Unix is a multiuser, multitasking operating system that was developed by Bell Laboratories in 1969. In a multiuser system, many users can use the system simultaneously. A multitasking system is capable of doing multiple jobs. Each user interacts with their own shell instance in this type of operating system and can start applications as required.An image that demonstrates the structure of the Unix operating system is −As seen in the image, the main components of the Unix operating system structure are the kernel layer, the shell layer and the application layer.Details about these are given as follows −KernelThe kernel provides ... Read More

Secondary storage devices are non-volatile devices where the data is stored for long-term storage. Disks are the mainly used secondary storage devices. They provide the bulk of secondary storage in operating systems today.The main activity that is performed in secondary storage management is disk scheduling. There are many disk scheduling algorithms. However, the important ones are FCFS scheduling, SSTF scheduling, SCAN scheduling and LOOK scheduling.All the disk scheduling algorithms are explained using the following requests for the disk -10, 95, 23, 78, 80First Come First Served SchedulingIn first come first served scheduling, the requests are serviced in their coming order. ... Read More

System programs provide an environment where programs can be developed and executed. In the simplest sense, system programs also provide a bridge between the user interface and system calls. In reality, they are much more complex. For example, a compiler is a complex system program.System Programs PurposeThe system program serves as a part of the operating system. It traditionally lies between the user interface and the system calls. The user view of the system is actually defined by system programs and not system calls because that is what they interact with and system programs are closer to the user interface.An ... Read More

Memory management plays an important part in the operating system. It deals with memory and the moving of processes from disk to primary memory for execution and back again.Some activities of an operating system with regards to memory management are −Memory AllocationA simple way to allocate memory is to provide the empty memory spaces to incoming processes as required. This can be done using the following algorithms −First-FitThe first available memory space that is large enough for the process purposes is allocated. Searching can start at the beginning or at the point where the last first-fit search ended.Best-FitThe smallest memory ... Read More

MS-DOS is an operating system created for personal computers. It was developed by Microsoft. It is a classic example of an operating system with a layered structure. MS-DOS operating system is split into various layers and each of the layers have different functionalities.Layering provides a distinct advantage in the MS-DOS operating system because all the layers can be defined separately and interact with each other as required. Also, it is easier to create, maintain and update the system if it is done in the form of layers. Change in one layer specification does not affect the rest of the layers. ... Read More

A process is an active program i.e a program that is under execution. It contains the program code, program counter, process stack, registers etc. Process Management deals with processes and the various mechanisms to handle them.The various activities that the operating system performs with regard to process management are mainly process scheduling and context switching. Details about these are given as follows −Process SchedulingThere are many scheduling queues that are used to handle processes. When the processes enter the system, they are put into the job queue. The processes that are ready to execute in the main memory are kept ... Read More

The operating system is split into various layers In the layered operating system and each of the layers have different functionalities. This type of operating system was created as an improvement over the early monolithic systems. Why Layering in Operating System? Layering provides a distinct advantage in an operating system. All the layers can be defined separately and interact with each other as required. Also, it is easier to create, maintain and update the system if it is done in the form of layers. Change in one layer specification does not affect the rest of the layers. Each of ... Read More

System programs provide an environment where programs can be developed and executed. In the simplest sense, system programs also provide a bridge between the user interface and system calls. In reality, they are much more complex. For example: A compiler is a complex system program.The user view of the system is actually defined by system programs and not system calls because that is what they interact with and system programs are closer to the user interface.An image that describes system programs in the operating system hierarchy is as follows −In the above image, system programs as well as application programs ... Read More

The entire operating system works in the kernel space in the monolithic system. This increases the size of the kernel as well as the operating system. This is different than the microkernel system where the minimum software that is required to correctly implement an operating system is kept in the kernel.A diagram that demonstrates the architecture of a monolithic system is as follows −The kernel provides various services such as memory management, file management, process scheduling etc. using function calls. This makes the execution of the operating system quite fast as the services are implemented under the same address space.Differences ... Read More

A microkernel is the minimum software that is required to correctly implement an operating system. This includes memory, process scheduling mechanisms and basic inter-process communication.A diagram that demonstrates the architecture of a microkernel is as follows −In the above diagram, the microkernel contains basic requirements such as memory, process scheduling mechanisms and basic interprocess communication. The only software executing at the privileged level i.e. kernel mode is the microkernel. The other functions of the operating system are removed from the kernel mode and run in the user mode. These functions may be device drivers, file servers, application interprocess communication etc.The ... Read More