Binary and data · KS3 Computing

Binary

Computers use binary (base 2) because their circuits are either off (0) or on (1).
A bit is a single 0 or 1. A nibble is 4 bits. A byte is 8 bits.
In an 8-bit number, the place values are 128, 64, 32, 16, 8, 4, 2 and 1. So 00001101 = 8 + 4 + 1 = 13, and the largest 8-bit number, 11111111, is 255. 8 bits can store 256 different values (0 to 255).
To convert denary to binary, take away the biggest place values that fit: 45 = 32 + 8 + 4 + 1 = 00101101.

Binary addition rules: 0 + 0 = 0, 0 + 1 = 1, 1 + 1 = 10 (write 0, carry 1), and 1 + 1 + 1 = 11 (write 1, carry 1).
Overflow happens when the answer needs more bits than are available.
Hexadecimal (base 16) uses the digits 0 to 9 and the letters A to F (10 to 15). One hex digit stands for 4 bits, so hex is a short way of writing binary: FF = 255.

1 kilobyte (KB) = 1000 bytes; 1 megabyte (MB) = 1000 KB; 1 gigabyte (GB) = 1000 MB; 1 terabyte (TB) = 1000 GB. (You may also see 1024 used.)

A character set gives each character a binary code. ASCII uses 7 bits for 128 characters (A is 65). Unicode has far more, including other alphabets and emoji.
An image is made of pixels. Colour depth is the number of bits per pixel: 1 bit gives 2 colours, and 8 bits give 256 colours. Resolution is the number of pixels.
More pixels or a greater colour depth gives better quality but a bigger file.
Sound is stored by taking samples of the sound wave many times a second.

Binary: The base-2 number system, using only 0 and 1.
Bit: A single binary digit, 0 or 1.
Byte: A group of 8 bits.
Denary: The base-10 number system we normally use.
Overflow: When a result needs more bits than are available.
Hexadecimal: The base-16 number system, using 0 to 9 and A to F.
Character set: A list of characters and the binary codes that represent them.
ASCII: A character set that uses 7 bits for 128 characters.
Unicode: A character set with codes for many more characters, including emoji.
Pixel: A single dot of colour in an image.
Colour depth: The number of bits used for the colour of each pixel.
Resolution: The number of pixels in an image.