Type of Operating Systems:

We can define four common Type of Operating systems according its functionality.

• Batch Processing System
• Multiprogramming System
• Multi Tasking / Time Sharing System
• Real Time System

 We can also Classified Operating System in following Two Type.

• Single Users Systems
•  Multi users System

Batch Processing System :
In Batch processing same type of jobs batch 
(BATCH- a set of jobs with similar needs) together and execute at a time. The OS was simple, its major task was to transfer control from one job to the next. The job was submitted to the computer operator in form of punch cards. At some later time the output appeared. The OS was always resident in memory. Common Input devices were card readers and tape drives. Common output devices were line printers, tape drives, and card punches. Users did not interact directly with the computer systems, but he prepared a job (comprising of the program, the data, & some control information).

Multiprogramming System:

Multiprogramming is a technique to execute number of programs simultaneously by a single processor. In Multiprogramming, number of processes resides in main memory at a time. The OS picks and begins to execute one of the jobs in the main memory. If any I/O wait happened in a process, then CPU switches from that job to another job. Hence CPU is not idle at any time. Figure depicts the layout of multiprogramming system. The main memory consists of 5 jobs at a time, the CPU executes one by one.

Advantages:

Efficient memory utilization

Throughput increases

CPU is never idle, so performance increases.

 

OS

Job 1

Job 2

Job 3

Job 4

Job 5

Multi Tasking / Time Sharing System:

Time sharing, or multitasking, is a logical extension of multiprogramming. Multiple jobs are executed by switching the CPU between them. In this, the CPU time is shared by different processes, so it is called as “Time sharing Systems”. Time slice is defined by the OS, for sharing CPU time between processes. Examples: UNIX, etc.

Real Time System:

Real-time operating systems were designed for two general classes of applications: event response and closed-loop control. Event response applications, such as automated visual inspection of assembly line parts, require a response to a stimulus in a certain amount of time. In this visual inspection system, for example, each part must be photographed and analyzed before the assembly line moves.

By carefully programming an application that runs on a hard real-time operating system, designers working on event response applications can guarantee that a response will happen deterministically (within a certain maximum amount of time). Considering the parts inspection example, using a general-purpose OS could result in a part not being inspected in time - therefore delaying the assembly line, forcing the part to be discarded, or shipping a potentially defective part.

In contrast, closed-loop control systems, such as an automotive cruise control system, continuously process feedback data to adjust one or more outputs. Because each output value depends on processing the input data in a fixed amount of time, it is critical that loop deadlines are met in order to assure that the correct outputs are produced. What would happen if a cruise control system failed to determine what the throttle setting should be at a given point in time? Once again, hard real-time operating systems can guarantee that control system input data is processed in a consistent amount of time (with a fixed worst-case maximum).

It should also be noted that many applications that must run for extended periods of time can benefit from the reliability that an RTOS can provide. Because real-time operating systems typically run a minimal set of software rather than many applications and processes at the same time, they are well suited for systems that require 24-7 operation or where down-time is unacceptable or expensive.

Single Users Systems:

Provides a platform for only one user at a time, they are popularly associated with Desk Top operating system which runs on standalone systems where no user accounts are required. Example: DOS

Multi users Systems :

Provides regulated access for a number of users by maintaining a database of known users. Refers to computer systems that support two or more simultaneous users. Another term for multi-user is time sharing. Ex: All mainframes and are multi-user systems. Example: UNIX