Unix Architecture

The Unix system is established up of layers, within every layer representing a building block which could be used to build other building blocks and etc.  Many commands and programs supplied with the Unix system could be used in merging with each other to build another tools and complex mechanisms could be built up from a single line of commands to perform a vast assortments of functions.

The hardware at the middle of the diagram gives the operating system with the basic hardware services. The OS interacts straightly with the hardware, giving general services to insulating and programs them from hardware specifics.

Figure

The Unix operating system is generally known as Kernel. It gives an interface for all other Unix programs to use the hardware resources. That concept permits the higher level programs to be hardware independent. Whenever the user logs in to Unix communicates with the kernel by the shell program. That does not make itself available for the end user. The Kernel gives the basic services of Process management, System initialization, Memory management, Communication facilities, File System management and Programmatic interface by system calls.

Programs like as the shell and editors (ed and vi) which are display in the outer layers interact with the Kernel through invoking a well defined set of system calls. The kernel is instructed by the system calls to perform several operations for the calling program and swap of data among the the program and kernel.

One of the prominent characteristics of the Unix system is its huge variety of powerful utility programs. The utility can be used to locate system information, administer files or the contents of files and manipulate the output of other utilities.

The shell is a utility program which acts as a command interpreter. That is the main interface to the kernel. A Shell is also a command language as well as a programming language. As a command language it could be used to communicate interactively with the Kernel. As a programming language, the users can write shell scripts to solve the several problems.

Many programs display in the figure are in standard system configuration and are called as commands. Above 200 utility programs (commands) are supplied with Unix system. These are also used to solve the complex problems.

Further to  utility  programs, there  are  a  various number of  Unix-based application programs such as  spreadsheets, word processors, language processors and database managers that form the outer most ring in the architecture.