Multi-User Operating System

An operating system is software that acts as an interface between the user and the computer hardware which does multiple functions such as memory management; file management and processor management. The operating system should have to meet the requirements of all its users in a balanced way so that if any problem would arise with a user, it does not affect any other user in the chain. 

In a multiuser operating system, multiple numbers of users can access different resources of a computer at the same time. The access is provided using a network that consists of various personal computers attached to a mainframe computer system. A multi-user operating system allows the permission of multiple users for accessing a single machine at a time. The various personal computers can send and receive information to the mainframe computer system. Thus, the mainframe computer acts as the server and other personal computers act as clients for that server.

Components of the multi-user operating system:

1. Memory:  Consists of main memory (RAM). Main memory is determined as an important part of the operating system because it specifies how many programs may be executed simultaneously. The system can correct data that is present in the main memory, therefore every program that is executed must be copied from physical storage.
   The types of physical storage:
   • Hard disk: Hard disk can hold a huge amount of data and also determines how many programs can be run at a single time.
   • Floppy disk: It is more inexpensive, but it is potable 
   • Optical disks: They use a laser to read and write data. They can hold large data and portable 
   • Tapes: They are expensive but they can hold a huge amount of data. 
2. Kernel: This component is embedded in the computer system's main memory and may interact directly with the system's hardware. The multi-user operating system uses the kernel component at a low level, it is written in a low-level language.
3. Processor: The core of the computer is called the central processing unit (CPU).
4. Device handler: The device handler's primary goal is to provide all requests from the whole device request queue. The device handler operates in continuous cycle mode, first discarding the I/O request block from the queue side. The concept that is behind the handler is a queue where we follow the first in first out (FIFO) principle. 
5. Spooler: Simultaneously peripheral output on line. The spooler runs all computer processes and outputs the results at the same time.
6. User interface: Create a simple environment for all users for using the computer system. It is the point of communication between users and hardware (or) software. The main frame is one of the systems which works on the concepts of multi-user programming concept. It is widely used in banks, to store bank account and transaction details. This mainframe helps in various ways: security and scalability. 

Types of Multi-user Operating Systems: 

The multi-user operating systems is of the following types: 

1. Distributed System
2. Time sliced system
3. Multiprocessor system

Distributed system: 

The distributed operating system also known as distributed computing is a collection of multiple computers located on different computers. Communicate and coordinate their actions by passing messages to one another from any system. These all systems emulate a single coherent system to the end user. The end user will communicate with them with the help of the network. This system is divided in a way that multiple requests can be handled and in turn, the individual request can be satisfied eventually.

Examples: Electronic banking, Mobile apps

Time-sliced system: 

It is the system where each user talk is allocated to a short span of cpu time. A small time duration is allotted to every task. CPU time is divided into small time slices, and one time is assigned to each other. The decision to run the next piece of the job is decided by the schedule. This schedule executes the run instructions that need to be executed. The user can take turns and thus the operating system will handle the user's request among the users who are connected. This feature is not applicable in the single-user operating system. They use the mainframe system concurrently

Example: Mainframe, a partial exam of the time-sliced system. 

Multi-processor system: 

It involves multiple processors at a time. Enhance the overall performance. If one processor fails other continues working. Example: Spreadsheets, Music player

Features:

The multi-user operating system has the following features:

• Resource sharing: This maps to time slicing, multiple peripherals such as printers can be shared different files or data.
• Time-sharing
• Background sharing
• Invisibility: Many functions of multi-user operating systems are invisible to the user.

Advantages:

• It helps in the sharing of data and information among different users.
• It also helps in the sharing of hardware resources such as printers.
• It avoids disruption if any one computer fails it does not affect any other computer present on that network.
• Users can share their work with other users.
• The multi-user operating system is very helpful in economic improvement.
• Backing up data can be done in the multi-user operating system.
• The services of the multi-user operating systems are very stable and systematic.

Disadvantages:

• It requires expensive hardware to set up a mainframe computer 
• When multiple users log on or work on the same system it reduces the overall performance of the system.
• Information is shared with the public so privacy becomes a concern here.