Unit 2 - Chapter 4

Question 1

External Representation

Answer 1

the way information is represented by humans and the way it is entered at a keyboard or displayed on a printer or screen.

Question 2

Internal Representation

Answer 2

the way information is stored in the memory of a computer

Question 3

Binary Numbering System

Answer 3

Binary is a base-2 positional numbering system. There are only two digits, 0 and 1, and the value of the positions in a binary number is based on powers of 2.

Question 4

Maximum number of binary digits that can be used

Answer 4

Typically this value is 16,32, or 64 bits.

Question 5

Arithmetic overflow

Answer 5

An attempt to represent an integer that exceeds the maximum allowable value.

Question 6

Computer Science

Answer 6

Must del with a finite and sometimes quite limited set of possible representations and it must handle the errors that occur when those limits are exceeded.

Question 7

Signed numbers

Answer 7

To represent signed integers ( in binary) we can use the left most bit of a number to represent a sign, with 0 meaning positive ( +) and 1 meaning negative ( - ). This form of signed integer representation is termed => signed/ magnitude notation, and it is one of a number of different techniques for representing positive and negative whole numbers. Disadvantage => This technique causes the issue of + 0 / - 0

Question 8

The meaning of a binary number stored in memory

Answer 8

is based solely on the context in which it is used. The context determines the meaning of a binary string.

Question 9

Two’s complement representation

Answer 9

The positive numbers begin at 000…and proceed in order around the circle to the right, Negative numbers begin at 111 and proceed in order around the circle to the left. The leftmost digit specifies whether the number is to be given a positive interpretation ( leftmost bit = 0 ) or a negative interpretation ( left most bit = 1 ) ====»> there is only one single zero, the binary number 000… DISADVANTAGE: you can always represent one more negative number than positive

Question 10

Fractional Numbers

Answer 10

To represent fractions in binary you must first convert the number to scientific notation. +-M x B +-E
M = Mantissa
B= exponent base
E = exponent
** The mantissa ( or significand or coefficient) is part of a number consisting of its significant digits
For example:
0.6259 x 10 to the power of 3
0.6259 is significant
10 is the base
3 is the exponent
In a floating point number the first bit is the sign ( + or - ) the net bits are for the exponent and the rest is for the significand.

Question 11

Textual Information

Answer 11

To represent textual material in binary, the system assigns each printable letter or symbol in our alphabet a unique number, and then stores that symbol internally using the binary equivalent of that number.

Question 12

ASCII

Answer 12

Currently, the most widely used code for representing characters internally in a computer system is called ASCII, an acronym for the American Standard Code for information exchange. ASCII is an international standard for representing textual information in the majority of computers. It uses 8 bits to represent each character, so it is able to encode a total of 2 to the power of 8 or 256 different characters . These are assigned the integer values 0 to 255.

Question 13

Unicode

Answer 13

a code set that has gained popularity because it uses 16-bit representation for characters. This means it is able to represent 2 to the power of 16 = 65,536 unique characters. This is especially important for representing emojis and characters other than English.

Question 14

Analog Representation

Answer 14

objects can take on any value. Amplitude => loudness => the greater the amplitude the louder the sound. => the Period of the wave designated as T is the time is takes for the wave to make one complete cycle. => The frequency is the total number of cycles per unit measured in cycles/second, also called hertz and defined as f= 1/T
***** The frequency is a measure of pitch, the highness or loudness of a sound. The higher the frequency, the higher the perceived tone.
===»> Human ear can generally detect sounds in the range of 20 to 20,000 hertz.

Question 15

To store a waveform in a computer

Answer 15

the analog signal must first be digitized, that is, converted to a digital representation.

Question 16

sampling

Answer 16

At fixed time intervals, the amplitude of the signal is measured and stored as an integer value. The wave is thus represented in digital form as a sequence of sampled numerical amplitude.

Question 17

Accuracy of Sound

Answer 17

The accuracy with which the original sound can be reproduced is dependent on two key elements - the sampling rate and the bit depth.

Question 18

Sampling rate

Answer 18

measures how many times per second we sample the amplitude of the soundwave. The more often we sample, the more accurate the reproduction. Also, the more often we sample, the greater the range of frequencies that can be captured.

Question 19

Bit depth

Answer 19

The number of bits used to encode each sample.
==»> Most audio encoding schemes today use either 16 or 24 bits per sample level, allowing for either 65K or 16M distinct amplitude levels.

