Presentation on theme: "How data is stored. Data can be stored in paper-based systems including: Reference books Dictionaries Encyclopaedias Directories Index Files Filing systems."— Presentation transcript:
Index files: Alphabetical file systems Date order file systems Cross Indexed file systems
The data is stored systematically (e.g. alphabetically – dictionaries, encyclopaedias, telephone directories; date order – year books, almanacs). The data has a key piece of information that helps users to find what they are looking for (e.g. surname in a telephone directory, date in a year book).
Computerised data systems – also known as databases – are organised in similar ways to paper-based data systems. However because computerised data systems can handle data faster and in more flexible ways than paper-based systems, they have begun to replace many paper-based systems.
A database is a large store of information. It should set out so that it can be kept up-to-date easily. It should be easy to find the information that you need.
The information contained in a database is held in RECORDS. Each record is made up of one or more FIELDS. A FIELD contains a separate piece of information within each RECORD. A group of related RECORDS is a FILE.
There are several types of FIELD. The most common are: ALPHANUMERIC or CHARACTER TEXT - these contain letters and numbers, but the numbers can not be manipulated. NUMERIC - these numbers that can be manipulated. LOGIC – these have Yes/No or True/False answers.
Once the database has been set up, the information for each record can be added. This information can then be INTERROGATED (questions can be asked) to produce REPORTS (answers).
Medical records held at hospitals and doctors surgeries. The Police National Computer. School records held on a school SIMS (School Information Management System) system.
Information usually only needs to be entered once. Files can be linked together so that when one is up- dated all linked files are also up-dated (N.B. This is only true of RELATIONAL databases). The record structure can be altered after data has been entered. Access to data is rapid. It is difficult to lose data. Data can be validated as it is entered.
If the computer system is not working or is off- line, the database can not be accessed. Because databases contain confidential information, they must be kept secure People have to be trained to use a database if its advantages are to be exploited to the full, and this takes time and money.
A data base management system (DBMS) is a group of programs that: Allow data files to be created Allow data held in files to be altered Allow data held in files to be extracted
A DBMS also allows: Datafiles (or tables held within data files) to be linked together. Queries (or questions) to be asked of the data. Data to be added (or appended). Data to be deleted or altered. The structure to datafiles (or tables) to be altered.
A DBMS also allows: Levels of security by only allowing particular users access to each of the datafiles (or tables). Data to be imported from other computer packages (e.g. spreadsheets). Data to be exported to other computer packages (e.g. mail merge).
The processes that the database management system allows are all common file processes. The main common file processes are: File updating. Insertions. Deletions. Amendments
There are also certain tasks that must be done on a regular basis. These include creating back-up copies of the data held on the database. This needs to be done to protect the data from damage or corruption and to ensure that if damage or corruption occurs, all the data is not lost.