Time-Sharing Operating Systems

  Time-Sharing Operating Systems –   

The time sharing operating system works on the multiprogramming concepts where multiple jobs are executed at the same time through switching them frequently. This switching is very fast so that the users can interact with each program while it is running without realizing that the system is being shared.

Time sharing systems employ an interactive (or hands-on) computer system to enable straight communication between the system and the user. Here interactive means that the user will give the instructions to the system or program directly using an input device and the system will generate the results immediately on the output devices. The generation of the results consume very less time and its response time have to be short less than one second.

The time sharing operating system enable sharing of the computer resources to the multiple users at the same time. It requires less CPU time for each user as each command or action existing in a time shared system is short. The time shared systems employ a strategic CPU scheduling and multiprogramming to give each user a little amount of time shared system. Each user deals with at least one separate program in memory and which is known as a process while execution. It reduces the idleness of the CPU.

feature of operating system:-

• Time sharing is a logical extension of multiprogramming.
• multiple jobs are executed simultaneously by switching the CPU back and forth among them.
• The switching occurs so frequently that the users can not identify the presence of other users or program.
• users can interact with his program while it is running in timesharing mode.
• processors time is shared among multiple users. an interactive or hands on computer system provides online communication between the user and the system.
• A time shared OS uses CPU scheduling and multiprogramming provides each user with a small portion of a time shared computer. Each user has at least one separate program in memory.
• A  time shared operating system allowed many users to share computer simultaneously. since  each action or command  in a time shared system tends to be short only a little CPU time is needed for each user.

Advantages :-

• easy to use
• user friendly
• Quick response time

Disadvantages :-

• Reliability problem.
• One must have to take of security and integrity of user programs and data.
• Data communication problem.

Multiprogramming OS

• Multiprogramming operating system has ability to execute multiple programs with using of only one processor machine. 
• when two or more programs are residing in memory at the same time then sharing the processor is referred.

• multiprogramming assumes a single shared processor.

• multiprogramming increase CPU utilization by organizing jobs so that the CPU always has one to execute.

• the operating system keeps several job in memory at a time.

• this set of jobs in a subset of the job pool.

• the operating system picks and being to execute one of the job in the memory.

• multiprogramming operating system monitors the state of all active programs and system resources using memory management program to ensures that the CPU is never idle unless there are no jobs

• Example:-
• -Windows O/S
• -UNIX O/S
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• JOB:-In systems using multiprogramming a program loaded to memory and ready to execute is called a  job. 

 Execute another job while waiting for I/O:- The simple idea is to always have one job execute on the CPU by changing job when an I/O request is made.

States:- in a multiprogramming system , a job can be in one of three state.

Running

The job is currently executing on the CPU. At any time, at most one job can be in this state.

Ready

The job is ready to run but currently not selected to do so.

Waiting

The job is blocked from running on the CPU while waiting for an I/O request to be completed.

Advantages

• High and efficient CPU utilization.
• User feels that many programs are allotted CPU almost simultaneously.
• Resources are utilized smartly.
• Less response time.
• Short time jobs are done fastest compare to long time jobs.
• Multiple users can use multiprogramming system at once.
• It can help to improve turnaround time for short jobs.
• It reduces total read time that is required to execute a job.
• Multiprogramming system helps to optimize total job throughput of computer.
• Multiprogramming system can monitor fastest as entire tasks run in parallel.

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Disadvantages

• CPU scheduling is required.
• To accommodate many jobs in memory, memory management is required.
• If, it contains massive load of jobs then its long time jobs have to need long waiting time.
• Harder task is to manage of all processes and jobs.
• It is highly complex and sophisticated.

 

Batch Operating system

Batch Operating system 

• the users of batch operating system do not interact with the computer directly.

• Each user prepares his job on an offline device like punch card and submit it to the computer operator.

• To speed up processing , jobs with similar needs are batched together and run as a group.

• thus the programmers left their program with the operators.
• the operator then sorts programs into batches similar requirement

      

    Advantages:

 Same jobs in the batch are higher executed speed.

• A process is complete its execution, next job from job spool get executed without any user interaction.

•  CPU utilization gets improved.

• To speed up the processing speed, the batch process can partition into the number of processes.

Disadvantages:

• Difficult to debug.

• If a job gets to enter in an infinite loop, other jobs wait for unknown time.

• Batch systems are costly.

First Generation of operating system

definition :- operating system is a software program located between the computer user and acts as an interface between the application program and the computer hardware.

Generation of operating system

first generation(1940-1956) vacuum tubes

-used vacuum tubes for circuitry and magnetic drums for memory.

-taking up entire rooms.

-very expensive to operate.

-computer relied on machine language.

-in addition to using a great deal of  electricity , generated a lot of heat , which was often the cause of malfunctions.

-the lowest level programming language understood by computer to perform operation and they could only solve one problem at a time.

-inputs are based on punched cards and paper tape and output was displayed on printouts.

E.G.:- UNIVAC and  ENIAC computer.

Important concept ordinary differential equations

Differential equation

An equation involving independent variables, dependent variable and derivatives of dependent variable with respect to the independent variable is called a differential equation

Eg- (dy/dx)+y=xe^x

(d²y/d²x)+y=0

Exact differential equation

The necessary & sufficient condition for the differential equation Mdx+Ndy=0 to be exact is dM/dy=dN/dx.

Questions=[cos x tan y+cos [x+y]]dx+[sin x sec²y+ cos[x+y]]dy=0

Answer:-

Step 1:- given equation compare with M dx +N dy=0;

Step 2:-here,  M & N.

Step3:- dM/dy, dN/dx

Step4:- dM/dy=dN/dx(given equation is exact)

Step5:-then its solutions

 

All questions solve this given step by step