Testing

Error occur because commands haven't not been entered or use correctly. Everything is flawed.

Syntax errors are errors that are to do with how code is entered such as typos.

Logical errors are errors where the syntax is correct but the logic in the problem is wrong, such as a  program where dividing by 0 occurs.


Test data.
Valid= test data that represents typical input into the valid system.
Valid extreme= test data that is valid but at the extreme end of the range of acceptable.
Invalid= Test data that is out of range and should be rejected.
Invalid extreme= test data that is invalid but only just at the limit of being unacceptable
Erroneous= test data that should be rejected because it is the wrong type of input.
                  

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   




































































                                                                                                 
                                                  

Databases

A database is a persistent organised store of similar data on a computer system. Persistent means it is stored in secondary storage which means it can be accessed later.


There are different models for database.









Key terms
Serial file: A file of items one after another

Sequential File: A serial file in order

Entity: Something that we store data about in a database

Record: All the data about one item in a database

Attribute: A characteristic of an entity. It becomes a field in a data table.

Field: A characteristic of something stored in a database

Indexed sequential file: A sequential file that is accessed using an index which is separate file.

Flat file database: Database consisting of only one table





A database can be used to hold information in a business e.g. employees salary, employee background. 


Key field: