Operating Systems : Types of Operating Sytems

Types of Operating Systems

1. Simple Batch

2. Multi-programmed Batched

3. Time-Sharing

4. Personal Computer

5. Parallel

6. Distributed

7. Real Time

8. Mobile

1. Simple Batch

- No user interaction

- Job is prepared and submitted to the CPU. A job consists of the program, data and information about flow of control. 

- For reducing setup time, similar tasks / jobs are batched together and are run in group. 

- The batched jobs are executed one after the other automatically. 

- Output (including a log of errors, if any) is returned to the programmer. 

- Turnaround time : delay between job submission and job completion

- Large turnaround time was usually due to the slow nature of mechanical I/O (input/output) devices as compared to the presently used electronic devices. This also led to CPU being idle for a major part of time.

2. Multiprogrammed Batch

- To increase efficiency, CPU usage is maximised to reduce time spent idle by CPU.

- To keep the CPU engaged at all times, several programs can be allowed to run. When one program uses I/O devices, then CPU can execute another program instead of waiting for the I/O operations to complete.

- OS has to manage the operation of all jobs and switch jobs between their operations. Ex - if one job utilises the input terminal, and the CPU is idle, OS assigns the CPU to another job.

- Multiprogramming increases CPU utilisation by ensuring that the CPU does not remain idle for a long time.

- Programs do not run concurrently / simultaneously. The jobs are scheduled, and they accordingly get their CPU time, while other jobs wait or utilise other resources.

3. Time Sharing

- Also known as Multitasking systems, as tasks are executed simultaneously.

- Frequent switching between multiple interactive programs enables users to interact with each program.

- User Interaction is possible.

- Jobs residing in main memory are sent to the processor. If the job is currently in I/O phase, another job is supplied to the CPU, keeping the CPU busy.

- Main difference between time sharing and multi programming is that time sharing is interactive, while multi programming supports no user interaction. 

4. Personal Computer

- Supports single user

- Responsive and user friendly

- Maximum CPU utilisation not a primary goal

- Ex : Windows, Linux Operating Systems etc.

5. Parallel

- Also known as multiprocessor systems

- Multiprocessors - use more than one CPU

- CPUs have shared memory and clock

- Primary concern is managing resources of parallel systems

- Increased throughput - more work done in lesser time

- Cost effective, as multiple users require shared resources such as I/O devices

- Also known as "tightly-coupled" systems

6. Distributed

- Also known a "loosely-coupled" system

- Computation distributed among several physical processors

- Each system has its own OS and processor

- Communication occurs between different processors through bus etc.

- Enables file sharing and communication between systems

- Reliability is increased and computation is also sped up through load sharing between different systems

7. Real Time

- Used for real time applications such as display systems, industrial systems, scientific experiments etc.

- Well - defined fixed time constraints

- Mostly used for controlling devices such as those which use sensors

8. Mobile

- Operating Systems for the mobile interface

- Used in handheld devices such as phones, tablets, PDAs

- Multitasking, user interaction enabled 

- Ex : iOS, Android, Windows (for Phones), Bada etc. 

Introduction

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operating-systems, programming

Saturday, 17 January 2015

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