Detailed System Design

Detailed System Design

As we already know the concept is a sketch of the structure and/or skeleton of the Information System, it guides the detailed design hence adding flesh to make it move towards becoming the system. As the scope and general configuration of the Information System have been established, the detailed design of the system may be started.

Sometimes it is impractical to explain each and every steps of doing procedure for detailed design for the following reasons.

1. There is a wide variety of approaches to system design in terms of organizing, conducting and defining it.
2. Systems design is a complex of concurrent activities where as the nature of description can proceed along only one line.

The first step in systems design is not a technical one. It is concerned with gaining support for the work that follows. Systems designers must have the support of most members of the organization to obtain information for the design of the system and to obtain acceptance of the final system.

Therefore, at least members of the organization should be informed of the objectives and nature of the study. It is preferable to draw many members into the study.

Aim of the detailed design

The detailed design of an Information System is closely related to the design of operating systems.

The aim of the detailed design is to furnish a description of a system that achieves the goal of the conceptual system design requirements.

This description consists of drawings, flowcharts, equipment and personnel specifications, procedures, support tasks, specification of information files, and organization and operating manuals required to run the system.

Conceptual design gives the overall performance specifications for the Information System; the detailed design yields the construction and operating specifications.




Document the detailed design

The end of the detailed design project is production of the documents that specify the system, its operation, and its design justification.

Documentation Consists of
1. A summary
2. Detailed flowchart
3. Operations activity sheets showing inputs, outputs and transfer functions.
4. Specification of the data base or master file.
5. Computer hardware requirements.
6. Software (programs)
7. Personnel requirements by type of skill or discipline.
8. Final (updated) performance specifications.
9. Cost of installation and implementation of the system.
10. Cost of operating the system per unit of time.
11. Program for modification or termination of the system.

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Implementation, Evaluation and Maintenance of Information System

Implementation, Evaluation and Maintenance of Information System

Implementation

The design of a management information system may seem to management to be an expensive project, the cost of getting the MIS on line satisfactorily may often be comparable to that of its design, and the implementation has been accomplished when the outputs of the MIS are continuously utilized by decision makers.

Once the design has been completed, there are four basic methods for implementing the MIS.
These ares-
1. Install the system in a new operation or organization.
2. Cut off the old system and install the new
This produces a time gap during which no system is in operation. Practically, installation requires one or two days for small companies or small systems.
3. Cut over by segments
This method is also referred as” phasing in” the new system. Small parts or subsystems are substituted for the old. In the case of upgrading old systems, this may be a very desirable method.
4. Operate in parallel and cut over.
The new system is installed and operated in parallel with the current system until it has been checked out, then only the current system is cut out. This method is expensive because of personal and related costs. Its big advantages are that the system is fairly well debugged when it becomes the essential information system.

Plan the implementation

The three main phases in implementation take place in series.
These are

1. The initial installation
2. The test of the system as a whole
3. The evaluation, maintenance and control of the system.

Many implementation activities should be undertaken in parallel to reduce implementation time. Training of personnel and preparation of software may be in parallel with each other and with other implementation activities.

The first step in the implementation procedure is to plan the implementation. Some analyst includes the planning of the implementation with the design of the system, the planning and the action to implement the plan should be bound closely together. Planning is the first step of management, not the last. The MIS design and the urgent need for the system at the time the design is completed will weigh heavily on the plan for implementation.

Implementation Tasks

The major implementation tasks consists of-

1. Planning the implementation activities
2. Acquiring and laying out facilities and offices
3. Organizing the personnel for implementation
4. Developing procedures for installation and testing
5. Developing the training program for operating personnel.
6. Completing the system’s software
7. Acquiring required hardware
8. Generating files
9. Designing forms
10. Testing the entire system
11. Completing cutover to the new system
12. Documenting the system
13. Evaluating the MIS
14. Providing system maintenance(debugging and improving)


1. Planning the implementation activities

Establish Relationships among tasks

For small projects, the order of performance may simply be described in text form. A Gantt chart or network diagram makes visualization of the plan and schedule much clearer.

For large projects, many concurrent and sequential activities are interrelated so that a network diagram must be employed in any good plan.
Establish a Schedule

Schedule is prepared by having the system designers estimate the times between the events in the program network. The critical path (longest time through the network) can be calculated. After specifying the starting date, the end date is established.

