 256 different numbers. How many total bits do you need to represent 512 (twice as many) numbers?

• 9 Bits

• 10 Bits

• 16 Bits

• 17 Bits

ASCII is a character-encoding scheme that uses a numeric value to represent each character. For example, the uppercase letter "G" is represented by the decimal (base 10) value 71. A partial list of characters and their corresponding ASCII values are shown in the table below.

ASCII characters can also be represented by binary numbers. According to ASCII character encoding, which of the following letters is represented by the 8-bit binary value: 0100 0010

• ASCII Character: A

• ASCII Character: B

• ASCII Character: D

• The table does not contain the value represented by the binary number 0100 0010

Two students have developed a protocol in which they send 4-bit messages to each other. They decide to modify their protocol to start sending 8-bit messages instead. How many more values can be represented in an 8-bit message than a 4-bit message?

• 2¹ = 2 times as many values

• 2²= 4 times as many values

• 2³ = 8 times as many values

• 2⁴ = 16 times as many values

The colors of the pixels in a digital image are often represented by red, green, and blue values between 0 and 255 (an RGB triplet). A photographer is manipulating a digital image to lighten it because all of the RGB values in the image are less than 100, making it very dark. He does this by adding 20 to the R, G, and B values of each pixel, then overwriting the original image. What type of transformation is the photographer using on the digital image?

• Lossless transformation

• Lossy transformation

• Multiband transformation

• Chrome Sampling transformation

Select the answer that lists the units of bytes in ascending order (from smallest to largest)

• gigabyte, megabyte, terabyte

• megabyte, terabyte, kilobyte

• gigabyte, terabyte, megabyte

• kilobyte, gigabyte, terabyte