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Information Systems
Module1
| Question | Answer |
|---|---|
| Data | Data is a description of an item of event. Data has no real meaning. Data is raw facts. |
| Information | Information is the result of data processing. In other words - information is processed data. This is useful to the user and forms the basis for decisions. |
| Knowledge | When information that is gathered, interpreted and analyzed and conclusions are reached, knowledge is gained. |
| Data processing activities | data processing consists of the following processes, recording of data, manipulation of data, classification of data, the saving of data and output of processed data (information). |
| Computer programs | A program consists of instructions that is written in a computer language and that is executed by a computer to perform a specific task. |
| Programming languages | Machine language - A program must be available in machine-readable language before a computer can execute the instructions. Machine language is expressed in binary format and consists of zeros and ones. |
| Assembler | To ease the troubles in programming, an instruction set was developed in the early 50's which replaced the machine language codes with symbolic processing codes which were more manageable and easier to use. |
| High-level language | High-level languages are easier to use and understand. These languages are applied in different fields of programming. |
| Compilers | A compiler translates the source code of program to object code. The programmer enters the source code by using a high-level kanguage such as Pascal. |
| Interpreters | In the case of some high-level languages, such as BASIC, the source code is never translated into object code. |
| Some better known high-level languages | BASIC (Beginner's All-purpose Symbolic Instruction Code) is a popular language, which is widely used and easy to learn |
| FORTRAN | (FOrmula TRANslator) is a language developed for the solving of scientific problems. |
| COBOL | (Common Business Oriented Language) was developed for business applications. |
| PL/1 (Programming Language 1) | is a multi-purpose high-level language and can be used on mainframe computers. |
| PASCAL (named after the French mathematician Blaise Pascal) | can easily be mastered and is easy to use in a program development. |
| Very high-level languages/forth generation languages | Fourth generation languages are also known as 'no procedure languages'. The programmer states the tasks to be performed. Examples are C, CC+ AND VISUAL-BASIC, JAVA. |
| Computer files | A computer file is similar to a paper file in a filing cabinet. The smallest unit of data is a field. |
| Classification of files | |
| Master files | Data in a master file is of a reasonable permanent nature. |
| Transaction files | A transaction file contains data about a daily, weekly or monthly occurrence like a worker's time worked or sales of a salesman during a month. |
| Table files | The content of these files is of a permanent nature and is used as a reference in processing. |
| File processing activities | |
| Enquiries | Enquiries to a file are done by using a key field. |
| File maintainance | means the adding of new records, the deleting of old records and the editing of information such as SURNAME of a employee who marries> |
| Updating | takes place when the data in the transaction file is used to write recent transactions to a master file. |
| File organisation | |
| Sequential files | Files in which records are sorted according to a key field are called sequential files> |
| Random access files | With direct access no reference is made to other records in the file when a record enquiry is made or a record is updated. |
| Index sequential access | In these files an index is used to determine the location of a record in a file. |
| Methods of processing | |
| Batch processing | With batch processing the data of the transactions are accumulated in batches and processed at a later stage. |
| Online entry | With online entry the location where the transaction originates may be far away from the mainframe computer. |
| Real-time processing (on-line update) | Real-time processing is also called interactive processing. Processing takes place immediately after the transaction took place and the results of processing are available immediately. |
| Data Communication and networks | |
| Components of a data communication system | |
| 1.Central processor and input/output storage devices | In an on-line system, every computer must have a reliable, powerful central processor because large volumes of data must be processed at the same time. |
| 2.People | In any information system there are people who can make decisions based on the information. |
| 3. Communication channels | |
| Local terminal | When a terminal is situated within the same building as the central computer, we call it a local area network (LAN). |
| Distant terminal | The terminal is linked to the main computer through telephone lines. |
| Modems | A modem (MOdulator DEModulator) converts the digital signals from the source computer to analogue signals, which can be transferred along the telephone line. |
| Microwave channels | Microwave channels are used for the transfer of radio signals between microwave towers, which are provided by TELKOM |
| Satellite transmission | With satellite transmission the signals from the computer are relayed as low frequency radio signals to a ground station. which transmits it to a satellite somewhere in space. |
| Optical fibre cable | It consists of a glass fibre encapsulated in cladding. |
| 4. Communication control devices | |
| Multiplexors | Multiplexors gather the signals from a number of terminals and send it across one communication line. |
| Concentrators | A concentrator performs the same function as a multiplexor but is more sophisticated. |
| Communication controllers | Communication controllers are usually micro or mini computers, which handles data communication facilities. |
| Front-end processors | A front-end processor is placed near the central computer. |
| 5. Hardware connected to the host computer | A terminal consists of a monitor and a keyboard. |
| 6. Software | Special operating system software is necessary to control data communication. |
| Types of networks | A network is more than the sum of its parts. |
| Local area Network (LAN) | A local area network is a number of personal computers linked to a central computer, the file saver. The computers on a LAN are linked through co axle cables. |
| Campus Area Network | A network that connects two or more LANs but that is limited to a specific geographical area such as a university or college campus. |
| Wide Area Network (WAN) | Wide area networks cover a larger geographical area than local area networks. A WAN wil have a more powerful computer as a server with more computers linked to it as in the case of a LAN. |
| Metropolitan Area Networks (MAN) | This network is used to link buildings in the same city or town. |
| Public Networks | Public networks allow communication between computers nationally and internationally. This allows the use of electronic mail. |
| Network Topologies | The network topology describes the method used to do the physical wiring of the network. The mains ones are BUS, STAR and RING. |
| Security in the computer environment | |
| Physical Security | |
| 1. Firefighting equipment | It is important to guard against overloading of electricity points and ensure that connecting wires are well out of the way. |
| 2. Emergency plan | For lanrge companies it may be necessary to have a backup installation to which operations can be switched in case of damage to the computer equipment of the company. |
| 3. Clean enviroment | Modern personal computer hardware can function in a normal office enviroment, but it is necessary to prevent it from dust and smoke. |
| 4. Duplication of hardware | Some hardware is so important to the installation that it may be necessary to keep back up equipment available in the case of failure. |
| 5. Insurance | Computer hardware can be covered under a normal short term insurance policy. |
| 6.Uninterruptible Power Supply (UPS) | In an office enviroment a UPS (Uninterruptible Power Supply) is necessary to avoid data lost during an electricity failure and to protect hardware against power surges. |
| Computer Fraud | It is of vital importance to implement the necessary controls in the computer enviroment to prevent members from manipulating data for their own benefit. |
| 1. Rotation of jobs | Employees should change jobs at random intervals. |
| 2. Passwords | Access to information must be allowed to certain staff members only. |
| 3. Separation of duties | The duties in the operating, data control and programming section of the computer enviroment must be separated. |
| 4. Supervision | No person should be allowed to work in the computer room without supervision. |
| 5. Physical access control | In large insatllations, access to the computer room must be limited to authorize members only. |
| 6. Computer staff must take leave when leave is due | Back up staff will then be used to perform the task of the person on leave. |
| 7. System logs | System logs must be kept to record all computer activites. |
| Acquiring computers for business concerns |
Created by:
Sindisiwe