Cost Schedule to Tasks and Time

The cost for completing each task required to complete is established as part of the plan; then the rate of expenditures should be budgeted.

Reporting and control of the work in progress may be obtained by weekly meetings. The financial personnel must make certain that report formats allow them to show cost and technical progress relationship as well as cost and time.

2. Acquiring and laying out facilities and offices

For the installation of a new system to replace a current one may require a major revision of facilities as well as completely new office, computer room etc.

The MIS project manager must prepare rough layouts and estimates of particular floor areas that feel to be needed. The manager then prepares cost estimates.

Space planning must be done by the space to be occupied by people, the space occupied by equipment and the movement of people and equipment in the work progress. A large investment in good working conditions will repay its cost many times.

3. Organizing the personnel for implementation

As the implementation tasks have been defined, management usually assigns a project manager to guide the implementation.

The purpose of the MIS is to increase the amount and quality of their contributions, the system is their system.

Top management must make the middle managers for their involvement in implementation, besides these, systems specialists, computer programmer; top management should make sure that each people who will operate the system should have active parts in the implementation.

4. Developing procedures for installation and testing
After organizing the personnel for implementation the next task is to develop or prepare the procedures for implementation. As the project leader has the network plan for proceeding with the implementation, this leader calls the key people in the project to prepare more detailed procedures for system installation.

Procedures for evaluating and selecting hardware must be spelled out. Procedures for phasing in parts of the MIS or operating the MIS in parallel must be developed.

The major part of implementing the MIS is the testing of each segment of total system as it is installed.

5. Developing the training program for operating personnel

A program is developed keeping in mind to impress management and support. After developing the program, it is necessary to train operating personnel in their new duties. They must have a thorough understanding of what the new MIS is like and what it is supposed to do. They must learn how it will operate. They are faced with many changes in their work and have to obtain acceptance of changes.

As there are various levels of personnel and these people will be working with only a small part of the MIS, the seminars should be designed to provide them with an understanding of the complete system.

6. Completing the system’s software

As the software is developed internally or under contract, in both cases, the software development must take in mind the nature of the hardware required.
As the system designers and programmers provide the flow diagrams and the block diagrams during the detailed design state. Some modification may be required, as the implementation stage progresses.

7. Acquiring required hardware

This acquisition is usually the limiting factor in getting am MIS implementation. These tasks should be started during the design stage.

The decision is to be needed, whether to buy or lease the hardware. Capital expenditure analysis is only one of many factors involved in this decision. Others are prestige, usage etc.

8. Generating files

In the implementation stage, the actual data must be obtained and recorded for the initial testing and operation of the system. This requires format of the data, storage form and format and remarks to indicate when the data have been stored.

The collection of data used in routine operations is often called the master file.

Responsibility for file maintenance for each file item should also be assigned. The development of files or databases belongs to information system designers and storage and retrieval experts.

The translation of specifications for files into computer programs is a function of computer specialists.

9. Designing forms

For controlling the marketing, a salesperson has to fill out the forms summarizing the day’s activities. The form ensures the right information to be supplied for computer storage.

Forms are required not just for input and output but also for transmitting data at intermediate stages.

10. Testing the entire system

As the total system is installed, tests should be performed with the test specifications and procedure. A test during installation stage consists of component tests, subsystem tests and total system acceptance tests.

Components may be equipment (that can be new or old), new software programs, new data collection methods, work procedures, reporting formats. Difficulties that occur during component tests may lead t design changes.

As more components are installed, subsystems may be tested. There is a difference between the testing of component and the testing of a system.

System tests require verification of multiple inputs, complex logic systems, and timing aspects of many parts.

11. completing cutover to the new system

Cutover is a point at which the new component replaces the old component to the new system replaces the old system. This involves old forms, old files and old equipment being retried.
The debugging proves associated with the cutover to the new system may extend for several months.

12. Documenting the system

Documentation of the MIS means preparation of written descriptions of the scope, purpose, information flow components, and operating procedures of the system.

Documentation is a necessity for troubleshooting, for replacement of subsystems, for interfacing with other systems, for training new operating personnel and also for evaluating and upgrading the system.

13. Evaluating the system

After the MIS has been operating smoothly for a short period of time, an evaluation of each step in the design and of the final system performance should be made.

