Compare and contrast a PC operating system and a NOS?

Answer 1

In order to support multiple concurrent users and to provide shared access to network services, resources, and devices, NOS servers must run operating systems with characteristics that extend beyond those of client PCs. A number of operating systems such as Linux, Windows NT/2000/XP, and Novell NetWare can integrate the features that are required to function as a NOS server.

A system capable of operating as a NOS server must be able to support multiple users concurrently. The network administrator creates an account for each user, allowing the user to connect to and logon to the server system. A user account on the server enables the server to authenticate the user and to allocate appropriate resources the user is allowed to access. Systems that provide this capability are called multiuser systems. UNIX, Linux, and Windows NT/2000/XP all support this multiuser capability.

A NOS server is a multitasking system. Internally, the OS must be capable of executing multiple tasks or processes at the same time. Server operating systems accomplish this with scheduling software that is built into the execution environment. The scheduling software allocates internal processor time, memory, and other elements of the system to different tasks in a way that allows them to share the systems resources. Each user on the multiuser system is supported by a separate task or process internally on the server. These internal tasks are created dynamically as users connect to the system and are deleted when users disconnect.

Another feature of systems capable of acting as NOS servers is the processing power. Ordinarily, computers have a single central processing unit (CPU) that executes the instructions which make up a given task or process. In order to work efficiently and deliver fast responses to client requests, an OS that functions as a NOS server requires a powerful CPU to execute its tasks or programs. Single processor systems with one CPU can meet the needs of most NOS servers if they have the necessary speed. To achieve higher execution speeds, some systems are equipped with more than one processor. Such systems are called multiprocessing systems. They are capable of executing multiple tasks in parallel by assigning each task to a different processor. The aggregate amount of work that the server can perform in a given time is greatly enhanced in multiprocessor systems. Servers of this nature are sometimes referred to as enterprise servers because of their capacity to handle large and multiple services. Enterprise servers are also capable of running concurrent copies of a particular command. This allows them to execute multiple instances of the same service or program call threads. A thread is a computer programming term that describes a program which can execute independently of other parts. Operating systems that support multithreading enable programmers to design programs whose threaded parts can execute concurrently.