Testing the computer program

There are two kinds of errors or bugs with which program­mers must deal. The first type is the coding error. Such errors are syntax errors that prevent the language processor from suc­cessfully translating the source program to object program code. The language processor identifies the nature and the location of the error on the source program listing, so these errors are relatively easy to find and correct. The second type of bug is the logic error. The computer program can be successfully translat­ed, but the program does not produce the desired results. These errors are generally much more difficult to find and to correct than are coding errors. Logic errors can be avoided through careful planning of the program logic, but it is the programmer's responsibility to test thoroughly all of the program's functions, in order to verify that the program performs according to spec­ifications.

There are many tools provided to the programmer to help in debugging the program logic. These tools are called debug packages or tracing routines. They assist the programmer in fol­lowing the logic by printing out calculation results and field values used in making logic decisions in the program. In a few cases it may be necessary to use a memory dump — a printout of the instructions and date held in the computer's memory — in order to find the cause of logic errors.

 

Tests.

Test 1.

1. The most common___________________ for planning the program logic are flowcharting and pseudocode.

a) technologies; b) technics; c) techniques.

2.____________________ was designed for dealing with the complicated mathematical calculations of scientists and engineers, a) COBOL; b) FORTRAN; c) PL/I.

3.___________________ is the foundation of any programming languages.

a) a set of rules; b) a group of numbers; c) a lot of in­structions.

4. I / О match the physical and electrical charac­teristics of input-output devices.

a) interchanges; b) interfaces; c) interpretations.

5. Letter-quality, dot-matrix and ink-jet printers are all … printers.

a) line; b) page; c) character.

6. The most common device used to transfer information from the user to the computer is the.

a) keyboard; b) printer; c) modem.

7. Input-output units link the computer to its external

a) requirement; b) development; c) environment.

8. I / О devices can be classified according to their speed, visual displays being … devices.

a) high-speed; b)medium-speed; c) low-speed.

 

Test 2.

Match terms with their definitions.

1. Computer

2. Input

3. Output

4. Software

5. Hardware

6. Storage

7. CPU

8. CU

9. ALU

10. Program

 

a) an electronic device accepting data processing results from the computer sys­tem;

b) the unit performing arithmetic operations called for in the instructions;

с) the unit coordinating all the activities of various components of the computer. It reads information, enterpretes instruc­tions, performs operations, etc.;

d) a set of programs designed to control the operation of a computer;

e) lists of instructions followed by the con­trol unit of the CPU;

f) an electronic device keying information into the computer;

g) the unit holding all data to be processed, intermediate and final results of process­ing;

h) visible units, physical components of a data processing system;

i) the unit that directs the sequence of sys­tem operations, selects instructions and interpretes them;

j) a device with a complex network of elec­tronic circuits that can process informa­tion, make decisions, and replace people in routine tasks.

 

 

 

 

Unit XII.

The World Wide Web and the Internet.

Text 1.

The World Wide Web.

 

The WORLD-WIDE WEB

People have dreamt of a universal information database since late nineteen forties. In this database, not only would the data be accessible to people around the world, but it would also eas­ily link to other pieces of information, so that only the most important data would be quickly found by a user. Only recently the new technologies have made such systems possible. The most popular system currently in use is the World-Wide Web (WWW) which began in March 1989. The Web is an Internet-based computer network that allows users on one computer to access information stored on another through the world-wide network.

As the popularity of the Internet increases, people become more aware of its colossal potential. The World-Wide Web is a product of the continuous search for innovative ways of sharing information resources. The WWW project is based on the prin­ciple of universal readership; "if information is available, then any person' should be able to access it from anywhere in the world." The Web's implementation follows a standard client-server model. In this model, a user relies on a program (the cli­ent) to connect to a remote machine (the server), where the data is stored. The architecture of the WWW is the one of clients, such as Netscape, Mosaic, or Lynx, "which know how to present data but not what its origin is, and servers, which know how to extract data", but are ignorant of how it will be presented to the user.

One of the main features of the WWW documents is their hypertext structure. On a graphic terminal, for instance, a par­ticular reference can be represented by underlined text, or an icon. "The user clicks on it with the mouse, and the referenced document appears." This method makes copying of informa­tion unnecessary: data needs only to be stored once, and all ref­erenced to it can be linked to the original document.

SUCCESS of the WWW

Set off in 1989, the WWW quickly gained great popularity among Internet users. What is the reason for the immense suc­cess of the World-Wide Web? Perhaps, it can be explained by CERN's* attitude towards the development of the project.. As soon as the basic outline of the WWW was complete, CERN made the source code for its software publicly available. CERN has been encouraging collaboration by academic and commer­cial parties since the onset of the project, and by doing so it got millions of people involved in the growth of the Web.

The system requirements for running a WWW server are minimal, so even administrators with limited funds had a chance to become information providers. Because of the intuitive na­ture of hypertext, many inexperienced computer users were able to connect to the network. Furthermore, the simplicity of the Hyper Text Markup Language, used for creating interactive documents, allowed these users to contribute to the expanding database of documents on the Web. Also, the nature of the World-Wide Web provided a way to interconnect computers running different operating systems, and display information created in a variety of existing media formats.

In short, the possibilities for hypertext in the world-wide en­vironment are endless. With the computer industry growing at today's pace, no one knows what awaits us in the 21st century.

 

Text 2.