What is a Digital Information
Definition
Digital :
Derived from the capacity to count on fingers (latin : digitalis).
By extension, DIGITAL describes electronic technology that manages (stores, modifies, etc...) data in terms of two states.
In opposition, analog technology manage information by changing the amplitude or the frequency.
When we talk about a digital value, it implies that this value could be used by a digital device like a computer.
Numerical :
Used to talk about counted values. It's the generic word for a value.
A digital value is also a numerical value, but a numerical value is not necessarily a digital value.
What is in a computer's mind ?
Binary states
There can be no ambiguity in a digital device.
All the elementary digital information have just two possibilities :
- FALSE or TRUE
- OPEN or CLOSED
Actually, all digital devices have a logical behavior, and both states are defined as "0" and "1".
So it's possible to use base-two which has just two numbers.... 0 and 1.
Example 1:
The switch position :
Switch position |
Binary value |
OFF |
0 |
ON |
1 |
Example 2 :
John is 1,8meter tall.
Is John taller than 1meter ?
The answer is YES
John=1
This binary unit is called BIT (from the contraction of BInary digiT).
More than two.....
In this last example, we can see that John's height is not very precise.
Most of the time, it's necessary to be more precise but, with a digital conversion we always lose information.
To have 4 steps in this problematic, we need 2 bit. An so we can give a more precise value : John's height is between 1,5m and 2m. Every value represents a range of 50cm. |
|
To have 8 steps we need 3 bit. Every value represents a range of 25cm. |
|
The use of more than one bit gives us the possibility to define more than two pieces of information.
Number of bit |
Number of possibilities |
1 |
2 |
2 |
4 |
3 |
8 |
4 |
16 |
n |
2n |
A binary value with more than one bit is called a Binary Word or a Word.
An eight bit word is called a BYTE.
A n binary word has 2n ( 2 to the power of n) different values from 0 to 2n-1
Let' come back to our example :
John is 180cm tall.
The easiest way to be more precise is to convert 180 in a binary word. In this case we have centimeter-level precision.
With n=8, the different possibilities are going from 0 to 255