Data Structures

·         Are arrangements of data items

·         Simplifies access and processing of data

·         Consider the nature of the processing

·         Can reduce the complexity of the processing required

·         Can increase the processing required and reduce the software’s performance

One dimensional array

·         Used to store multiple data items of the same data type

·         Each element has a unique index used to access the data

·         Used extensively in non-computing applications

·         Contain distinct countable number of elements

·         An index is an integer value used to denote a particular data item held in an array.

Record

·         Contains data items that are related but may not be of same data type

·         Used for database applications

·         Contains all the information about a particle entity

·         Each of the data items within each record is known as a field

·         Each record of the same data type is made up of the same fields

·         The data items held within these fields will most likely be different but the data type of like fields must be the same

·         Fields must be name and assigned a data type

Sequential Files

·         Used to permanently store data on secondary storage devices

·         Data can be written to a file or read from a file

·         Can only be accessed from start to finish

·         It is not possible to jump directly to a particular data item

·         OS controls access to files

·         OS needs to know the location and name of the file

·         Are continuous streams of data

·         The structure must understand the language of the file itself

·         Most programming languages include an end of file function, which returns the Boolean value True when the end of a file has been reached

·         Can be used to ensure errors do not occur

Data Dictionary

·         Includes all variable names or identifiers

·         Ensures all members of the development team are aware of terms used

·         Repository where this information is held

·         Data dictionary functions are available with most software development case tools

·         Can eliminate confusion due to duplicate identifiers

·         Includes a thorough description of each variable used by the program and each field

·         A separate data dictionary is created for each module, database and file

·         Commonly a data dictionary includes table with columns : identifier name, data type, length, scope of the variable and purpose or description