What is an operating system? What are the examples of operating system?
One can simply defines an operating is an interface between user and computer!
What is interface?
An interface is nothing but a mediator between hardware and user. Also we can say that an operating system is nothing but set of programs which will understand our commands and passes them to hardware devices.
What do mean my installing OS(for example Windows)? What inside Windows compact disk(cd)?
Windows is nothing but operating system program which acts an interface between user and computer. Windows cd contains set of programs. Installing Windows OS means u r installing all the programs from compact disk to secondary storage device. Windows cd contains number of programs which work together and provide services to users.
When the system is in power off state , Operating system is just a static program stored on a secondary storage device like hard disk. When the power on operating system(set of programs) will be loaded from secondary storage device to main memory(RAM). Once Operating system is loaded into the main memory then Operating System will take the responsibility of loading and executing user programs.For example if u click on notepad or any program will be brought to main memory by Operating system. Operating system will take the control of CPU once it is loaded in to the main memory.
Who brings Operating System in to main memory?
Who brings Operating System in to main memory?
Have you noticed that it takes time to come windows screen when u power on ? Ya in that time operating system will be loaded in to memory.
BOOTSTRAP LOADER is a program whose only task is loading Operating System from secondary storage device to main memory.
Where is this BOOTSTRAP LOADER present?
Where is this BOOTSTRAP LOADER present?
When you are talking about main memory you are categorising it in to two parts.
RAM- Random Access Memory which is volatile and the program to be executed must be brought in to RAM.
ROM-Read Only Memory which is non volatile and permanent storage.
BOOTSTRAP LOADER will be in ROM. When the system is power on the BOOTSTRAP LOADER program will be invoked first and this program brings operating system program from secondary storage device to main memory. So once Operating System is loaded in to main memory then is takes control of the system.
Operating system is responsible for the following activities:
- Process Management
- Device Management
- Information management
- File Management
- Input/Output Management etc
Categorisation of Operating Systems:
An operating System can be categorised in to different types based on how many tasks it can do at a time and how many number of users using the same system at the same time.
Single Task Single User Operating System
For example consider MS DOS, at a time a system can execute only one task(command) at a time. Also only one user is allowed to use the system at a time.
Multi Tasking Single User Operating System
For example consider Microsoft Windows multiple tasks can be executed at the same time. You can open notepad, paint and word document and also at the same time you can send mail to your friend in Windows. Only one user is allowed to use the system at the same time.
Multi Tasking Multi User Operating System
At a time a system can execute multiple tasks at the same time and also multiple users can use the same system at a time. Linux flavors like Red Hat , UBUNTU are examples of multi tasking and multi user operating system .
Note: even though Windows Server Operating system is available which serves multiple users at the same time but the best example of multi user operating system is UNIX/LINUX.
Note: LINUX is a flavor of UNIX. LINUX code works similar to UNIX but still its code is different from UNIX. LINUX is a free open source software. That's why most of the companies using LINUX Operating System as their server Operating System.Also LINUX is virus free operating system. Installation cost is less.
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