An application is a software system designed to perform a given set of operations on databases. It consists of:
- Actual programs (mainly programs, coordinating programs, menus, screens, queries, indexing, updates, reports);
- Databases.
Application execution is carried out at two levels:
Interpretation – when a program called “interpreter” take every statement of the application, it is translated into internal code and error analysis, it runs, then move to the next statement.
Eclectic – the entire application program is translated into a code compiler intermediate memory, called object code, which is subject to further processing by the editor of links to get final form, the application executable. Implementation is under OS control.
Making a database involves:
- analysis system which builds the database; 
- base structure design;
- loading data into the database;
- operation and maintenance of the database.
Actual implementation of an application involves:
- established the theme;
- analysis basis;
- design application;
- encoding application;
- testing modules;
- application implementation;
- application maintenance.
Setting the theme
The theme is determined by the recipient application, the report of activities to be modeled.
b) Analysis basis
Analysis includes identifying the types of information, linkages between them, the operations required for their management.
Result of analysis includes:
- description of input data;
- description of the data stored in the database;
- list processing performed on data;
- description information in the reports.
c) Application Design
At this stage of design data structure and program structure. Structural design software modules needed for the application detailing involves modules for creating files for data entry, processing and retrieving results, error handling, etc.. These modules are controlled and coordinated by the main program, which has the following structure:
feature program
declare global arrays
init global variables
average state general relief boot
SET PROCEDURE TO subprogramms_comon
open common files
end = False
DO WHILE running. NOT. Finally setup dialog
block CLEAR SCREEN
command displays the dialog
takes the user options
Perform a loop DO CASE CASE 10 and
1 ENDCASE CASE conditional activity, blocks
DO expression of how a command in order, if
logic. CASE 2 activity associated logical expression
DO mode 2 is true.
…
OTHER WISE
Say “invalid option”
ENDCASE
ENDDO
close common files
restore environment
CLEAR SCREEN terminating action
RETURN
d) encoding application
If c) the level of detail is pseudo type at this stage the application is written in a language specialist with the rules imposed by it.
e) testing modules
At this stage check the modules, it detects and corrects errors, is analyzed in extreme cases, designing tests.
f) Implementation Application
Builds final application form by the gradual integration of functional modules tested.
g) Application Maintenance
Remove user errors reported during the warranty period, is modernized and updated software.
Users of a database
The users of a database can be:
Lay users (conversational) which provides a form of communication with the database close to everyday speech;
Users specialists who know the database structure;
The database administrator is a particular user, which defines the base operation objectives, shared user access rights, developing the concept of projects database, responsible for all activities and operations on the database, etc. help define user requirements.
Database Languages
In the DBMS, reporting functions and data manipulation are performed using different languages.
a) data definition languages (LDD)
LDD functions are:
- done defining entities and attributes by name, form of storage, length; 
- specify relationships between data and strategies for access to them;
- establish criteria Privacy differentiated;
- defines automatic data validation criteria used.
b) Languages for data manipulation (DML)
Operations on databases require a specialized language, the commands are expressed by sentences that describe actions on the base.
A command has the following structure:
operation, which can be arithmetic or logical, editing, extracting, opening, closing, handling (input, add, delete etc.).
selection criteria (for, while, Where etc.).
access mode (sequential, indexed etc.).
editing form.
c) Data Control Languages (LCD)
Control of a database involves:
- ensuring the confidentiality and integrity of data;
- save information in case of failure;
- obtain performance;
- resolve competition issues.
d) The universal language
A universal language is rarely used for managing a database.
The interface between the user and the DBMS is done in two ways:
With an appeal mechanism inserted into the application program. This mechanism may be a CALL or another keyword. A DBMS that allows this type of mechanism is called DBMS with host language;
through special orders, used independently. In this case, the DBMS is called autonomous. There is, however, a special interface, which is able to interpret language commands calls.
