MY_ASSIGNMNT

DATA TYPES
a.)What are they?
A data type in a programming language is a set of data with values having predefined characteristics. Examples of data types are: integer, floating point unit number, character, string, and pointer. Usually, a limited number of such data types come built into a language. The language usually specifies the range of values for a given data type, how the values are processed by the computer, and how they are stored.
---3 different DBMS Software---


3 Examples of data types in DBMS

STRING

• Character string, has a fixed size up to 64 Kbytes.

POINTER

• This field is a pointer to a record in another Class. Physically it contains the sub-Class record number. Size can be from 1 to 4 bytes. Having pointers makes ConteXt somewhat different than traditional DBMS systems. Connection between tables in relational databases is done through the common indexing of two tables with common keys. In this case, the keys must be present in both tables, which means size overhead. To perform search for related records in two tables both indexes are needed. In ConteXt there is no need to search. The number of a record in a sub Class is contained in the field of the main Class. (Terms "main Class" and "sub-Class" in the future will only be used for clarity, but in reality all Classs in ConteXt are equal.) Since there are no keys, the performance is much better In this case it is important to understand that fields are not linked together, only records. The field simply points to a record.

VARIANT

• It is an even more exotic field type. The standard POINTER field can only link two Classs. The value of a POINTER field is the sub-Class record number. The name of this sub Class is contained in the header of the main Class. At times there is a need to have the POINTER to several different Class. EXAMPLE: There is a "CHECK" Class with "PAY_TO" field. A check made out for supplies will have the pointer point to "SUPPLIES", whereas a payment for employee salaries will use the pointer to "STAFF" Class, etc. VARIANT consists of two ponters, the first points to a name of the sub Class the second to a record in this Class.