Evolution of operating systems

History OS contains approximately half a century. It in many respects was defined and defined by development of element base and the computing equipment.

First generation.

The 40th years. The first digital computers without OS. The organization of computation process decides the programmer from the control panel.

The second generation.

The 50th years. Emergence of a prototype of OS - the monitor systems implementing batch processing system of tasks.

Batch mode

Need of optimal use of expensive computing resources led to emergence of the concept of "batch mode" of execution of programs. Batch mode assumes existence of queue of programs on execution, and OS can provide program load from external data media in RAM, without waiting for completion of execution of the previous program that allows to avoid idle time of the processor.

Third generation.

1965-1980. Transition to integrated circuits. IBM/360. Practically all main concepts inherent in modern OS are implemented: time sharing and multitasking, separation of powers, real-time scale, file structures and file systems. Implementation of multiprogramming demanded entering of very important changes into the computer equipment: the exclusive and user modes, means of protecting of areas of memory, the developed system of interruptions.

Time sharing and multitasking

Already batch mode in the developed option requires processor sharing between accomplishment of several programs. Need for time sharing (multitasking, multiprogramming) was shown even stronger at distribution as input/output devices of teletypes (and later, terminals with electron beam displays) (the 1960th years). As the speed of keyboard input (and even readings from the screen) given by the operator is much lower, than the processing speed of these data the computer, use of the computer in the "exclusive" mode (with one operator) could lead to idle time of expensive computing resources.

Time sharing allowed to create the "multi-user" systems in which one (usually) central processor and the block of RAM connected to numerous terminals. At the same time a part of tasks (such as input or editing data by the operator) could be performed in the dialog mode, and other tasks (such as massive calculations) — in batch mode.

Separation of powers

Distribution of the multi-user systems demanded the solution of the problem of separation of powers allowing to avoid a possibility of modification of the runtime program or data of one program in the memory of the computer another (containing an error or which is maliciously prepared) the program and also modification of the OS the application program.

Implementation of separation of powers in OS was supported by developers of the processors which offered architecture with two operation modes of the processor — "real" (in which all address space of the computer is available to the runtime program) and "protected" (in which availability of an address space is limited to range, selected at start of the program for execution).

Real-time scale

Use of multipurpose computers for management of production processes demanded implementation of "real-time scale" ("real time") — synchronization of execution of programs with external physical processes.

Inclusion of function of real-time scale in OS allowed to create the systems which are at the same time servicing production processes and solving other problems (in batch mode and (or) in time partitioned mode).

Such operating systems received the name Operating systems with planning in real time or in abbreviated form OSRV.

File systems and structures

Gradual replacement of carriers with sequential access (punched tapes, punched cards and magnetic tapes) drives of random access (on magnetic a disk)

Fourth generation.

End of the 70th. The working option of a stack of protocols TCP/IP is created. In 1983 it was standardized. Independence of producers, the flexibility and efficiency proved by successful work the Internet made this stack of protocols the main stack for the majority of OS.

Beginning of the 80th. Emergence of personal computers. Rapid growth of local networks. Support of network functions became a necessary condition. The 80th years. Fundamental standards on communication technologies of local networks are accepted: Ethernet, Token Ring, FDDI. It allowed to provide compatibility of network OS at the bottom levels.

Beginning of the 90th. Practically all OS became network. There were specialized network OS (for example IOS working in routers)

Last decade. Special attention to corporate network OS of which are characteristic high degree of scalability, support of network work, the developed security protections, capability to work in the heterogeneous environment, existence of means of the centralized administration.