Information representation options in the Computer
All information (data) is provided in the form of binary codes. For convenience of operation the following terms designating sets of binary places (tab. 1.1) are entered. These terms are normally used as units of measure of information volumes, storable or processed in a computer.
Table 1.1Binary sets
Quantity of binary places in group
Unit of measurement name
The sequence of several bits or bytes is often called the Bit data field in number (in a word, in the field, etc.) They are numbered from right to left, since 0th discharge.
In the PC fields of constant and variable length can be processed. Numbers from the fixed comma have a format of a word and a half-word, number from a floating comma a format of a double and expanded word more often. Fields of variable length can have any size from 0 to 256 bytes, but surely equal to an integral number of bytes.
Binary-coded decimal numbers can be provided to the PC by fields of variable length: in the so-called packed and unpacked formats.
The continuous and discrete information
To transfer the message from the source to the receiver the material substance information medium is necessary. The message transferred by means of the carrier is called a signal. Generally the signal is a physical process changing in time. Such process can contain different characteristics (for example, by transmission of electrical signals tension and current intensity can change). The characteristic used for submission of messages is called the signal parameter.
When the parameter of a signal accepts serial in time a finite number of values (thus all of them can be enumerated), the signal is called the discrete, and the message transferred by means of such signals the discrete message. Information transferred by a source, in this case also is called the discrete. If the source works out the continuous message (respectively signal parameter the continuous function from time), the relevant information is called the continuous.
The units of measure of information serve for information volume measurement the value calculated logarithmic. It means that when some objects are considered as one, the quantity of possible statuses is multiplied, and the number of information develops. It is not important if there is a speech about random variables in mathematician, registers of digital memory in technique or quantum systems in physics.
More often measurement of information concerns the volume of computer memory and the data volume transferred on inter-chip digital links. The whole number of bits responds the quantity of statuses equal to powers of the number «two».
The special name has 4 bits nibble (half-byte, a tetrad, four binary places) which contain in itself number of information containing in one hexadecimal digit.
In the order of popular numbers in information is 8 bits or byte. The increasing information volumes calculated in computer technologies are directly given to byte (instead of bit). Such values as a machine word, etc., bytes making as units of measure are never used.