ACTIVITY 3

List the Common 5 most common types of computer systems




Modern computers are electronic and process digital information. The physical machine


consists of transistors, digital circuits implemented with transistors, wires, and


mechanical components in peripheral devices used for information storage. These


physical entities are collectively called hardware. System and application programs are


called software. A general purpose computer system is a programmable machine that can


solve problems by accepting inputs and instructions on how to use these inputs. The


instructions are included in computer programs (that is, software) that normally contain


sequences of them. Graphical languages are rarely used to represent computer programs


as collections of instructions with relationships between arbitrary pairs of them.


Programs are often written in high- level languages (HLLs) that have to be translated (by


appropriate software compilers) to produce machine-readable (that is, machine language)


code that can be run directly by the given computer system. The machine language code


contains sequences of primitive instructions for the given computer in binary


representation. On the other hand, HLLs employ mnemonics of more powerful


instructions, and appropriate structures to make programming easy and independent of


the target computer.


From the software point of view, a computer is a six- level system consisting of the digital


logic (collections of electronic gates), microarchitecture (a collection of functional units,


such as ALUs - Arithmetic Logic Units, and their interconnectivity), instruction set


architecture (the complete set of machine language instructions), operating system (code


that monitors and controls the activities of the computer), assembly and machine


language, and high-level language. The assembly language is very close to the machine


language of a computer; it basically replaces the binary representation of machine


instructions with mnemonics in a one-to-one fashion. From the hardware point of view, a


computer is conveniently assumed to be a five- level hierarchy. The five levels correspond


to network ports for connecting to the outside world (these ports may not be necessarily


available, as a computer may be a standalone information processing and/or computing


machine), peripheral or mass-storage devices for (applications and system) program and


data storage, main memory, program and data caches (fast memories for retrieving data


by content), and CPU (Central Processing Unit) or processor. Specia l emphasis is given


in this article to the description of computer systems based on this five-level


representation. Many other components are also included in computer systems in order to


enable the aforementioned basic components to function properly. For example, control


and data busses are used to transmit data between any two successive levels of the


hardware hierarchy and glue logic is used to implement the appropriate interfaces. The


design of a computer system most often begins with the selection of a particular CPU.


The other components are selected progressively based on performance requirements.


Analytical techniques, software simulations, and software or hardware prototyping of the


complete or partial computer system are used to make final decisio ns about the design.


Special attention is given nowadays to hardware-software codesign, where the selection


or design of components is made in unison with the development of the corresponding


system software.


There exist several types of general purpose computer systems. These types are grouped


together into two major computer classes, comprising sequential or conventional


computers, and parallel computers, respectively. The class of sequential or conventional


computer systems comprises:



· Supercomputers.

The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy, and petroleum exploration.






The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.









· PCs (personal computers) or desktops.

These computers also are of the


microcomputer type. Figure 1 shows the basic components of a microcomputer. The


RAM and ROM form the main memory that stores system and application programs, and


data. The ROM contains only part of the operating system, and most often the part that


initializes the computer. The sofware stored in the ROM is called firmware. Resource


interface units form the required glue logic for the implementation of the required data


exchange protocols. The control bus transfers the control signals produced by the


microprocessor. To access an element in the memory or a peripheral device, the


microprocessor first issues the address of that item on the address bus. The address bus is


unidirectional, from the processor to the other units. While the latter value is still present


on the address bus, the microprocessor issues the appropriate control signals to read or


write from the corresponding location. The address issued by the microprocessor is


decoded by external logic to choose the appropriate memory module or I/O device. The


data is finally transferred on the bidirectional data bus. Details on how microcomputers


execute programs are presented in Section 2.







· 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.







Historically, workstations had offered higher performance than personal computers, especially with respect to CPU and graphics, memory capacity and multitasking capability. They are optimized for the visualization and manipulation of different types of complex data such as 3D mechanical design, engineering simulation (e.g. computational fluid dynamics), animation and rendering of images, and mathematical plots. Consoles consist of a high resolution display, a keyboard and a mouse at a minimum, but also offer multiple displays, graphics tablets, 3D mice (devices for manipulating and navigating 3D objects and scenes), etc. Workstations are the first segment of the computer market to present advanced accessories and collaboration tools.






Presently, the workstation market is highly commoditized and is dominated by large PC vendors, such as Dell and HP, selling Microsoft Windows/Linux running on Intel Xeon/AMD Opteron. Alternative UNIX based platforms are provided by Apple Inc., Sun Microsystems, and SGI.





· Minicomputers.

