Programming Languages. Generations of computer systems. Computer networks

assembly language is the most machine-dependent language used by programmers today. A disadvantage of assembly language is that it requires the use of an assembler to translate a source program into object code, or program.

High level programming languages are languages in which each instruction or statement corresponds to several machine code instructions. High level languages allow users to write in a notation which are familiar to them; for example. Fortran in mathematical notation. Cobol in English. So, high level languages are oriented to the problem, and low level languages are oriented to the machine code of a computer. Fortran is an acronym for FORmula TRANslation. It is used mostly for scientific purposes. PL/1 is a general-purpose programming language which is used primarily on large mainframes. ALGOL is an acronym for ALGOrithmic Language. It was developed as international language for the expression of the algorithms between individuals as well as programming language. It is a problem oriented high level language for mathematical and scientific use.

Some programming languages are applied only with a particular model of a computer; some are used more widely. From the programmers point of view the most useful language is one that can be used with several models of computers.

Software

Software is a term used in contrast to hardware to refer to all programs, which can be used on a particular computer system. By intelligent use of available software the user of a computer can considerably reduce the effort that is required m devising a system and writing the programs required to implement it.

We might list basic types of software as follows.

Subroutines are the smallest items of software. These are usually routines devised to perform large number of routine calculations, editing data for input and output.

Assemblers and compilers are programs used to convert programs written by symbolic language into machine code required by the computer.

Executive programs and operating systems are programs, which are held permanently in store and used to control the operations of other programs, particularly in multiprogramming systems.

Generators are programs, whicn are similar in action to compilers and assemblers but only object programs of a particular type can be produced from them.

Utilities programs are programs devised to perform some of the basic data handling operations, such as file conversion, sorting, controlling the location of data in a direct access file. Utility programs are generally devised for each unit.

Debugging routines include programs for producing print-outs of memory at various stages of a program, and also various forms of analysis of the progress of a program. Such programs are known as trace or monitor routines.

File processing programs are programs devised for performing operations on data files, such as editing, validation, comparing and updating.

I should like to add that data bases are also considered to be the computer software. A collection of data designed to be used by  different programmer is called a data base. In reality the data base is a collection of data tiles.

GENERATIONS OF COMPUTER SYSTEMS

The first generation computers were produced in 1950. They were very big. Some of them were as large as a whole room or even a whole building. They required a power supply and consumed much electric power. During their operation the 1-st generation computers were over heated and they had to be cooled. So, they were very expansive. Besides they were slow in operation. They perform one operation at a time, that is, they were based on the serial data processing. Therefore the scientists try to make a faster computer and they develop the faster computer. The second generation computers appeared in the late 1950s. They used transistors instead of vacuum tubes and their memories were made of magnetizable cores. Their size was reduced and their reliability was improved significantly