Software is a collection of programs designed to solve problems on a computer. A program is an ordered set of commands. Software and hardware work interconnected and in continuous interaction. Any hardware device is controlled by software.

Software can be divided into three classes: system software, application software and tool software. This classification is rather tentative. Integration of software has led to the fact that almost any program has features of each class.

System software is intended for managing a computer, distribution of its resources, dialogue support with users, help in computer maintenance and also for partial automation of new programs development.

The system software is a set of programs many of which are supplied with the computer and its documentation. System software can be divided into three main parts: operating systems (OS), programming systems and service programs.

The main components of the system software are: operating systems that solve the problem of interconnected functioning of individual components.

There are 4 types of operating systems:

batch processing operating systems: relatively high speed of logical and automatic operations, but in turn had input and output speed of the processor load by 20 – 30%.

operating system with the distribution of tasks in time (organized by the input and output queue of tasks, and served up to 15 users and the processor loaded to 80-90%).

real-time operating system, used to control various processes.

The system software manages the work of the computer system. As a rule, system software provides the interaction of other programs with hardware components, the organization of the user interface. This includes operating systems and service systems.

Applied software is designed to solve applied problems of human professional activity (that is, attached to the practice). The range of such programs is extremely wide: from production and scientific training and entertainment. This includes calculation, training, simulation programs, computer games, etc.

Tooling software is intended for development of all kinds of information software. In this case, under the information software we understand a set of pre-prepared data necessary for the work of the software. For example, any modern program has a built-in help for work with this program. The help file is an information software. To the instrumental software include: editors (text, graphic, music), tabular data processing systems (tabular processors), database management systems, translators of programming languages, integrated business systems, etc.

Programming systems are designed to facilitate and to partially automate the process of program development and debugging. The main components of these systems are translators of high-level languages, such as Pascal, C, Basic, etc. A special role belongs to the Assemblies. A program in Assembly language is called machine-oriented. Assembly languages are usually used by system programmers.

Translators perform conversions of programs from high-level languages to machine language. In addition, translators of course carry out syntactic analysis of the program being translated. They can also inhibit and optimize the programs they receive, produce documentation for the program, and perform a number of other service functions.

Assemblies turn programs that are presented in machine-oriented languages into machine language.

Service programs extend the capabilities of the OS. They are, of course, called utilities. Utilities allow, for example, to check the information in the shistnadtsatkovogo code, which is stored in individual sectors of magnetic disks; organize output to the printer text files in a particular format, perform archiving and unarchiving files, etc.

The structure of applied software can be divided into general-purpose and special-purpose application programs.

General-purpose application software is a set of programs that are widely spread among various categories of users. The most famous among them are: text editors, graphics systems, spreadsheets, database management systems, etc.