High-performance cabinet-sized computers that can be used


simultaneously by a few dozens of users. They are often used in engineering and


scientific ap
They appeared in the 1980s as single-user computers with much


better performance than PCs, primarily because they contain very advanced


microprocessors. They often include proprietary co-processors to facilitate graphics


functions because they basically target the scientific and engineering communities. They


were uniprocessor computers in the early days, but multiprocessor workstations appeared


for the first time in the market a few years ago. They are now often used as multi-user


platforms.
plications. They have been replaced recently by advanced workstations and


networks of workstations.







· Mainframes.

Very powerful computers that can serve many dozens or hundreds


of users simultaneously. IBM has produced numerous computers of this type. They have


been replaced recently in many occasions by networks of workstations.






Describe a typical use for mainframe computers






Mainframes are computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry/consumer statistics, ERP, and financial transaction processing.






The term originated during the early years of computing and referred to the large mechanical assembly that held the central processor and input/output complex. Later the term was used to distinguish high-end commercial machines from less powerful units which were often contained in smaller packages. Today, this term almost exclusively refers to IBM System z9 mainframes, the lineal descendants of the System/360.






Differentiate Workstation from personal computers






A work station may not, necessarily, have all of the components located in one physical space.


As part of a network the work station may connect to a server to access databases, printers, etc.


A PC is usually a self contained system, that includes all components and peripherals






Identify types of personal computer














Workstation


Sun SPARCstation 1+, 25 MHz RISC processor from early 1990s


Main article: Workstation


A workstation is a high-end personal computer 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. Workstations are used for tasks such as computer-aided design, drafting and modelling, computation-intensive scientific and engineering calculations, image processing, architectural modelling, and computer graphics for animation and motion picture visual effects.


















Desktop computer


Dell OptiPlex desktop computer


Prior to the wide spread of PCs a computer that could fit on a desk was considered remarkably small. Today the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small form factor models that can be tucked behind an LCD monitor. In this sense, the term 'desktop' refers specifically to a horizontally-oriented case, usually intended to have the display screen placed on top to save space on the desk top. Most modern desktop computers have separate screens and keyboards.






















Single unit


Single unit PCs (also known as all-in-one PCs) are a subtype of desktop computers, which combine the monitor and case of the computer within a single unit. The monitor often utilizes a touchscreen as an optional method of user input, however detached keyboards and mice are normally still included. The inner components of the PC are often located directly behind the monitor, and many are built similarly to laptops.






A mid-range HP Laptop.


A laptop computer or simply laptop, also called a notebook computer or sometimes a notebook, is a small personal computer designed for portability. Usually all of the interface hardware needed to operate the laptop, such as USB ports (previously parallel and serial ports), graphics card, sound channel, etc., are built in to a single unit. Laptops contain high capacity batteries that can power the device for extensive periods of time, enhancing portability. Once the battery charge is depleted, it will have to be recharged through a power outlet. In the interest of saving power, weight and space, they usually share RAM with the video channel, slowing their performance compared to an equivalent desktop machine.


One main drawback of the laptop is sometimes, due to the size and configuration of components, relatively little can be done to upgrade the overall computer from its original design. Internal upgrades are either not manufacturer recommended, can damage the laptop if done with poor care or knowledge, or in some cases impossible, making the desktop PC more modular. Some internal upgrades, such as memory and hard disks upgrades are often easy, a display or keyboard upgrade is usually impossible. The laptop has the same access as the desktop to the wide variety of devices, such as external displays, mice, cameras, storage devices and keyboards, which may be attached externally through USB ports and other less common ports such as external video.


A subtype of notebooks, called subnotebooks, are computers with most of the features of a standard laptop computer but smaller. They are larger than hand-held computers, and usually run full versions of desktop/laptop operating systems. Ultra-Mobile PCs (UMPC) are usually considered subnotebooks, or more specifically, subnotebook Tablet PCs (see below). Netbooks are sometimes considered in this category, though they are sometimes separated in a category of their own (see below).


Desktop replacements, meanwhile, are large laptops meant to replace a desktop computer while keeping the mobility of a laptop. Entertainment laptops emphasize large, HDTV-resolution screens and video processing capabilities.










Pocket PC


An O2 pocket PC


A pocket PC is a hardware specification for a handheld-sized computer (personal digital assistant) that runs the Microsoft Windows Mobile operating system. It may have the capability to run an alternative operating system like NetBSD or Linux. It has many of the capabilities of modern desktop PCs.


Currently there are tens of thousands of applications for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices also include mobile phone features. Microsoft compliant Pocket PCs can also be used with many other add-ons like GPS receivers, barcode readers, RFID readers, and cameras. In 2007, with the release of Windows Mobile 6, Microsoft dropped the name