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Units, Numbers and
Characters - Computing

1 UNITS

1.1 BIT - smallest unit of data, represented as a
binary number, either 1 (true) or 0 (false)

1.2 BYTE - contains 8 bits, one keyboard
character takes up 1 byte of storage

1.3 NIBBLE - 4 bits, 2 make a byte, less common

1.4 KILOBYTE - unit of storage capacity, 1024 bytes
(or 1000), equivalent to 1024 characters on screen

1.4.1 The more detailed an image, the
more kilobytes of storage it takes up

1.5 MEGABYTE - unit of storage capacity, 1,048,576 bytes
or 1,024 kilobytes (or 1 million bytes/1000 kilobytes)

1.5.1 A typical MP3 song can be anywhere
between 3 to 5 megabytes in size and a CD
can store up to 650 megabytes of data.

1.6 GIGABYTE - 1024 megabytes, a DVD can
store a film around 4-8 gigabytes and hard
disks can hold typically 160+ gigabytes

1.7 TERABYTE - 1024 gigabytes,
can store huge amounts of data

1.8 ANALOGUE DATA - on a continuous
scale, used in the real world

1.8.1 Computers can only deal with digital
data (0 or 1). Analogue data must be
converted to digital using an ADC

2 NUMBERS

2.1 Denary number system:
0, 1, 2, 3, 4, 5, 6, 7, 8, 9

2.1.1 'Base 10' number system

2.1.1.1 Multiply each digit on the left by a progressive factor of 10 in
order to calculate its value e.g. '123' = 3 + (10 * 2) + (100 * 1)

2.2 Binary: 0 or 1

2.2.1 'Base 2' number system

2.2.1.1 Multiply each digit on the left by a
progressive factor of 2 e.g. '37' =
00100101 (1 * 1) + (2 * 0) + (4 * 1)
+ (8 * 0) + (16 * 0) + (32 * 1) = 37