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Data Representation (Computing Units and Binary (Computing Units (Byte…
Data Representation
Computing Units and Binary
Why Binary?
Humans evolved a number system based on 10 fingers. We call this base 10 or
DENARY
.
Because therre is only 2 possibilities we say that this is a base 2 numebr system or a
BINARY
system.
DENARY must be converted into BINARY and back again when computers do calculations for us.
Computers can only understand
1
s and
0
s because they use tiny electronic switches (transistors) that can be either
on
or
off
.
To digitise something literally means to convert it into a binary form.
Computing Units
Kilobyte (kB)
However, because computers count in binary, 1 kB is actually 1024 bytes (you can use either in the exam!)
1kB of memory could store rougly one full A4 page of text
Can be thought of as 1000 bytes
Megabyte (MB)
However because computers count in binary 1 MB is actually 1024 kB (you can use either in the exam!)
We commonly use megabytes to measure transmission speeds on the web and also storage space on a CD. Be careful! there is a big difference between, say, 20 megabytes per second and 20 megabits per second!
Can be thought of as 1000 kilobytes
Byte
Values 00000000 (0) up to 11111111 (255)
e.g. 29 = 00011101 78 = 01001110 11 = 00001011
8 bits
Every other storage unit is made up of multiples of bytes
Gigabyte (GB)
1GB could roughly hold 25% of a movie or 3000 books
We commonly use GB when describing how big a hard drive or DVD is
Can be thought of as 1000 megabytes
Nibble
Values 0000 (0) up to 1111 (15)
A nibble is really useful when converting between binary and hexadecimal
4 bits
Also used for binary coded decimal (BCD) where 1 nibble is used to store each digit e.g. 29 = 0010 1001 e.g. 11 = 0001 0001
Terabyte (TB)
Can be thought of as 1000 gigabytes
1TB could roughly hold 300 hours of video
Bit
1 (true) or 0 (false)
Smallest unit of data a computer can store
A 'bit' is a Binary Digit
Petabyte (PB)
1PB is a massive amount of storage
1PB could roughly hold 2000 years worth of songs played back to back
Can be thought of as 100 terabytes
1PB could roughly hold 315 million photos