A user of a computer system interacts directly with an application software program for his purposeful task. The task works over a platform, which is the operating system. The operating system initiated the execution of a task in units as per pre-defined instruction sets and the availability of the system's primary resources.
Operating System Important Concepts
The initializing of the task is known as a system call. The system calls delete, create, and use various software objects managed by the operating system. These software objects include:-
Process
Files
Pipes
System Calls
Kernel
The Shell
Throughput
Turnaround Time
Process
- A process is a program in execution. Each unit of execution or a process may be further broken down into even smaller units of execution.
- The process generates another process, which becomes it's a child.
- The structure of the processes thus created becomes a process tree.
The regeneration level of the process goes deep up to maximum 3-4 levels, but a deep level process for its fast and balanced execution can generate further sub-units called threads. So, the smallest unit of execution in any system is the thread.
As a process executes, it changes state-
New
The process is being created.
Running
Instructions are being executed.
Waiting
In this stage the process is waiting for some event to occur.
Ready
In this stage the process is waiting to be assigned to a processor.
Terminated
The process has finished execution.
Files
- Besides controlling various activities of different components of the system, it is the job of the operating system to store users data and programs permanently in secondary storage devices like floppy and hard disk.
- This is necessary because basically computer perform its activities using RAM, which is volatile in nature.
- This means all the data stored in RAM will be lost in case power loss occurs even for a fraction of second.
- Secondary storage devices are able to store information permanently, so users information or data can be stored in secondary storage devices so that they can be used in future.
- The information or data are stored in the form of files.
- Program is a set of instruction, so this is also needed to be stored permanently for future execution.
- Files are to be stored in proper manner so that they can be retrieved easily later.
- For this purpose, operating system uses tree like hierarchical structure to store the files.
- Files are used to store information only it cannot be used to store the information about other files like where they are stored.
- For this purpose, operating system uses the concept of directory to store information about files.
- Directory is used for grouping of files together.
- System calls are needed to create and remove directories and files.
- The storage of information in terms of files and directories is known as file system.
Pipes
- A pipe is a sort of file that can used to connect two processes together.
- These can be used for inter-process communication.
- When process a wants to send data to process B, it writes on the pipe as through it were an output file, process B can read the data by reading from the pipe as through it were an input file.
- Most of the modern operating systems like UNIX and DOS, support a concept of pipe, By the means of pipe, process can further information to other process that can be use the information for its processing and in the way doing the things user wanted.
System calls
- It is not always required that the user is directly interacting with the operating system for creating files, directories and for any other services required.
- User may use available application programs communicate with the operating system and request services from it by making system calls.
- Each system call requires certain parameters to be given using which operating system understands clearly as what is needed.
- If a system call cannot be carried out, either due to invalid parameter or a disk error, the operating system sets an error flag in its environment.
- Inspecting this error flag any application program may judge whether its request has been fulfilled or not.
- The operating system provides several systems calls for carrying out various activities like creating a file or directory, removing a file or directory, renaming a file, etc.
Kernel
- It is the central module of an operating system.
- It is the part of the operating system that loads first, and it remains in the main memory.
- Because it stays providing all the essential services required by other parts of the operating system and applications.
- Typically the kernel is responsible for memory management, process and task management, and risk management.
Shell
- The shell is the command interpreter for the operating system.
- The operating system receives commands from the user in English like language that the computer does not understand.
- It is the job of the command interpreter to interpret the instructions given by the user into machine understandable language.
- For example, the command interpreter for the MS-DOS operating system is command.com.
- We can say that the command interpreter is the interface between the user and the operating system.
- Command interpreter uses the system resources heavily, call other system calls to fulfill the user's requirements.
- Whenever we boot the system, it is the command interpreter that displays a prompt to the user, showing that the system is ready to receive users' commands.
Throughput
- It is the total volume of work performed by the system over a given period.
- More amount volume of work per unit of time considered will prove the efficiency and usefulness of the operating system.
Turnaround time
- Turnaround time defines as the interval between the time a user submits his job to the system for processing and the time he receives results.
- This is also known as Response Time.
- This is more crucial where different users share one system in a network, the number of users, the more load will be given on the operating system.
This post discusses the concepts of the operating system. I hope you have learned from reading this post. If you like this post then share it with your friends and you can comment on any of your doubts and I will replay then at the earliest.
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