October 02, 2017

Data unit definition

❑ Bit : The smallest unit of information.
* 0 or 1

❑ Nibble : This represents a hexadecimal digit. A gathering of 4 bits.

❑ Byte : The smallest unit of characters. A gathering of 8 bits.

❑ Word : A gathering of bytes.
* On 80386 basis, half word : 2 bytes / full word : 4 bytes / double word : 8 bytes

❑ Field : The smallest unit of data processing.
* attribute, item

❑ Record : A gathering of related fields.
* This is Input-output unit of auxiliary memory.
* tuple, block, datapage,

❑ File : A gathering of records.

❑ Database : A gathering of files.


e.g.
- An employee information is a "field" that is name, nation, phone number etc.
- The employee's related information collection of is "record". A name record has many names of employees.
- A collection of employees' records is the employee "file".
- Not only employee "file", this company also has other "file"s like client file, order file, branch office file etc.
- And the gathered all the files is the company's "database".