2. Computer as a means of communication

There exist two fundamentally different types of computers: analog and digital ones. There exist also hybrid types of computers that combine some of the properties of both analog and digital computers. In analog computers problems are solved by considering continuously changing data (electric current, voltage, resistance, pressure). But in practical usage the term "computer" usually refers to digital computers.

A digital computer is a complex system of four fundamentally different elements. What are they? In order to be able to use computers for practice, it is necessary to have elementary knowledge of its construction. Thus, the four main parts of a computer are: a central processing unit, input devices, memory-storage devices, and output devices. These four parts are linked by a communication network, or bus. These physical parts and all their physical components are called hardware.

As for the problem of hardware development, specialists believe that radically new computer designs are absolutely necessary! Almost all of today's computers process information one element at a time. But the problem could be solved much more quickly by the use of a great number of processors simultaneously working on the given task. And there already exists one such design called Thinking Machine. By using several thousand microprocessors the Thinking Machine outperforms many of today's supercomputers.

Without a program a computer is nothing but potential. A computer's operating system is the software. Without a software a computer does not operate.

The hardware and the software systems of a computer work together. Software is often stored in a computer's memory. Most often programs exist independently of the computer. When a software is loaded into a computer it automatically programs the computer to perform a specific task. It may be word processing, managing accounts and others.

Programming of a computer is performed by specialists. Software is written by professionals known as computer programmers. Often programmers in large corporations work in teams, each programmer focusing on a specific problem of a total project.

It should be noted that the hardware developments are dependent on well-written and well-formed software. Software controls the hardware, uses it, and forms an interface between the computer and its user. Nowadays software is becoming more and more user-friendly and easy to use even by non-computer professional users. Some word-processing programs help to solve problems, some game programs are becoming more difficult opponents the more they are played. Thus the term "personal computer" is taking quite a new meaning.

3. Computer System Organization

Computer is a fast and accurate manipulating system. The term “system” is used in many ways. For computer users, a system is a group of parts that are integrated for the purposes of achieving some objective. The three following characteristics are key:

1. A group of parts. A system has more than one element.

2. Integrated parts. A logical relationship must exist between system parts.

3. A common purpose of achieving some objective. The system is designed to accomplish one or more goals. All system elements should be tied together and controlled so that the system goal is achieved.

Since a computer is a group of integrated parts that have common purpose of performing the operations called for in the program being executed, it qualifies as a system.

Computer system is the input, processor and output elements.

Computer systems use input devices – machines used for data entry purposes. Some machine devices allow direct human/machine communication, while others require data to be recorded on an input medium such as magnetizable material. Devices that read data recorded on a specially coated plastic flexible or floppy disks and magnetic tapes are often used. The keyboard of a workstation connected directly to a computer is an example of a direct input device. Devices connected directly to a computer are said to be online to it. The mouse, input pen, touch screen, and microphone are other online input devices.

Processor unit is the heart of any computer system, which consists of primary storage, arithmetic-logic, and control elements.

1. The primary storage section (also called main memory) section is used for four purposes. Three of these relate to the data being processed:

a. Data are fed into an input storage area where they are held until ready to be processed.

b. A working storage space that’s like a sheet of scratch paper is used to hold the data being processed and the intermediate results of such processing.

c. An output storage area holds the finished results of the processing operations until they can be released.

d. In addition to these data-related purposes, the primary storage section also contains a program storage area that holds the processing instructions.

The separate areas used for these general purposes are not fixed by built-in physical boundaries in the storage section. Rather, they can vary from one application to another. Thus, a specific physical space may store input data in one application, output results in another, and processing instructions in a third. The person writing the application instructions determines how the space will be used for each job.

2. The arithmetic-logic section. The arithmetic-logic and control sections together make up the central processing unit (CPU). All calculations are performed and all comparisons (decisions) are made in the arithmetic-logic section of the CPU. Once data are fed into primary storage from input devices, they are held and transferred as needed to the arithmetic logic section, where processing takes place. No processing occurs in primary storage. Intermediate results generated in arithmetic-logic unit are temporarily placed in a designated working storage area until needed at a later time. Data may thus move from primary storage to the arithmetic-logic unit and back again to storage many times before the processing is finished. Once completed, the final results are released to an input storage section and from there to an output device.

3. The Control section. By selecting, interpreting, and seeing to the execution of program instructions, the control section of the CPU maintains order and directs operations of the entire system. Although the control section doesn’t process data, it acts as a central nervous system for the data-manipulating components of the computer. At the beginning of processing: the first program instruction is selected and fed into the control section from the program storage area. There it is interpreted, and from there signals are sent to other components to execute the necessary action. Further program instructions are selected and executed, one after another, until the processing is completed.