Bits
What is a bit?
A bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as either “1” or “0”, but other representations such as true/false are also widely used.
Why use bits?
The answer is not simple, but has to do with practicality of electronics. The primary electrical block of all digital systems is the transistor. Checking if a state of a transistor, (is it on or off) can be done fairly easily and reliably. In order to build systems with more states for example three states, it would be necessary to accurately determine a state between on and off.
Bits and Transistors
Digital devices such as computers may contain billions of transistors. These transistors are in turn used to represent bits of information. Depending on architecture of the device, it may take six transistors to store one bit of data.
Bits and Binary
Since each bit can only represent two states (0 and 1) they are not very useful by themselves. By collecting bits into larger groups though, we can represent much larger numbers. For example, two bits can represent four states as shown in the table below. Three bits can represent 8 states and so on.
bit0 |
bit1 |
state |
|---|---|---|
0 |
0 |
0 |
1 |
0 |
1 |
0 |
1 |
2 |
1 |
1 |
3 |
It is useful to note that the number of possible states grows rapidly. Sixteen bits can represent 65,536 states. Sixty-four bits can represent over 18 quintillion states, a number so large it is hard to comprehend.
Exercise
In your notebook write down how many states can be represented by four bits.