DATA STRUCTURE

Q. Explain the real time operating system.
Ans: Real time operating system: A real time operating system is a computer system that requires not only that the computing result be “correct” but also that the result be provide within a specified deadline period. Result produced after the deadline has passed even if correct may be of no real value.
A real system has well- defined, fixed time constants. Processing must be done within the defined constrains, or the system will fail.
Figure is as follows
Q. Batch Processing system.
Ans: In a batch processing system data are collected from the user for a few times and store them in memory. After certain time in the OS process the data sequentially as first come first survey base. It is also known as sequential, serial, off-line mode system.
Fig of a batch system is as follows.

Q. Multi Programming System.
Ans: A multiprogramming operating system increase CPU utilization by organizing jobs (code and data) so that the CPU always one to execute.
The OS keeps several jobs in memory simultaneously. This set of jobs can be a subset of the jobs kept in the job pool which contains all jobs that enter the system. Since the number of jobs that can be kept simultaneously in memory is usually smaller then the number job that can be kept in the job pool. The OS picks and begins to execute one of the job in memory. Eventually the job may have to wait for some task, such as an I/O operation to computer.
Multiprogramming system provide an environment in which the various system resource are utilized effectively, but they do not provide for user interaction with the computer system.
1. Uni-processor system.
2. More then one programs runs at a time parallel.
3. FCFS (First come first serve)
4. Multi programming increases utilization by organizing such that the CPU always has one to execute.
5. The OS keeps several jobs in the memory at a time.
Figure of multiprogramming OS structure.


Q. Time sharing OS.
Ans: Time sharing is a logical extension of multiprogramming system. The CPU executes multiple jobs by switching among them but the switches occur so frequently that the user can interact with each program while it is running.
A time shared operating system allows many users to share the computer simultaneously. Each action or command in a time shared system tends to be short, only a little CPU time needed for each user.
A time shared OS uses CPU scheduling and multiprogramming to period each user with a small portion of a time shared computer. Each user has a least one separate program in memory. A program loaded into memory and executing is commonly referred.
When a process executes it typically executes for a short time before it is either finished or need to perform I/O. I.O may be interactive. i.e. output is to display for user and input is from keyboard, mouse or other device.