2.2. Types of Computer Systems

Today computer systems are available in different sizes, shapes and computing
capabilities. Rapid hardware, software development and increasing end user needs
drives the emergence of new models of computers from the smallest hand-held personal
digital assistant or cell phone combinations to the largest multiple CPU mainframe for the
enterprise.

Hand Held Computers
A single user computer that provides ease of portability because of its small size.
These systems often include a variety of software and communication capabilities. Most
are compatible with and can communicate with desktop computers over wireless
networks.

Portable Computers
Can be carried easily. – laptops, note books, tablet computers.

Thin Client
A low-cost, centrally managed computer with essential but limited capabilities and no
extra drives. Have limited capabilities and perform only essential applications and
therefore remain “thin” in terms of the client applications they include.

Desktop Computers
A desktop computer is a personal computer (PC) in a form intended for regular use at a
single location, as opposed to a mobile laptop or portable computer.
Can provide sufficient memory and storage for most business computing tasks.

Workstations
A workstation is a high-end microcomputer designed for technical or scientific
applications. Intended primarily to be used by one person at a time, they are commonly
connected to a local area network and run multi-user operating systems. The term
workstation has also been used to refer to a mainframe computer terminal or a PC
connected to a network.

Servers
A computer designed for a specific task, such as network or Internet applications.
Typically have large memory and storage capabilities, along with fast and efficient
communication abilities.

Mainframe Computer Systems
Mainframe systems are large, fast and powerful computer systems shared by dozens or
even hundreds of concurrent users over a network. These can process thousands of
million instructions per second (MIPS). They have got large primary storage capacity
(main memory capacity can range from hundreds of megabytes to many gigabytes of
primary storage). Mainframe systems are much more costly than micro and mid range
systems.

The mainframe computer must reside in a data centre with special heating, venting and
air conditioning equipment to control the temperature, humidity, and dust levels around
the computer. During the last few years their size has reduced which in turn has reduced
air-conditioning needs, electrical power consumption and floor space requirements and
thus their acquisition and operating costs.
The role of mainframe is changing as lower-cost, single user computers become
increasingly powerful. Many jobs that were previously carried out using mainframes have
migrated to smaller, less expensive computers. This process of migration is known as
computer downsizing.

The new role of mainframes involve handling of information processing needs of major
corporations and government agencies with high transaction processing volumes or
complex computational problems. Mainframes have the ability to process tens and
thousands of daily queries necessary to provide data to decision support systems.
For example mainframes are used for high volume transaction processing and customer
inquiry processing in major international banks, airlines, oil companies and other large
corporations. Also, these systems are used for computation-intensive applications such
as analyzing seismic data from oil field explorations or simulating flight conditions in
aircraft designing.

Furthermore, mainframes provide large storage capabilities including storing of backup
files and databases created else ware. These systems are also becoming a popular
business computing platform for data mining and warehousing and electronic commerce
applications.

Supercomputer Systems
Supercomputers are the most powerful computer systems, with the fastest processing
speeds. They are designed for applications that require extensive and rapid
computational capabilities. Supercomputers which are extremely costly cannot be
afforded by many organizations.

Supercomputers were originally used primarily by government agencies to perform high
speed numerical calculations needed in global weather forecasting, military applications,
and computational cosmology etc. However, due to the decreasing costs and improving
performance of these systems, they are being more widely used in commercial
applications.

Supercomputers use parallel processing architectures of interconnected
microprocessors. They can easily perform arithmetic calculations. They are capable of
calculating in teraflops, which use massively parallel processing.