Introduction
Kernel, command processor, shell, and graphical user interface (GUI) are the main components of OS.
Kernel
The kernel is known as the control module of an OS. The main working of kernel in the OS is to decide which part loads first in the processor and which remains in the main memory. In simple words, kernel decides which process should be allocated to the processor to execute first and which process to be kept in the main memory to be executed next. All this is happening, because kernel is present in the memory due to which the size of kernel is small as possible. Kernel is responsible for providing all the essential services which are required by other parts of the operating system and user applications. Memory management, process management, task management, and disk management, all these are the responsibility of a kernel. System hardware is connected to the application software with the help of kernel. Between the system hardware and user applications, kernel acts as an interface. It decides the state of incoming processes. Kernel is responsible to manage communication between software (user–level applications) and hardware (CPU) and disk memory.
Command Processor
The part of the operating system which receives and executes the commands of the operating system is known as command processor. As soon as the command prompt is displayed, command processor waits for the command. Whenever the command is entered, the command processor first analyses the syntax and then confirms that the command is valid is not. If the command is valid then it executes it, if it is invalid then it gives an error message. The command processor first interprets the mouse operations and then executes the appropriate command, for OS with GUI. The other name of command processor is command line interpreter. Command processor is present in every operating system. This is a very important tool of OS.
Shell
Shell is known as the outermost layer of the operating system. Shell holds a programming language which not only controls the processes and files but also controls the other programs. Shell is said to be an exclusive feature of UNIX. It accepts the command line inputs and expands wild cards, aliases, etc., and it executes the program which is in the processing. With command line interpreter and line editor, shell is also known as language with variables, arrays, functions, and control structures. These command lines can be put into a file for execution. These files are known as shell scripts which can be quickly written and tested and should be tried in association with other standard UNIX.
Graphical User Interface
Because of GUI (Graphical User Interface), the user doesn’t need to remember the long syntax of the command language, they point to the option with mouse, make the selection of commands and can perform their job. It is not difficult to understand in actuality because the command processor executes all the selected commands in the background. GUI gives relief to the user from the burden of remembering the commands. GUI is responsible for the visual representation of communication presented to the user for easy interaction with the machine.Communication can be performed by interacting with the graphical elements like buttons and icons rather than the usual text–based or command–based communication.
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Services provided by an Operating System
The following services are provided by the operating system which is given below,
- Process management service
- Main – memory management service
- File management service
- I/O operations management service
- Network management
Process Management
In this service, OS manages the creation, deletion, and suspension of system processes well as user processes. It handles the process synchronization, interprocess communication as well as deadlocks.
Main –Memory Management
This service is responsible for the allocation of memory, when it is required by any device as well as deallocation of memory, when it is not in the use. It keeps a record of memory space i.e., how many are used and how many are not used. If the space is available in the memory then, it decides what process is loaded into the memory.
File Management Service
The handling of creation and deletion of files and directories comes under this service. It provides security to the files. It is also responsible for wrapping files into secondary storage.
I/O Operation Management Service
The user is unable to know about the internal details of the devices (hardware) of the system during the communication between the user and the system. The operating system hides these details from the user. Only device driver knows the internal details of the particular device (hardware) for which it has been designed. Device driver is a system program that allows the operating system to communicate and recognize with the hardware.
Network Management
This service is capable of finding out the errors occurs in the CPU, memory, I/O devices or in a user program and report them to the system. Such errors are memory errors which are occurred due to illegal access of the memory or memory location, due to the infinite loops in a user program, etc.
Summary
In this article, we learned the architecture of the operating system. We see the different components of the operating system architecture like kernel, command processor, shell, and graphical user interface. Kernel decides which process should be allocated to the processor to execute first and which process to be kept in the main memory to be executed next. Command processor receives the command and executes them. Shell is the outermost layer of the operating system which controls the processes, files and programs. GUI helps the user to perform the programs without remembering the long commands.
Then we studied the five services provided by the operating system. Operating system provides process management service, main – memory management service, file management service, I/O operations management service, network management. All these services have their own duty.