2.1.4 Units, Numbers and Characters

Units
(a) define the terms bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte
Bit =Binary digit 1 or 0
Byte= 8 bits
Nibble= 1/2 byte, 4 bits
Kilobyte= 1024 bytes
Megabyte= 1024 kilobytes
Gigabyte= 1024 megabytes
Terabyte= 1024 gigabytes

(b) understand that data needs to be converted into a binary format to be processed by a computer
Computers only process data in BINARY format.
Binary=base 2
Denary= base 10
Hexadecimal= base 16

Number:
(c) convert positive denary whole numbers (0-255) into 8-bit binary numbers and back
http://www.r9paul.org/wp-content/uploads/2008/05/pic_baseconversion_example.png

(d) add two 8-bit binary integers and explain overflow errors which may occur
When a number is too large to fit the number of bits allocated to it, some bits are 'lost' leaving an incorrect value known as overflow.

(e)convert positive denary whole numbers (0-255) into 2-digit hexadecimal numbers 

(f)convert between binary and hexadecimal equivalents of the same number

(g) explain the use of hexadecimal numbers to represent binary numbers

Hexadecimal numbers are used to represent binary as they are much easier to interpret due to their simple format.

Character:

(h) explain the use of binary codes to represent characters

As computers can only process binary numbers, a method was developed to allow people to use the full set of alphanumeric characters as well as symbols, using binary codes to represent each character and symbol.

(i) explain the term character set

character set-the characters available to a computer

(j) describe with examples (ASCII and Unicode) the relationship between the number of bits per character in the character set and the number of characters which can be represented.

• ASCII- American Standard Code for Information Interchange which has 127 codes. In binary 127 is 01111111 so the system uses 7 bits. This character set is good for text however cannot deal with math symbols and other languages.
• Unicode- There are more than 4 billion characters (including ASCII 127) using 32 bits.