Evaluation should not be delayed beyond the time when the system’s analysts have completed most of the debugging. The longer the delay, the more difficult it will be for designer to remember important details.

The evaluation should be made by the customer as well as by the designers.

14. Providing system maintenance

Control and maintenance of the system are the responsibilities of the line managers.

Control of the systems means the operation of the system as it was designed to operate. Sometimes, well-intentioned people or operators may make unauthorized changes to improve the system, changes that are not approved or documented.

Maintenance is closely related to control. Maintenance is that ongoing activity that keeps the MIS at the highest levels of effectiveness and efficiency within cost constraints.

Maintenance is directed towards reducing errors due to design, reducing errors due to environmental changes and improving the system’s scope and services.

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Conceptual System Design

Conceptual System Design

During the system analysis, the analysis of system data is very important. Analysis of data is made up of more than one level at the beginning (first level) and different ideas are used at each level. At first level, analyst develops a conceptual system design.

Since the conceptual design sets the direction for the management information system (MIS). It is vital that managers participate seriously and heavily at this stage. Conceptual design is sometimes called feasibility design, gross design or high level design.

The conceptual design phase takes as input.
1. A crisp statement of a management information requirement and
2. a set of management objectives for the MIS

In the conceptual design stage that the alternative overall MIS designs are conceived and the best one is selected by the system analyst in consultation with the top management. The feasibility of meeting the management objectives for the MIS is assessed showing how the system will work at the high level is drawn. Therefore, conceptual design is also known as gross design; high level becomes the basis for the detailed MIS design.

Hence, conceptual design is a pre-design for the detailed design. In fact, conceptual design is the “centerpiece” of the process. Only after conceptual design is completed, it can be sure that the MIS can successfully be constructed.

The conceptual design involves the following tasks.

1. Defining problems in more details.
2. Refining the management objectives to set system objectives.
3. Establishing system constraints.
4. Determining information needs and their sources.
5. Developing alternative designs and selection one from these various designs.
6. Document the conceptual design and preparing the report.

1. Define the problem-

There is no doubt that problems exists in any dynamic business. The most important is that what are usually lacking are clear definitions of the problems and the priority system on the basis of problem is the main solution. Therefore, management must take the first step in MIS design by formulating problems to be solved. The problem can be solved by the iterative process.

The goal for the business leads to the objectives of the general business. From the objectives, plans are derived. Each business objectives and business plans are derived. Each business objectives and business plans are associated with information needs. These Information needs are the problems to be solved by the MIS function. The statements of needs are enough for designing process.
1. Stating the information need.
2. Asking questions about that need.
3. Suggesting interpretation of that need.
4. Detailing the original statement.
5. Reviewing the more detailed statement of need with management.
These steps are repeated until the information needs and the problem to be solved are really understood. The process of problem refinement flows naturally into the system objectives.



2. Set System Objectives

Most of the time it is quite difficult to state objectives for systems that covers all the functional areas.
The manager must define the system objectives in terms of the importance of information demands and not in terms of the satisfaction of demands that are not related to an objective. System analyst tends to stress processing efficiency and staff and functional supervisors commonly believe that their objective is “to complete the required report in time for management use”. This view disregards the real objectives of the system design, management’s effectiveness.

The value of system lies in the benefits of the users. When we ask for the objectives, a college principal may reply,” provide quality education” and a government bureaucrat may say” provide more jobs for the unemployed”. Despite its difficulty being specific is necessary. System objectives should be expressed in terms of what managers can do after their information requirements have been met.
In summary, the first steps in systems design attempts to answer the question” what is the purpose of the system?” why it is needed? What is it expected to do? Who are the users what are their objectives?

3. Establish System Constraints

The iterative nature of the systems design process is easily understood when we consider the third step in the process-establishing constraints. It can also be called as problem boundaries or restrictions, constraints enable the designer to stipulate the conditions under which objectives may be attained and to consider the limitations that restricts the design. The two steps of setting objectives and establishing constraints may be considered together as one.
Constraints may be viewed as a negative limitation on systems design, there is a positive benefit also. Establishing constraints will help to ensure that the design is realistic.
Constraints may be classified as external or internal to the organization.

