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Batch operating system:
The users of a batch operating system do not interact with the computer directly. Each user prepares his job on an off-line device like punch cards and submits it to the computer operator. To speed up processing, jobs with similar needs are batched together and run as a group. The programmers leave their programs with the operator and the operator then sorts the programs with similar requirements into batches.
Time-sharing operating 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.
Distributed operating System:
Distributed systems use multiple central processors to serve multiple real-time applications and multiple users. Data processing jobs are distributed among the processors accordingly.
Network operating System:
A Network Operating System runs on a server and provides the server the capability to manage data, users, groups, security, applications, and other networking functions. The primary purpose of the network operating system is to allow shared file and printer access among multiple computers in a network, typically a local area network (LAN), a private network or to other networks.
Real Time operating System:
A real-time system is defined as a data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment. The time taken by the system to respond to an input and display of required updated information is termed as the response time. So in this method, the response time is very less as compared to online processing.
Hard real-time systems:
Hard real-time systems guarantee that critical tasks complete on time. In hard real-time systems, secondary storage is limited or missing and the data is stored in ROM. In these systems, virtual memory is almost never found.
Soft real-time systems:
Soft real-time systems are less restrictive. A critical real-time task gets priority over other tasks and retains the priority until it completes. Soft real-time systems have limited utility than hard real-time systems. For example, multimedia, virtual reality and Advanced Scientific Projects like undersea exploration and planetary rovers, etc.

Hi,
Mechanical engineering is known as the evergreen branch among all the other branches of engineering. Traditionally, mechanical engineers have to deal with concepts such as mechanics, thermodynamics, robotics, kinematics, structural analysis and fluid mechanics with their applications in automotive sector, power sector, refrigeration and air conditioning sector, aerospace.
Now-a-days the scope of mechanical engineering is expanding beyond its traditional boundaries and is more of inter-disciplinary in nature. Mechanical engineers are focusing their attention towards new areas such as nanotechnology, development of composite materials, biomedical applications, and environmental conservation. With this shift in paradigm the new job avenues have been opened for the mechanical engineers.
On the other hand, I would suggest you to pursue computer Science engineering with diverse specializations. If you go for computer Science engineering, you will get really worthy salary packages, avenues to go abroad and you can work anywhere. Computer Science has a very wide scope. Indian IT companies such as Wipro, Infosys, TCS, Patni, HCL, etc. have been able to garner gains even during the recession and have hired a number of computer professionals. Even the MNCs look for good computer engineers from India.
A few college recommendations for you are:
• IITs
• Bengal Institute of Technology, Karnataka
• UTM, Shillong