Computer System

Each computer consist of a series of devices that together operate as an integrated unit or computer system.

Here are the types of functional units:

1. Central processing unit
2. Input unit
3. Output unit
4. Auxiliary or secondary storage unit

The processor is made up of the memory, arithmetic, logic and control units. A larger computer system will normally have one or more auxiliary units, where input and output data are stored.

Why Computers Sometimes Fail

Why Computers Sometimes Fail

Now a days we've seen a rapid expansion of computers that mostly all people used computers for creating businesses, governments and private schools but now a days public schools they already starting to know what is computer and how it works.

But sometimes computers fails to meet its objectives of increased speed, accuracy, and meaningful information.

There are some common errors:

1. Input Errors: when data is entered into a computer it must be relatively error-free it is to be processed correctively.
2. Errors in Instructing a Computer: Computers operate on data using a set of instructions prepared by a programmer which are used to read data, process it, and produce output. Some programs contains errors and they called it "bugs" that do not become evident until a specific set of circumstances arises.
3. The Communication Gap: One main reason why computerized procedures frequently fail to meet their required objectives is because computer professionals and the people who will actually utilized the information, called "users" do not understand each others needs or have not communicated successfully. Users do not really understand what computers can and can't do and some other professional did not understand how best computer is.
4. Improper Controls: The need of computers increase rapidly and need proper control and security measures, the need of such control and security is even greater but most organizations neglected this area.
5. Lack of Standards: Lack of standards results in problems when an organization obtains new equipment, hires new computer professionals and attempts to provide some consistent set of procedures.
6. Lack of Adequate Manufacturer Support:
   

COMPUTER LIMATATIONS

Although computers are powerful and even marvelous tools, they have limitations. Thus, they can't be used indiscriminately .

Major Limitations of Computers:

1. Dependence on Prepared Instructions. The computer performs only what is programmed to do and nothing else. It can do much more than just add, subtract, multiply, and divide. By using instructions, it can sort data, straighten data out and store it away for you. Instructions allow the computer to compare two numbers, to find out if one is larger than, smaller than, or equal to the other. All these can only be possible if the computer is given the correct instructions. It can never do things by itself.

2. Inability to Derive Meanings from Objects. A computer does not have feelings. It is unable to recognize and respond to living objects. Accordingly, the meanings of objects such as data or programs, it deals with mean nothing to the computer. Whatever meanings the computer deals with are only fed to it by the programmer.

3. Inability to Generate Information. The computer cannot generate information own its own. It is not able to think and perceive relevant aspects of a given situation and adopt means to fulfill a goal or course of action. A computer has the capacity to put information together from many sources, only if properly programmed, but never independently.

4. It Cannot Correct Wring Instructions. The computer will do exactly what you instruct it to do, regardless of what you mean. It cannot decipher the correct instructions from the wrong instructions. It does not have the ability to select and perform only the rights.

COMPUTER CAPABILITIES

Many have pictured computer systems as having human or superhuman traits. Such views tend to exaggerate certain computer capabilities. The computer has also been described to be dumb machine since it is dependent entirely on those who control it. Use the wrong or faulty program, or use the wrong or inaccurate data, and you will get the wrong answer. The computer cannot think for itself. What is can do is extend man's problem-solving capabilities by performing many arithmetic, logic, branching and input/output instructions with lightning speed. It is powerful tool for extending man's brain power. It may be rightly called an intelligence amplifier.

Computers can enlarge man's brainpower because of the following capabilities and properties which had lead to the human or superhuman images created about it.

1. Ability to Perform Certain Logic Operations. Computers are symbol manipulators. It can manipulate in logical ways letter, numbers, words, sentences, mathematical expressions and other symbols to which people have giving meaning. It is able to perform a simple comparison and then, depending on the result, follow one of two or more predetermined branches or courses of action. This simple ability to compare is an important computer capability because more sophisticated questions can be answered by using combinations of comparison decisions.

2. Ability to Provide New Time Dimensions. The computer works one step at a time; it adds and subtracts numbers; it multiples and divides numbers; and it can be programmed to perform other mathematical operations. What is significant is the speed with which the computer can perform them. The computer is so fast that is saves a tremendous amount of time.

3. Ability to Store and Retrieve Information. The computer stores in internal storage both facts and instructions. The ease with which instructions can be changed gives the computer great flexibility . The access time required for information to be recalled from internal storage and be available for use is measured in microseconds or more precise units. Few machines that are used by man have this stored program ability.

4. Ability to control error. It has been estimated that a person would make one error in every 500- 1000 operations with a desk calculator. A computer can performed hundreds of thousands of arithmetic operations every second and can run error less for hours and days at a time.

