• Computers are complex machines that work by storing the simplest of values:
• 0 (also known as false or off)
• 1 (also known as true or on)
• This is called binary or base-2.
• This unit won't teach you lots about binary, but there are other units that will.
• For now you just need to know that computers use binary to store data.
• In ICT we call a single 0 or 1 a bit (short form binary digit)
• If you understand binary, you will get the following joke:

• Don't worry if you don't get it...you might one day!

• In computers, groups of 8 bits are stored together in a Byte.
• b stands for bit, B stands for Byte.
• A byte will look something like this:
• 10010111
• A byte can be used to:
• Store a number of 0 to 255.
• Store a letter of the alphabet, and some other special symbols like !, ? or @.

• ASCII (pronounced as-key) is a system that computers use to store characters (letters, numbers, special symbols).
• Instead of storing a letter directly, ASCII stores characters as numbers.
• For example A is the number 65 and a is the number 97
• You can use the chart below to see how different characters are represented as numbers in ASCII (click for a larger version):

• I could use ASCII to write my name (Ross Parker) as follows:

82 111 115 115 32 80 97 114 107 101 114

• Take some time now to write your name in ASCII.
• However, as computers can only store binary, a computer would store my name as:

01010010 01101111 01110011 01110011 00100000 01010000 01100001 01110010 01101011 01100101 01110010

• Take a little more time to write your name in ASCII in binary using this online converter.

• Because computers store so much information, we often don't count in bytes, but use groups of bytes.
• You may have heard of a gigabyte, or other groups such as kilobytes and megabytes.
• The table below shows what these things are:

1 bit (b) = a single 0 or 1

1 byte (B) = 8 bits

1 kilobyte (KB) = 1024 bytes

1 megabyte (MB) = 1024 kilobytes

1 gigabyte (GB) = 1024 megabytes

• This means that a gigabyte is a collection of 8,589,934,592 bits.
• Or 1 x 8 x 1024 x 1024 x1024
• That's a lot of data!

• If you want some even bigger numbers:

  1 terabyte (TB) = 1024 gigabyte

  1 petabyte (PB) = 1024 terabytes

  1 exabyte (EB) = 1024 petabytes

  1 zettabyte (ZB) = 1024 exabytes

  1 yottabyte (YB) = 1024 zettabytes

• It is very hard to imagine how big these numbers are, but the image below might help you get a handle on the size of a petabyte:

• To show what you have learned in this unit:
• Create a Google Doc
• Give the document a title
• Add your name as author
• Write your name in ASCII using regular numbers
• Write your name in ASCII using binary numbers
• Make a guess at how many bytes of information are contained in the whole English language version of Wikipedia.
• When your Google Doc is ready, submit it as evidence of your learning in this unit.