Only two symbols are necessary to represent an information (a numbre, a letter etc. ). For Example the Morse Alphabet, created in the second half of 1800 for the informations' telegraphic transmission,is based on two symbols "point" and "line", which opportunely connected, represent all the letters and all the digits.

This possibility is exploited in the calculation machine too,which is a machine composed by some elementary members which is possible to find in only two different conditions: in a circuit the current passes or doesn't pass,an electronic tube is on or off, a ferromagnetic ring is magnetized on a side or on an other one.

In order that the calculation machine sets the informations, the two possible conditions of its members are shown conventionally by 1 and 0, and the numbers, the letters and the special characters are represented by the combination of some 1 and 0.

This code is called "binary" and the two symbols 1 and 0 are also called "BIT" (from English Binary Digit).
The numerical system normally used by man is the decimal one, which adopts ten symbols.

The place occupied by the digits represents the unity, the tens , the hundreds,etc., it means the growing powers of ten.
The numerical binary system, which is adopted by the calculation machines, uses only two symbols (1 and 0) and the place which is occupied by them, represents the growing powers of two.

When it moves on the left of a column, each digit's value doesn't increase of ten times, as in the decimal system, but of two times. In both the decimal system and the binary one, in one number the value of each digit depends on the position taken in the number's ambit according to the formula :

The value (V) is given by the digit (C) multiplied the base (B) raised to the position (P) which is occupied by the digit in the number's ambit, beginning from the 0 position and running the number from right towards left.

For example the binary 1001 is the decimal 9.

Besides the numbers, even the letters, the punctuation marks and some other symbols with a special meaning can be represented by the two digits 1 and 0, through the use of codes which are based on the basic binary system.
As 1 and 0 means for the machine the presence or absence of an electric impulse, it is possible communicate and recalls the calculation machine through electric marks all the informations and the necessary directions to execute the demanded operations.

The adoption of the numerical binary system has more advantages for the calculation machine than the decimal system, infact it is possible to distnguish an electronic mark only between the possible two, rather than among ten, and it is also possible to use the rules of the binary arithmetic which is more simple than the decimal one.

To execute the various arithmetical and logic operations the calculation machine bases itself on few and simple rules known as "Boole algebra", from the name of the English mathematician who formulated them for the binary systems in the second half of 1800.

The machine's calculus circuits connect various electric impulses which are received to respect the binary rules of the sum, of the multiplication etc.

The multiplications are executed by the calculation machine like a series of following , sums, the subtractions and the divisions are trasformed into sums by special contrivances: using the binary system, the machine doesn't execute anything more complicated than 1 + 1.

Executing the subtractions, tha calculation machine is able to develop the logic function of the decision, which is nothing else than another comparison between two sizes, it means a subtraction.

According to this subtraction's results, which can be also a positive number, a negative number or nought, the calculation machine can be predisposed to execute alternate operations.