External Constraints
The external environment of the organization is concerned by the customer. Order entry, billing and other systems that interface with the customer’s needs in mind. If some outputs from the system are not acceptable to the customer, a definite limitation must be faced up.
The government imposes certain restrictions on the processing of data. That may be the need to maintain the security of certain classes of information to comply with law and regulation in the conduct of business (e.g. taxes, reporting).
Unions can also affect the operations of systems involving members in working conditions.
Suppliers are also an important group to be considered when designing information systems because these systems frequently interface with that group.

Internal Constraints
If top management support is not obtained for the systems concept and for the notion that computer based information systems are vital for management planning and control, the type of design effort cannot be implemented. A good environment for information systems must be set, and one essential requirement is the approval and support of the top management.

Organizational and policy considerations frequently set limit on objectives and modify an intended approach to design of the system. Company policies frequently define or limit the approach to systems designs.

Personnel needs and personnel availability are a major limiting factor in both the design and utilization of information systems. Computer and systems skills are among the most critical in the nation. The most significant constraint of all is the one concerning the people.

Cost is a major resource limitation. The cost to archive the objectives should be compared with the benefits to be derived.

Self-imposed restrictions are these placed on the design by the manager or the designer. The manager will also restrict the amount of time and effort devoted to investigation. To achieve the objective, the manager may have to scale down several requirements to make the system fit with other outputs, equipments or constraints.

4. Determining Information needs and sources

For a good system design, a clear statement of information needs is very important and necessary. Many organizations spend huge amounts on hardware and software to maintain existing systems or build sophisticated data banks, without first determining the real information needs of management: the information that can increase the ability of managers in critical areas such as problems, alternatives, opportunities and plans.
The optimum results cannot be achieved unless managers can provide the specifications for what they want out of an information system. The manager needs information for variety of reasons concerned with the management process. The type of needs at various times and various purposes depends largely upon two factors.
a) The personal managerial attributes of the individual manager and
b) The organizational environment in which decisions are made.
The information sources are important for determining information needs. The system may require external information or the internal.

5. Alternative conceptual designs and selecting one

The development of a concept of a system is a creative process that involves synthesizing knowledge into some particular pattern. The concept of an MIS would consist of the major decision points, patterns of information flow, channels of information and roles of managers and competitors. The concept is the sketch of the structures or skeleton of the Information System, which guides and restricts the form of the detailed design. If conceptual design is the skeleton, then detailed design is the flesh.

E.g. two teams of students are trying to do project on the tourist guide and contact information system. One concept produced is a sketch showing a detail about the particular places describing its culture, heritages along with the colleges. Hotels and trade. Where as another team produces a sketch of description of colleges along with the description of faculty and the fee structures on various needs.

It is obvious that each alternative concept of a system has advantages and disadvantages. Sometimes one concept will dominate all others by major criteria.

6. Document the best design

Sufficient information has been accumulated to begin a more detailed description of the system concept. This description includes essentially a flowchart or other documentation of the flow of information through the system, the inputs and the outputs.

The manager should be involved to the extent that the system provides the information required, the designer is concerned with the nature of the materials and equipment as well as with technical processing considerations.

Details to be worked out later by the designer will include exact instructions as what data are to be captured and when, the files are to be used, the details of how processing is to be done, what outputs will be generated by the system etc.

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Definition, Bus, Ring, Star Topology

The computers on LAN can be physically connected with the wires in different manner as the requirement of an organization or office. The manner in which the computers on the LAN are connected is known as LAN Topology. So, network topology is the physical layout of cabling for connecting computers on the network. It can be defined as the arrangement or connection pattern of computers on a LAN. A LAN topology describes how the computers are physically connected and how do they communicate on the network. It determines the data paths that may be used between any pair of nodes of the network. There are three basic network topologies. They are Bus topology, Ring topology and Star topology.

BUS TOPOLOGY

In a bus topology computers are arranged in the linear format. So, it is called Linear Topology. In this topology, all nodes are connected directly to the common cable with the help of T-connectors. The common cable is also known as also known as a network bus or trunk. The network bus acts as a backbone to the network.Many different lengths of co-axial cables are used in this type of topology. On the both side of the network bus (i.e. coaxial cable), BNC (Bayonet Naur Connector) jacks are connected. A T-connector is used to join segments of cables and computers. The BNC jack on each side of network bus is connected to the T-connector i.e. top the T-connector is connected to the NIC card of a Computer. The T-connectors connected to the last computers on both sides are attached with terminators.