Question 20

Scanning

Answer 20

Measuring the intensity values of distinct points located at regular intervals across the image surface. These points called pixels are picture elements. The more pixels used, the more accurate the encoding of the image.

Question 21

Raster graphics

Answer 21

Used by well-known graphics standards such as JPEG ( join photographer experts group), GIF ( graphics Interchange Format), and BMP ( bitmap). It is a dot matrix data structure that represents a generally rectangular grid of pixels, viewable via a computer display, paper, or other display medium.

Question 22

To digitize images, black and white or colour,

Answer 22

we measure the intensity value of the image at a discrete set of points. For colour, we need to store more information about each pixel.

Question 23

RGB encoding scheme

Answer 23

Most common format for storing colour images, RGB is an acronym for red green blue. This technique describes a specific colour by capturing the individual contribution to a pixel’s colour of each of the three colours. It uses one byte for each colour, allowing us to represent an intensity range from 0 to 255.

Question 24

True colour

Answer 24

24 bit colour encoding scheme or 2 power 24 distinct colours approximately 16.7 million. The encoding scheme use in the JPEG format.

Question 25

Color palette

Answer 25

Technique used in the Graphics Interchange Format ( GIF), which uses a palette that can hold as few as 2 colours or as many as 256.
===» This is also called colour lookup palette ( CLUT). A palette is a correspondence table in which selected colours from a certain color space’s color reproduction range are assigned an index, by which they can be referenced.
===» By referencing the colors via an index, which takes less information than the one needed to describe the actual colors in said color space, this technique aims to reduce data usage, be it as processing payload, transfer bandwith, RAM usage or persistent storage.
===» Images in which colors are indicated by references to a CLUT are called indexed colour images.

Question 26

Data Compression

Answer 26

Data compression algorithms attempt to represent information in ways that preserve accuracy while using significantly less space

Question 27

Run-length encoding

Answer 27

This method replaces a sequence of identical values ( V1, V2, V3) by a pair of values ( V, N) which indicates the value v is replicated n times.

Question 28

Compression ration

Answer 28

measures how much they reduce the storage requirements of the data : compression ratio = size of the uncompressed data / size of the compressed data

Question 29

Lossless compression

Answer 29

This means that no information is lost in the compression, and it is possible to exactly reproduce the original data

Question 30

Lossy compression schemes

Answer 30

compress data in a way that does not guarantee that all of the information in the original data can be fully and completely recreated.

Question 31

transitor

Answer 31

a solid-state device that has no mechanical or moving parts ( electronic device). It is bistable. It can be in an off state, which does not allow electricity to flow, or in an ON state, in which electricity can pass unimpended. The switching of a transistor from the OFF to the On state, and vice-versa, is done electronically rather than mechanically. This allows the transistor to be fast as well as extremely small.

Question 32

Boolean Logic

Answer 32

Area of mathematics that deals with rules for manipulating the two logical value true and false. Used to construct circuits that perform operations such as adding numbers, comparing numbers and fetching instructions. In Boolean logic, the operations used to construct Boolean expressions are AND, OR< & NOT and they map a set of ( true, false) values into a single ( true, false) result.

Question 33

AND & OR

Answer 33

require two operands and are therefore called binary equators

Question 34

NOT

Answer 34

requires only one operand and is called a unary operator like the square root operator in arithmetic

Question 35

Tautology

Answer 35

A Boolean expression that is always true.

Question 36

Gates

Answer 36

A gate is an electronic device that operates on a collection of binary inputs to produce a binary output. That is, it transforms a set of ( 0,1) input values into a single ( 0,1) output value according to a specific transformation rule.

Question 37

Computer Circuit

Answer 37

A circuit is a collection of logic gates that transforms a set of binary inputs into a set of binary outputs and in which the values of the outputs depend only on the current values of the inputs.

Question 38

Compare-for-equality circuit or CE circuit

Answer 38

Tests two unsigned binary numbers for exact equality. The circuit produces the value 1 ( true) if the two numbers are equal and the value 0 ( false) if they are not.

Question 39

Full added

Answer 39

An addition circuit that performs binary addition on tow unsigned N-bit integers.

Question 40

Control Circuits

Answer 40

are used not to implement arithmetic operations but to determine the order in which operations are carried out and to select the correct data values to be processed. Sequencing and decision making inside a computer.