1. Data representation

Question 1

What must any form of data be converted into for a computer to process it?

Answer 1

Binary format

Question 2

What does the binary number system consist of?

Answer 2

1s and 0s

Question 3

Why is the binary number system chosn?

Answer 3

Since computers contain millions and millions of tiny ‘switches’, which must be in the ON or OFF position, they can be represented by 1s and 0s.

Question 4

How and why are switches used?

Answer 4

Switches used in a computer make use of logic gates and are used to store and process data.

Question 5

How is binary converted to denary?

Answer 5

Each time a 1-value appers in a binary number column, the column value is added to a total.

Question 6

How is denary converted to binary?

Answer 6

Subtract the largest power of 2 and keep doing this until the value of 0 is reached.
OR
Successively divide by 2 by writing the result of the division including the remainder (even if it is 0) under the dividend until the result is zero. Write down all the remainders in reverse order.

Question 7

What is the hexadecimal number system?

Answer 7

Hexadecimal is a base 16 system and therefore needs to use 16 different ‘digits’ to represent each value. The numbers 0 to 9 and the letters A to F are used to represent each hexadecimal digit. A in hex = 10 in denary, B = 11, C = 12, D = 13, E = 14, F = 15.

Question 8

How is binary converted to hexadecimal?

Answer 8

Starting from the right and moving left, split the binary number into groups of 4 bits. If the last group has less than 4 bits, then simply fill in with 0s from the left. Take each group of 4 bits and convert it into the equivalent hexadecimal digit.

Question 9

How is hexadecimal converted to denary?

Answer 9

Take each of the hexadecimal digits and multiply it by the heading values. Add all the resultant totals together to give the denary number.

Question 10

How is denary converted to hexadecimal?

Answer 10

Successively divide by 16 by writing the result of the division including the remainder (even if it is 0) under the dividend until the result is zero. Write down all the remainders in reverse order.

Question 11

Why is hexadecimal more convenient to use than binary?

Answer 11

One hex digit represents four binary digits. The hex number is far easier for humans to remember, copy, and work with.

Question 12

What are four uses of the hexadecimal system?

Answer 12

Error codes, MAC addresses, IPv6 addresses, HTML colour codes

Question 13

What are error codes?

Answer 13

Error codes refer to the memory location of the error and are usually automatically generated by the computer. The programmer needs to know how to interpret the hexadecimal error codes.

Question 14

What are Media Access Control (MAC) addresses?

Answer 14

Media Access Control (MAC) address refers to a number which uniquely identifies a device on a network. The MAC address refers to the network interface card (NIC) which is a part of the device. The MAC address is rarely changed so that a particular device can always be identified no matter where it is. A MAC address is usually made up of 48 bits which are shown as 6 groups of two hexadecimal digits where the first half is the identity number of the manufacturer of the device and the second half is the serial number of the device.

Question 15

What are Internet Protocal (IP) addresses?

Answer 15

Each device connected to a network is given an address known as the iNternet Protocal (IP) address. An IPv4 address is a 32-bit number written in denary or hexadecimal form. IPv4 has recently been improved upon by the adoption of IPv6. An IPv6 address is a 128-bit number broken down into 16-bit chunks, represented by a hexadecimal number. IPv6 uses a colon (:) rather than a decimal point (.) as used in IPv4.

Question 16

What are HyperText Mark-up Language (HTML) colour codes?

Answer 16

HyperText Mark-up Language (HTML) is used when writing and developing web pages. HTML isn’t a programming language but is simply a mark-up language. A mark-up language is used in the processing, definition, and presentation of text. HTML uses <tags> which are used to bracket a piece of text. HTML is often used to represent colours of text on the computer screen. All colours can be made up of different combinations of the three primary colours (red, green, and blue). The different intensity of each colour (red, green, and blue) is determined by its hexadecimal value. This means different hexadecimal values represent different colours. The # symbol always precedes hexadecimal values in HTML code. The colour codes are always six hexadecimal digits representing the red, green, and blue components. There are a possible 256 values for red, 256 values for green, and 256 values for blue giving a total of 16,777,216 possible colours.</tags>

Question 17

What is an overflow?

Answer 17

A generation of an additional bit from binary addition indicates that the sum has exceeded its maximum value, causing an overflow error where a number is too big to be stored in the computer using its set amount of bits.

Question 18

What is a logical shift?

Answer 18

Computer can carry out a logical shift on a sequence of binary numbers. The logical shift means moving the binary number to the left or tot he right. Each shift left is equivalent to multiplying the binary number by 2 and each shift right is equivalent to dividing the binary number by 2. As bits are shifted, any empty positions are replaced with a zero.

Question 19

What is two’s complement?

Answer 19

To allow the possibility of representing negative integers we make use of two’s complement. In two’s complement the leftmost bit is changed to a negative value. For an 8-bit number, the value 128 is now changed to -128, but all the other headings remain the same. This means the new range of possible numbers is: -128 (10000000) to +127 (01111111).

Question 20

What is ASCII code?

Answer 20

The ASCII code system (American Standard Code for Information Interchange) was set up in 1963 for use in communication systems and computer systems. A newer version of the code was published in 1986. The standard ASCII code character set consists of 7-bit codes that represent the letters, numbers, and characters found on a standard keyboard, together with 32 control codes.

Question 21

What is extended ASCII?

Answer 21

Extended ASCII uses 8-bit codes, giving another 128 codes to allow for characters in non-English alphabets and for some graphical characters to be included.

Question 22

What is the biggest disadvantage of ASCII code?

Answer 22

The main disadvantage is that it does not represent characters in non-Western languages, for example Chinese characters.

Question 23

What is Unicode?

Answer 23

Unicode can represent all languages of the world, thus supporting many operating systems, search engines, and internet browsers used globally. There is an overlap with standard ASCII code, since the first 128 (English) characters are the same, but Unicode can support several thousand different characters in total. ASCII uses one byte to represent a character, whereas Unicode will support up to four bytes per character. The goals of the Unicode is to create a universal standard that covered all languages and all writing systems, produce a more efficient coding system than ASCII, adopt uniform encoding where each character is encoded as 16-bit or 32-bit code, create unambiguous encoding where each 16-bit and 32-bit value always represents the same character, and reserve part of the code for private use to enable a user to assign codes for their own characters and symbols.