In this network topology, the position of the server is not fixed i.e. can be any where on the network. When any node sends the data, the data passes on both directions in the form of packets through the bus and reaches to all the nodes. Since each data packet contains the data bits and the destination address, only the destination node accepts the data packets. The terminators at both end sides absorb the packets or signals travelling on the bus to prevent the bouncing of the signals which causes interference.

ADVANTAGES

a. Since each small segments of cables are joined to form a trunk or network bus it is easy to setup computers on the bus.

b. Since nodes are arranged in the linear form, it requires the less amounts of cables.

c. The coaxial cables used for networking are inexpensive and joining connectors on the cables is also easy.

d. Failure of any node does not affect other nodes on the topology.

e. Well suited for temporary networks (quick set

up).

DISADVANTAGES

a. If the backbone cable i.e. network bus has problem then the entire network fails.

b. Finding fault on this topology is not easy.

c. It provides limited flexibility for change, so adding or removing nodes in between is not easy.

d. The performance degrades when the

number of computers is more on the. so, it is not suitable for big size network.

RING TOPOLOGY

In a ring topology, all nodes are arranged in the shape of a circle (ring). Both ends of a cable are connected to the nodes so there is no any point like a bus topology. Since the both ends are connected to the nodes there is no any terminator in this topology. In this topology, many different lengths of co-axial cables are used according to distance of computers. In this topology each computer acts like a repeater that boosts an incoming signal before passing it on to the next computer.

In this topology, data or messages are transmitted in one direction either clockwise or anticlockwise. When any node sends a message or data, the message or data reaches to the first node on the circle. If the first node in the circle is the destination node then it absorbs the data or message otherwise it regenerates the signal and passes to another node on the loop and so on. If the message or data is not absorbed by any node then it is absorbed by the sender node.

ADVANTAGES

a. Since each node on the ring acts as a repeater, no any external repeater is required to boost up the signals.

b. It supports high data transmission. Rate.

c. It is easy to setup.

DISADVANTAGES

a. If any node or connecting cable fails the entire network does not work.

b. The diagnosis of the fault is difficult.

c. Since data or message reaches on the node in sequence, so addition of few nodes increases the communication delays.

d. It provides limited flexibility for change,

so adding or removing nodes in between is not easy.

STAR TOPOLOGY

Star Topology is the most popular topology used to connect computers and other network devices on the network. In a star topology all nodes are connected through a centrally located device in the form of star. But the shape of arrangement of computers is not necessarily to be star. The device whic

h connects computers on the network is either a hub or a switch. A hub or a switch has connecting ports or slots where the wires running from each node are connected. A twisted pair cable (specially unshielded twisted pair cable) is used for connecting a computer and a hub or switch. Each segment of UTP cable is attached with RJ-45 jacks. And one side of the UTP cable is connected to the node and another side is connected to the hub or switch. When any node sends data or message, the data or message reaches to the hub or switch and then to the targeted computer on the network.

ADVANTAGES

a. Computers can be added or removed easily without affecting the network.

b. If any of the workstation or the connecting cable fails, it does not affect the remaining portion of the network.

c. Fault detection in the star topology is easy.

d. It is easy to extend so it is suitable for a large network.

e. It is one of the reliable network topology.

DISADVANTAGES

a. Since each node is required to connect with the centralized hub or switch more cables are needed which increases the cost of installation.

b. The entire network fails if there is any problem on the hub or switch.

c. In comparison to Linear and Ring topologies, it is little expensive as it requires more length of cables and other controlling devices.

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Definition of Computer Virus, Protection

Computer viruses are the software programs that have the ability to clone itself and can operate without the knowledge or desire of the computer user. In other words, a computer virus is a program designed to spread itself by first infecting executable files or the system areas of hard and floppy disks and then making copies of itself. Computer virus can transfer from different

means to a computer without the knowledge and permission of the user and they can hide themselves in other files. Whenever a host file or program is used, the virus become active and performs destructive tasks such as dislocating, deleting and changing contents of files. It infects data or program every time the user runs the infected program and it takes advantages and replicates itself. It is the intellectual destructive creation of computer programmer.

