Part 2 Programming languages

Word list:

Read the text and say how many high level computer languages are mentioned in it.

Unfortunately for us, computer can’t understand spoken English or any other natural language. The only language a PC can directly execute is machine code, which consists of 1s and 0s (binary code).

This language is too difficult to write, so for this reason, we use symbolic languages to communicate instructions to the computer. For example, assembly language uses abbreviations such as ADD, SUB, MPY to represent instructions. The program is then translated into machine code by software called an assembler. Machine codeand assembly languageare called low-level languages because they are closer to the hardware. They are quite complex and restricted to particular machines. To make the programs easier to write, and to overcome the problem of intercommunication between different types of computer, software developers designed high-level languages which are closer to human languages, they use forms resembling English.

Here are some examples:

- FORTRAN was developed by IBM in 1954 and is still used for scientific and engineering applications.

- COBOL (Common Business Oriented Language) was developed in 1959 and mainly used for business applications.

- BASIC was developed in the 1960s and was widely in microcomputer programming because it was easy to learn; Visual BASIC is a modern version of the old BASIC language, now used to build graphical elements such as buttons and windows in Windows programs.

- PASCAL was created in 1971.It is used in universitiesto teach the fundamentals of programming.

- C was developed in the 1980s at AT& T. It is used to write system software, graphics and commercial programs. C++ is a version of C which incorporates object-oriented programming: the programmer concentrates on particular things (a piece of text, a graphic or a table, etc.) and gives each object functions which can be altered without changing the entire program. For example, to add a new graphics format, the programmer needs to rework just the graphics object. This makes programs easier to modify.

- Java was designed by Sun in 1995 to run on the Web; Java applets are small programs that provide animation and interactive features (let you play music and games) on web pages.

Programs written in high-level languages must be translated into machine code by software called a compiler or an interpreter. A compiler translates the source code into object code - that is, it converts the entire program into machine code in one go. On the other hand, an interpreter translates the source code line by line as the program is running.

It is important not to confuse programming languages with markup languages, used to create Web documents. They use instructions, known as markups tags, to format and link text files. Examples are:

- HTML which allows us to describe how information will be displayed on web pages.

- XML which stands forExtensible Markup Language.While HTML uses pre- defined tags, XML enables us to define our own tags; it is not limited by a fixed set of tags.

- Voice XML which makes Internet content accessible via voice recognition and phone. Whereas HTML is used to create visual applications, Voice XML is used to create voice applications that run on the phone. Instead of using a web browser on a PC, you use a telephone to access voice-equipped websites. You just dial the phone number of the website and then give spoken instructions, commands, and get the required information.

Exercises to the subject:

I. Read the text again and answer these questions.

1. Do computers understand human languages? Why? Why not?

2. What is the function of an assembler?

3. Why did software developers design high-level languages?

4. Which language is used to teach programming techniques?

5. What is the difference between a compiler and an interpreter?

6. Why are HTML and Voice XML called markup languages?