The presence of operating systems is there from the very first computer generation. It has been evolving for the past decades. These are the few important types of operating systems mentioned below:

1. Batch Operating System: In this type of system, there is no direct interaction between the user and the computer. This is treated as the oldest type, as this user was required to submit all the processes of the same type in a batch.
2. Multiprogramming Batch Operating System: In a multiprogramming batch system, the operating system and central processing system always get busy in executing multiple jobs. Once the job needs an I/O operation, this OS switches to another job.
3. Multiprocessor Operating System: This type of system consists of several processors that share a common physical memory. It increases the speed of computing performance as several processors operate under a single operating system.
4. Distributed Operating System: The agenda of developing a distributed operating system is the availability of inexpensive and powerful microprocessors in communication technology. Low prices and performance ratio are the main advantages of this operating system
5. Real-time Operating System: It is an operating system, which gives the maximum time for each of the critical operations despite any buffering delays.

• Concurrency: It is used to manage multiple tasks that execute at the same time and share resources. It mainly includes context switching, synchronization, scheduling, deadlock and processes, and threads.
• Processes: Processes are the group of commands that are given to execute a program. A process has a virtual address space, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, executable codes, and one execution thread.
• Thread: A thread is a chain of commands within a process that is generally in order for execution. Threads also have their own security codes for protection or for keeping it safe. Threads are allocated to dispense their virtual space and system resources. Each thread also keeps a scheduling priority, exception handlers, thread-local storage, a unique thread identifier, and a set of structures that the system will utilize up till scheduled or set.
• Memory Management: It is a process that is used to control computer memory and offers a set of services such as dynamic address translation, virtual memory, linking, dynamic memory allocation, and demand paging.
• File Systems: It is a method of organizing and storing information on a computer hard drive. It covers several topics such as storage devices, disk management, and scheduling, directories, protection, and crash recovery.