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In the real world, we work with numbers based on ten, because we have ten digits on our hands. A computer works with numbers based on two. The reason for this is that it is easy to represent two states, using a voltage which is either on or off. Off is called ‘Logic Zero’ and On is called ‘Logic One’.
This ‘Base 2’ numbering system is called ‘Binary’. The smallest digit is the ‘Binary Digit’ or ‘Bit’.
Back in the real world, we still need our decimal numbers, so by grouping bits together, it is possible to persuade computers to work in decimal. Each bit added to the group multiplies the the number of combinations possible by a factor of two. When eight bits are grouped, this is referred to as a ‘Byte’ (four bits is called a ‘Nibble’-yes, seriously!).
To calculate how many combinations are possible in binary, raise 2 to the power of the number of bits, or: 2 times 2 times 2 times 2..... Repeated for the number of bits required. ‘To the power of’ may be written using the ‘caret’ symbol “^”, e.g. 2^3 = 2x2x2 (=8).
To put what I have just said into words, a byte has eight bits, so that gives: 2^8; This gives a result of 256 combinations. Try it on a calculator: 2x2x2x2x2x2x2x2 = 256. A nibble (4 bits) = 16.
So where is all this leading? Well, in MIDI, music is represented in this numeric form, so it is useful to know how the information is stored.
The following animated table shows the bits in a byte. The right hand bit is called the ‘Least Significant Bit’ or ‘LSB’ and the left bit is called the ‘Most Significant Bit’ or ‘MSB’. The diagram also shows the decimal ‘weight’ of each bit, used to calculate the equivalent decimal number. This table could be extended if you required more bits. All that you need to do is double the previous bit weight, i.e. from 128, the next bits would be: 256, 512, 1024, etc. The table updates every 15 seconds. Extra information will appear, if you hold the mouse over sections of the table (moving the mouse slightly will display the message longer).
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