In 1949, Dr. John Von Neumann introduced the concept of replicate computer program. The first replicating program named “Creeper” was reported during 1970 in the network system of American department of Defense. In 1983, an American electronic engineer ‘Fred Cohen’ had used the word “Computer Virus” in his research paper for the program that replicates andprevents other programs to be executed. In 1987, two Pakistani brothers , Amjad and Basti released the first IBM virus “C-Brain” to stop illegal reproduction of software developed from Alvi’s Brain Computer Shop. An Indonesian programmer released the first antivirus software in 1988 to detect the C-Brain virus. This antivirus software could remove C-Brain from a computer and immunized the system against fur

ther Brain attacks. After this event, people started to have much interest in viruses and various viruses have started to be produced.

The number of computer viruses is increasing day by day. The nature of virus varies from each other. Virus spread from computer to computer through electronic bulletin boards, telecommunication systems, and shared floppy disks, pen drives, compact disks and the Internet. Viruses are created by computer programmers for fun, but once they began to spread they take on a life of their own. Antivirus software are developed to protect from computer virus.

PURPOSE OF CREATING COMPUTER VIRUS

1. To stop the software privacy. Software

can be easily copied from one computer to another computer. In order to stop software piracy, the programmers of the software themselves create computer viruses.

2. To entertain the users by displaying interesting messages or pictures.

3. To steal data and information.

4. To remind the incidents that happened at different time.

5. To destroy data, information and files.

6. To expose their programming ability.

7. Computer viruses are made in order to earn the money.

Computer viruses activate when the infected files or programs are used. Once a virus is active it may replicate by various means and tries to infect other files or the operating system. When you copy files or programs from a infected computer, the viruses also transfer along with files or programs to the portable disk which in turn transfers viruses to another computer whenever it is used. So, mostly the computers get infected through the external sources. The most common ways through which viruses spread are:

· Sharing of infected external portable disk like floppy disk, pen drive or compact disk.

· Using pirated software.

· Opening of virus infected e-mail messages and attached files.

· Downloading files or programs from the web

site, which are not secured.

· Exchanging of data, information or files over a network.

The number of viruses is increasing daily and each virus possesses different characteristics. It is very difficult to know whether a computer is infected with viruses or not. You may see the following symptoms, if a computer is infected with computer viruses.

· Programs take more time to load, fail to load or hang frequently.

· Unexpected messages or images appear su

ddenly on the screen.

· Displays unusual error messages or encounters errors frequently.

· Missing of files or appearing of unexpected files.

· Displaying low memory message frequently.

· Programs open automatically without giving instruction.

PROTECTION FROM VIRUS

We have already known that, viruses are harmful to our computers. They affect our computer systems. Virus can damage our important files and programs. They make our computer slow. Similarly, viruses create several effects to our computers and they irritate the users frequently. So, protection and prevention of our computer from viruses is necessary. If we follow some tips, we can prevent computer from viruses.

Some general tips on prevention and protection from virus infections are as follows:

1. Install anti-virus software from a well known, reputable company and use it regularly.

2. Update the Anti-virus software frequently in order to get the latest virus definition and scan the hard disk using latest virus definition because new viruses come out every single day.

3. Install an ‘on access’ scanner and configure it to start automatically each time you boot your computer system. This will protect your system by checking for viruses each time your computer accesses an executable file.

4. Virus scans any programs or other files that may contain executable code before you run or open them, no matter where they come from. There have been the cases of commercially distributed floppy disks, pen drives and CD-ROMs spreading virus infections.

5. If your E-mail or news software has ability to automatically execute Java Script, word macros or other executable, code contained in or attached to a message, it strongly recommended that you should disable this feature.

6. Be extremely careful about accepting programs or other files during on-line chat session. This seems to be one of the more common means that people wind up with virus or Trojan horse problem.

7. Do backup your entire system on a regular basis. Because some viruses may erase or corrupt files on your hard disk and recent backup data can be recovered.

8. Before using the pen drives of others, check it whether it is virus infected or not. First scan and then only open it.