5. Ability to Check Itself. Computers have the ability to check its own work. By a method known as parity checking, computers check on data when they enter storage, when they are moved internally, and when they leave in the form of output. The parity check performed by the computer involves the examination of each character's code to determine whether bits have been added or lost by mistake

CLASSIFICATION OF COMPUTERS ACCORDING TO CAPACITY

The term "capacity" refers to the volume of work or the data processing capacity a computer can handle. Their performance is judged by the:

1. Amount of data that can be stored in memory
2. speed of internal operation of the computer
3. number and type of of peripheral devices
4. amount and type of software available for use with the computer

The capacity of early generation computers were determined by their physical size- the large the size, the greater the volume. In computer terms, size and speed of operation are at present proportionate to each other. Generally, though, recent, technology is tending to create smaller machines, making it possible to package equivalent speed and capacity in a smaller format.

Computer System Classification

1. MICROCOMPUTERS= The mass production of silicon chips since 1971 has made it possible to put a "brain"into all sorts of machines. One such machine is the microcomputer. This machines has takes fullest advantage of the use of large-scale integration on silicon chips. The microprocessors literally contain a computer on a chip that can pass through the eye of needle. Microcomputers memories are generally made of semiconductors fabricated on silicons chips. It is a digital computer system under the control of a stored program that uses a microprocessor, a programmable read-only memory (ROM), and a random-access memory (RAM), The ROM defines the instructions to be executed by the computer while RAM is the functional equivalent of computer memory.

2. MINICOMPUTERS= Technological advances in the 1960's enabled manufactures to respond to the growing demand for a similar stand-alone machine, the minicomputer, to handle task that large computers could not perform economically. Minicomputer system (or small mainframe computers) provide faster operating speeds and larger storage capacities than microcomputers systems. They can support a large number of high-speed input/output devices. Several desk drives can be used to provide online access to large data files as required for direct- access processing.

Operating system developed for minicomputer systems generally support both multiprogramming and virtual storage. This means that many programs can be run concurrently. This type of computer system is very flexible and can be expanded to meet the needs of users.

Minicomputers usually have from 8k to 256K memory storage locations, and a relatively established applications software. although the minicomputer is not as powerful as the medium or large-size computer, it is quite close.

3. MEDIUM-SIZE COMPUTERS= it provide faster operating speeds and larger storage capabilities than small computer systems. They can support a large number of high-speed input-output devices, and several disk drives can be used to provide online access processing. Also support both multiprogramming and virtual storage. This allows the running of a variety of programs concurrently.

Medium-size computer system are very flexible; they can be expanded to meet the needs of users. The possibility of increasing the data processing capability of a computer by adding devices, such additional memory, and other peripheral devices, is called expandability.

4. LARGE COMPUTERS=are the ultimate in system sophistication, flexibility, and speed. They usually contain full control systems with minimal operator intervention. Large computer systems range from single-processing configurations to nationwide computer based networks involving general large computers. Large computers have storage capacities from 512K to 819K, and these computers have internal operating speeds measured in terms of nanoseconds, as a compared to smaller computers where speed in terms of microseconds.

5. SUPERCOMPUTERS= The biggest and fastest machines today are the supercomputers that are used when billions or even trillions of calculations are needed. These machines are essential for applications ranging from nuclear weapon to accurate weather forecasting.

Supercomputers are machines that have capabilities far beyond even the traditional large scale systems. Their speed is in the 100-million-instructions-per-second range.

CLASSIFICATION BY TYPE OF DATA HANDLED

There are essentially two different types of computer processing. Each is made possible by a different kind of circuitry , and each is suitable for different purposes.

1. Analog Computers = The name analog comes from the word "analogous", meaning similar. Analog computers are used for scientific, engineering, and process control purposes. Because they deal with quantities that are continuously variable., they give only approximate results. This types of computer provides an analog or simulation of the object or system it represents. It is especially useful for solving problems that involve relationships between variable quantities in systems that change with time. The analog compute may express changing relationships in output in the form of graphs. It is able to create such pictures because it responds to changes in electrical voltages that match changes in variable quantities.

2. Digital Computers = Is a machine the specializes in counting. It operates by counting values that are discrete, or separate and distinct, unlike the continuous quantities that can be measured by the analog computer. Digital Computers are used for both business data processing and accuracy. The basic operation performed by a digital computer is addition. It can store the sums of addition problems as they accumulate, and can complete a single calculation in a fraction of a nanosecond. The digital computer is capable of storing data as long as needed, performing logical operations, editing input data, and printing out the results of its processing at hight speed.

3. Hybrid Computers= Although both analog and digital computers are extremely used in widely accepted in various industries, manufacturers have to attempted to designed a computer that combines the best features of both types. This special-purpose machine called a hybrid, computer, combines the measuring capabilities of the analog computer and the logical and control capabilities of the digital computer. It offers an efficient and economical method of working out special types of problems in science and various areas of engineering. Some Hybrid machines contain special equipment to convert analog voltages into digital voltages,and vice-versa.