Hard disk-main internal storage. Rage capacity-range from KGB to 1 Gob! Floppy disk-3. 5 inch 1. 44 MBA-very small capacity Magnetic tape-used to backup large amounts of data-cheap as well! Access time is slow because it has to run through whole disc to find something. Optical disks have fast access time. CD-ROOMS-Oldest type-iamb CD-Or’s;sold as blanks-data can be written only once to it. CD-Row’s-most popular. RAW stands for read and write. DVD-17 KGB ZIP disks-larger, thicker-iamb
- Operating systems
- Enable applications to run
- Enables software to communicate with systems hardware.
- It manages system resources
- Monitors performance of system
- Prompts error messages.
Multi tasking means an SO can run more than one program at a time Basic systems that are not multi tasking are called single program mode Ox’s. User interfaces Can be command driven-blank screen and commands and code used. Can be menu driven- headings and menus Most common is GIG-II-graphical user interface-combines menu driven and cons- Guy’s are known as WIMPS-windows, icons, menus, pointers Data capture Data capture turns info into data Automatic data capture-is fast and accurate BUT manual data capture- is necessary sometimes, and it’s cheaper!
Data validation and verification Validation-4 checks Range check-checks data is in specified range Presence check-makes sure data is present Check digit-check that numerical data is accurate Data type-checks that text is not where numbers are meant to be. Verification-2 checks Proof reading-read it and make sure that its accurate Double-entry-data entered twice and compared. Validation problems- mistakes may be allowed if carried out wrong and only makes sure that data is right type-NOT ACCURATE. Verification problems-double entry is time consuming-expensive and proof reading is time consuming and does not eliminate human error.
Data processing Real time processing does it instantly Batch processing-all in one go Transaction processing-one off specials Interactive processing-talk to the computer Access to data Serial access-records are stored one after another in creation order Sequential access-records are stored one after another AC. To sensible order Direct access-can go to record directly Implementation and evaluation 3 types of implementation- Direct-straight away and old system goes down but bugs not picked up in testing-bad news!
Phased-different parts are introduced one at a time Old system is kept running Parallel-new system is introduced in one go BUT old system stays New system can be tested quickly but all tasks need to be done twice. Evaluation just checks that the system meets all objectives DIP SOFTWARE-is good because it creates pro. Looking documents and the layout can be changed more easily than word processors and the user can intro the number of pages more easily than a word processor INTERNET The Internet is basically a very big WAN.