9. Do not use pirated software.

10. Lock the computer system using password to prevent your computer from being used by others.

11. Do not download any programs from Internet unless you are confirmed they are virus free.

12. Be careful! While checking mail having attached documents.

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HISTORY OF CPU

EARLY COMPUTERS

In the first computers, CPUs were made of vacuum tubes and electric relays rather than microscopic transistors on computer chips. These early computers were immense and needed a great deal of power compared to today’s microprocessor-driven computers. The first general purpose electronic computer, the ENIAC (Electronic Numerical Integrator And Computer), was introduced in 1946 and filled a large room. About 18,000 vacuum tubes were used to build ENIAC’s CPU and input/output circuits. Between 1946 and 1956 all computers had bulky CPUs that consumed massive amounts of energy and needed continual maintenance, because the vacuum tubes burned out frequently and had to be replaced.

TRANSISTOR

A solution to the problems posed by vacuum tubes came in 1948, when American physicists John Bardeen, Walter Brattain, and William Shockley first demonstrated a revolutionary new electronic switching and amplifying device called the transistor. The transistor had the potential to work faster and more reliably and to consume much less power than a vacuum tube. Despite the overwhelming advantages transistors offered over vacuum tubes, it took nine years before they were used in a commercial computer. The first commercially available computer to use transistors in its circuitry was the UNIVAC (UNIVersal Automatic Computer), delivered to the United States Air Force in 1956.

THE INTEGRATED CIRCUIT (IC)

Development of the computer chip started in 1958 when Jack Kilby of Texas Instruments demonstrated that it was possible to integrate the various components of a CPU onto a single piece of silicon. These computer chips were called integrated circuits (ICs) because they combined multiple electronic circuits on the same chip. Subsequent design and manufacturing advances allowed transistor densities on integrated circuits to increase tremendously. The first ICs had only tens of transistors per chip compared to the millions or even billions of transistors per chip available on today’s CPUs.

In 1967 Fairchild Semiconductor introduced a single integrated circuit that contained all the arithmetic logic functions for an eight-bit processor. (A bit is the smallest unit of information used in computers. Multiples of a bit are used to describe the largest-size piece of data that a CPU can manipulate at one time.) However, a fully working integrated circuit computer required additional circuits to provide register storage, data flow control, and memory and input/output paths. Intel Corporation accomplished this in 1971 when it introduced the Intel 4004 microprocessor. Although the 4004 could only manage four-bit arithmetic, it was powerful enough to become the core of many useful hand calculators at the time. In 1975 Micro Instrumentation Telemetry Systems introduced the Altair 8800, the first personal computer kit to feature an eight-bit microprocessor. Because microprocessors were so inexpensive and reliable, computing technology rapidly advanced to the point where individuals could afford to buy a small computer. The concept of the personal computer was made possible by the advent of the microprocessor CPU. In 1978 Intel introduced the first of its x86 CPUs, the 8086 16-bit microprocessor. Although 32-bit microprocessors are most common today, microprocessors are becoming increasingly sophisticated, with many 64-bit CPUs available. High-performance processors can run with internal clock rates that exceed 3 GHz, or 3 billion clock pulses per second.


CURRENT DEVELOPMENTS

The competitive nature of the computer industry and the use of faster, more cost-effective computing continue the drive toward faster CPUs. The minimum transistor size that can be manufactured using current technology is fast approaching the theoretical limit. In the standard technique for microprocessor design, ultraviolet (short wavelength) light is used to expose a light-sensitive covering on the silicon chip. Various methods are then used to etch the base material along the pattern created by the light. These etchings form the paths that electricity follows in the chip. The theoretical limit for transistor size using this type of manufacturing process is approximately equal to the wavelength of the light used to expose the light-sensitive covering. By using light of shorter wavelength, greater detail can be achieved and smaller transistors can be manufactured, resulting in faster, more powerful CPUs. Printing integrated circuits with X-rays, which have a much shorter wavelength than ultraviolet light, may provide further reductions in transistor size that will translate to improvements in CPU speed.

Many other avenues of research are being pursued in an attempt to make faster CPUs. New base materials for integrated circuits, such as composite layers of gallium arsenide and gallium aluminum arsenide, may contribute to faster chips. Alternatives to the standard transistor-based model of the CPU are also being considered. Experimental ideas in computing may radically change the design of computers and the concept of the CPU in the future. These ideas include quantum computing, in which single atoms hold bits of information; molecular computing, where certain types of problems may be solved using recombinant DNA techniques; and neural networks, which are computer systems with the ability to learn.

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