2. Classification Of Computer
• Until recently computers were classifieds as microcomputers, super
minicomputers, mainframes, and supercomputers. Technology, however, has
changed and this classification is no more relevant. Today all computers used
microprocessors as their CPU. Thus classification is possible only through their
mode of use. Based on mode of use we can classify computers as Palms,
Laptop PCs, Desktop PCs and Workstations. Based on interconnected
computers we can classify computers we can classify them as distributed
computers and parallel computers.
3. Palm PCs or Simputer
• With miniaturization and high-density packing of
transistor on a chip, computers with capabilities
nearly that of PCs which can be held in a palm have
emerged. Palm accept handwritten inputs using an
electronic pen which can be used to write on a Palm’s
screen (besides a tiny keyboard), have small disk storage and can be
connected to a wireless network. One has to train the system on the user’s
handwriting before it can be used as a mobile phone, Fax, and e-mail
machine. A version of Microsoft operating system called Windows-CE is
available for Palm.An Indian initiative to meet the needs of rural population
of developing countries is called Simputer. Simputer is a mobile handheld
computer with input through icons on a touch sensitive overly on the LCD
display panel. A unique feature of Simputer is the use of free open source OS
called GNU/Linux. The cost of ownership is thus low as there is no software
cost for OS. Another unique feature of Simputer not found in Palm, is a
smart card reader/writer, which increases the functionality of the Simputer
including possibility of personalization of a single Simputer for several users.
4. Laptop PCs:
• Laptop PCs (also known as notebook computers) are portable
computers weighing around 2 kgs. They have a keyboard, flat
screen liquid crystal display, and a Pentium or Power PC processor.
Colour displays are available. They normally run using WINDOWS
OS. Laptops come with hard disk (around 40 GB), CDROM and
floppy disk. They should run with batteries and are thus designed to
conserve energy by using power efficient chips. Many Laptops can
be connected to a network. There is a trend towards providing
wireless connectivity to Laptops so that they can read files from
large stationary computers. The most common use of Laptop
computers is used for word processing, and spreadsheet
computing. As Laptops use miniature components which have to
consume low power and have to be packaged in small volumes.
5. Personal Computers (PCs)
• The most popular PCs are desktop machines. Early PCs had Intel 8088
microprocessors as their CPU. Currently (2004), Intel Dual Core is the most
popular processor. The machines made by IBM are called IBM PCs. Other
manufacturers use IBM’s specifications and design their own PCs. They are
known as IBM compatible PCs. IBM PCs mostly use MS-Windows,
WINDOWS –XP or GNU/Linux as Operating System. IBM PCs, nowadays
(2004) have 64 to 256 MB main memory, 40 to 80 GB of Hard Disk and a
floppy disk or flash ROM. Besides these a 650 MB CDROM is also provided
in PCs intended for multimedia use. Another company called Apple also
makes pCs. Apple PCs are known as Apple Macintosh. They use Apple’s
proprietary OS, which is designed for simplicity of use. Apple Macintosh
machines used Motorola 68030 microprocessors but now use Power PC
603 processor. IBM PCs are today the most popular computers with
millions of them in use throughout the world.
6. Workstations:
• Workstations are also desktop machines. They are, however, more powerful
providing processorspeeds about 10 times that of PCs. Most workstations have
a large colour video display unit (19 inch monitors). Normally they have main
memory of around 256 MB to 4 GB and Hard Disk of 80 to 320 GB. Workstations
normally use RISC processors such as MIPS (SIG), RIOS (IBM), SPARC (SUN), or
PA-RISC (HP). Some manufacturers of Workstations are Silicon Graphics (SIG),
IBM, SUN Microsystems and Hewlett Packard (HP). The standard Operating
System of Workstations is UNIX and its derivatives such as AIX (IBM), Solaris
(SUN), and HP-UX (HP). Very good graphics facilities and large video screens are
provided by most Workstations. A system called X WINDOWS is provided by
Workstations to display the status of multiple processes during their execution.
Most Workstations have built-in hardware to connect to a Local Area Network
(LAN). Workstations are used for executing numeric and graphic intensive
applications such as those, which arise in Computer Aided Design, simulation of
complex systems and visualizing the results of simulation.
7. Servers
• While manufacturers such as IBM, SUN and Silicon Graphics have been
manufacturing high performance workstations the speed of Intel Pentium
Processors has been going up. In 2004, Pentium with clock speed 3 GHz
are available. They can support several GB main memories. Thus the
difference between high end PCs and Workstations is vanishing. Today
companies such as SUN make Intel based workstations.While Workstations
are characterized by high performance processors with large screens for
interactive programming, servers are used for specific purpose such as
high performance numerical computing (called compute server), web
page hosting, database store, printing etc. interactive large screens are not
necessary. Compute servers have performance processors with large main
memory, database servers have big on-line disk storage (100s of GB) and
print servers support several high speed printers.
8. Mainframes Computers
• There are organizations such as banks and insurance companies
process large number of transactions on-line. They require
computers with very large disks to store several Terabytes of data
and transfer data from disk to main memory at several hundred
Megabytes/sec. The processing power needed from such
computers is hundred million transactions per second. These
computers are much bigger and faster than workstations and
several hundred times more expensive. They normally use
proprietary operating systems, which usually provide high
expensive services such as user accounting, file security and
control. They are normally much more reliable when compared to
Operating System on PCs. These types of computers are called
mainframes. These are a few manufacturers of mainframes (e.g.,
IBM and Hitachi). The number of mainframe users has reduced as
many organizations are rewriting their systems to use networks of
powerful workstations.
9. Supercomputers
• Supercomputers are the fastest computers available at any given time and
are normally used to solve problems, which require intensive numerical
computations. Examples of such problems are numerical weather
prediction, designing supersonic aircrafts, design of drugs and modeling
complex molecules. All of these problems require around
10^16calculations to be performed. These problems will be solved in
about 3 hours by a computer, which can carry out a trillion floating point
calculations per second. Such a computer is classifieds as supercomputer
today (2004). By about the year 2006 computers which can carry out
10^15 floating point operations per second on 64 bit floating point
numbers would be available and would be the ones which be called
supercomputers. Interconnecting several high speed computers and
programming them to work cooperatively to solve problems build
supercomputers.
10. • . Recently applications of supercomputers have expanded beyond
scientific computing, they are now used to analyze large commercial
database, produced animated movies and play games such as chess.
Besides arithmetic speed, a computer to be classified as a supercomputer
should have a large main memory of around 16 GB and a secondary
memory of 1000 GB. The speed of transfer of data from secondary
memory to the main memory should be at least a tenth of the memory to
CPU data transfer speed. All supercomputers use parallelism to achieve
their speed. In Sec. 12.9 we discuss the organization of parallel computers
