We need system in almost every aspect of human life to prepare meals, maintain cars and to travel to work or school. An information system, however, is responsible for the collection, processing and overall management and distribution of information.
Computers and communication devices are used to do this. They can manage large amounts of information at a faster rate than manual systems, such as filing, sorting and mailing.
When choosing a computer information system for a particular application, you need to consider:
- What hardware is used, such as input, storage and output devices
- What software is used, including the choice of custom-written, general purpose and specialised software
- What processing takes place
- What human-computer interface is used
- Which people are involved and what work they do
- What data is required.
You can now apply this knowledge to decide which systems and application are appropriate in various computer-related fields. Some examples are illustrated in this chapter, such as commerce, manufacturing, science and technology, education, law enforcement, and recreation. You should first recognise the advantages and disadvantages of computerised information systems.
Types of computer system
Computer information system can be chosen to suit different users and tasks.
- Single-user: only one person at a time can use the computer system and have access to all the computer’s resources. Example of systems for single users are windows 2000 and MS DOS.
- Multi-user: many users can access the computer system simultaneously, each having different access rights and share of the resources. Multi-user systems usually require user names and passwords. Examples of these are UNIX, Linux, and Windows NT.
- Single-tasking: only one program can be used at any one time. While that program is runing, it controls all the system resources, even if it does not need them.
- Multi-tasking: a method of organising computer system so that several different tasks or application can be accessed at the same time. The processor divides its time between tasks. While a user is entering data at the keyboard, for example, the processor will be dedicated to a different task there is no point at which the processor is simply waiting for input to be completed.
There are also different types of computers, each with unique characteristics.
- Personal computer: also called simply a computer, it fits on an office desk. It is easy to buy, upgrade and maintain. Its tasks are for a single user. Memory size are increasing but it is not uncommon to find primary storage sizes of 1.5 GB (RAM) and hard disk sizes of 20 Gb. Processors are commonly 128-bit working at speeds of 1.7 GHz.Their main use is for office-type work, games and entertainment, Internet acess and data communication including electronic mail. They can, however, be linked in a network with more powerful computers.
- Portable computer: These are also called laptops or notebooks. They are similar to personal computers but are smaller, lighter and contain batteries so that they are not restricted to being connected to electrical outlets. They are often slightly more expensive than personal computers.
- Mainframes: Mainframe are very large capacity computers with several central processors. They also have additional dedicated processors to control data flow between peripherals and communication devices. mainframes need a carefully controlled environment, power supply protection and air conditioning. mainframes are multi-tasking, multi-user and are usually the centre of a large network.Users may connect to the mainframe remotely and only the system administrator will have direct access the the physical computer. Primary storage and secondary storage are therefore extremely large. Organisations such as banks, airline, universities and government department use mainframes they are very expensive to buy, and need fulltime staff for their operations, maintenance and upgrades.
- Network computers: These include network servers, such as file servers, print servers, mail servers. These machines are built for reliability but their specifications will depend on their use. For example, file servers may have very large backing store sizes for the file system but may only require a small primary store for the operating system. Servers are not usually accessible directly by anyone except the network administrators but rather provide services to other computers when required. Servers are often more expensive than and personal computers and are housed in secure environment. They are not as big and specialised as mainframes.
- Supercomputers: these are dedicated mainframes that may be specifically designed for task such as performing highly complex and repetitive calculations. They have huge memory sizes, are very expensive and are complicated to use and maintain. They often have their own unique operation system and will require users to write their own programs for their use. The Cray T3E supercomputer is used to predict weather patterns.