Types of Operating System

Mainframe Operating Systems: 

• A mainframe with 1000 disks and thousands of gigabytes of data is not unusual. Mainframes are normally used as web servers, servers for large-scale electronic commerce sites etc. 
• The operating systems for mainframes typically offer three kinds of services: batch, transaction processing, and time sharing. 
• A batch system is one that processes routine jobs without any interactive user present.  For example, claim processing in an insurance company
• Transaction processing systems handle large numbers of small requests per second; for example, check processing at a bank or airline reservations. 
• Timesharing systems allow multiple remote users to run jobs on the computer at once, such as querying a big database. 
• These functions are closely related: mainframe operating systems often perform all of them. An example mainframe operating system is OS/390, a descendant of OS/360

Personal Computer Operating Systems: 

• Job of personal computer operating system is to provide a good interface to a single user. They are widely used for word processing, spreadsheets, Internet access etc. 
• Personal computer operating systems are so widely known to the people who use computers but only few computer users knows about other types of operating systems. 
• Common examples of PC operating systems are Windows 2008, Windows 2007, the Macintosh operating system, Linux, Ubuntu etc. 

Server Operating Systems: 

• Server operating systems run on servers, which are very large personal computers, workstations, or even mainframes. 
• They serve multiple users at once over a network and allow the users to share hardware and software resources. Servers can provide print service, file service, or Web service. 
• Internet providers run many server machines to support their customers and Web sites use servers to store the Web pages and handle the incoming requests. Some Examples of typical server operating systems are UNIX and Windows 2007 server, Sun Solaris etc.

Real-Time Operating Systems: 

• Another type of operating system is the real-time system. These systems are characterized by having time as a key parameter. 
• Deadline slip may cause huge disaster sometimes. Two Types: hard real-time system,  soft real-time 
• If the action absolutely must occur at a certain moment (or within a certain range), we have a hard real-time system. For example, if a car is moving down an assembly line, certain actions must take place at certain instants of time, if a welding robot welds too early or too late, the car will be ruined
• Another kind of real-time system is a soft real-time system, in which missing an occasional deadline is acceptable. Digital audio or multimedia systems fall in this category.

Time Sharing Systems:

• Time sharing is a technique which enables many people, located at various terminals, to use a particular computer system at the same time. 
• Time-sharing or multitasking is a logical extension of multiprogramming. Processor's time which is shared among multiple users simultaneously is termed as time-sharing. In Time-Sharing Systems objective is to minimize response time.
• Multiple jobs are executed by the CPU by switching between them, but the switches occur so frequently. Thus, the user can receives an immediate response.