Количество символов в тексте: 3727
Четырнадцатый текст
Programming
Programmers use a logical series of procedures to write a program. The main steps involved in programming are:
First, the programmer has to analyze the problem and define the purpose of the program. The task must be restated as a precise list of events leading to a solution.
Secondly, he has to design an algorithm, which is a step-by-step plan that describes these events in a simple logical sequence. This plan usually takes the form of a flowchart which is a diagram that uses standardized symbols showing the logical relationship between the various parts of the program. These special symbols show how the computer works through the program - where it makes decisions^ where it starts and ends, and things like that.
Later these logical steps are translated into instructions written in the computer language used for that program. This is called "coding". The program is then "complied", which means that the high- level code is translated into binary code, the only language that computers understand. The function of compilers is to convert a source program into an object program. Compilers convert a program written in a high-level language into a program written in a lower level language. Special test programs can be run to detect errors or 'bugs' in the program. This process is called "debugging". The programmer must trace each error back to its origin, then write the correct instruction, recompile the program and conduct another series of test runs. Debugging continues until the program runs smoothly. Finally, the programmer writes documentation for the user. Manuals provide instructions on how to use the program.
With a database you can store, organize and retrieve a large collection of related information on computer. Information is entered on a database via fields. Each field holds a separate piece of
information and the fields are collected together into records. Records are grouped together into files which hold large amounts of information. Files can easily be updated: you can always change fields, add new records or delete old ones. With the right database software, you're able to keep track of all the details that can make you successful Another feature of database programs is that you can automatically look up and find records containing particular information. If we had to summarize the most relevant advantages of a database program over a card index system (a catalogue), we would say that the former is much faster to consult and update, occupies a lot less space and records can be automatically stored into numerical or alphabetical order using any field. The best packages also include networking facilities, which add a new dimension of productivity to business. Thanks to security devices, you can share part of your files on a network and control who sees the information. Most aspects of the program can be protected by user-defined passwords. Such features like mail merging, layout design and the ability to import and export data are also very useful.
Количество символов в тексте: 2533
Пятнадцатый текст
Basic Uses of the Internet
I. The information superhighway, or the Internet, is the world's largest computer network. It is a network made up of thousands of smaller networks. The purpose of the Internet is to exchange information and improve communication.
The concept of the superhighway communication system started back in the 1960s when the threat of cold war was looming and the United States government worried about how people would communicate in the event of war.
In 1969 The United States formed ARPANET to link defense contractors and universities doing defense research together using computers. This permitted instant communication, but the system soon grew too big for the military to handle on their own. More academic institutions became involved, and the network expanded to include academic and research facilities around the world. There are now millions of users and hundreds of thousands of host computer networks in over 135 countries around the world.
The Internet can be used in many ways, but the three most common functions are electronic mail or e-mail, gopher and File Transfer Protocol or FTP.
To join the Internet you need some kind of computer, but which is more or less irrelevant. So, you might be using a powerful Unix-based workstation, a PC running Microsoft Windows, an Apple Macintosh, or an Atari: all of these can be used without problem since the Internet was built specifically to interconnect the most disparate kinds of computers. Nor does the speed of the computer matter that much: the Internet is about communications, and involves using the power of other computers located elsewhere. Your own will be largely engaged in sending instructions to other, probably more powerful, machines (this is usually known as the client-server model, where the computer you use is the client which sends requests to a server, in this case generally located elsewhere on the Internet).
There are good reasons for choosing a reasonably powerful machine. First, it will let you run all the most up-to-date software: it is largely through a new generation of easy-to - use Windows software that the Internet has suddenly become accessible to everyone. Some of these new programs are quite large and make greater demands on the PC than older software. For example, the Windows 95 operating system comes with many Internet elements already built-in, but requires more hardware power than earlier versions of Windows. Similarly, the bigger your hard disk is, the more you will be able to explore the Internet. The reason for this is simply that you will find so much to download that disk space may prove to be a constraining factor on your explorations. In any case, hard disk costs have fallen so dramatically in recent years that even a disk with a capacity of many hundreds of Mbytes is now reasonably priced. To use your personal computer on the Internet, you need some way of connecting it. By far the commonest method of effecting a link between you and the global online community is to use the telephone.
Typically you will use a modem to connect your computer to the dial-up line (there are other options like ISDN - Integrated Services Digital Network - but the principles remain the same.) Whereas the power of your personal computer does not affect too much the speed at which you can access the Internet, your choice of modem does, critically. For this reason, if you intend using the Internet for anything more than the simplest e-mail you are strongly advised to buy a fast modem. Fast in this context means one that has a basic throughput of 14400 bits per second. In fact, with аду kind of normal use a faster modem will pay for itself in a few months: the greater throughput means that you will spend much less time on the phone downloading files, and the resulting savings on the phone bill will quickly cover any extra cost for the modem. From The Internet with Windows1, 1996