Real Time OS

Real Time OS: 

A real time system is often using as a control device in a dedicated application. Transducers and sensors bring data to the computer. The computer must analyse the data and possibly adjust controls to sensor inputs. Systems which control scientific experiments, medical systems, industrial controls systems and some display systems are the examples of real time systems.

Figure: Real Time OS

Time Sharing OS

Time Sharing OS: 

Time sharing is a mechanism to provide simultaneous, interactive use of a computer system by many users in such a way that each user in given the impression that he can his own computer. It uses multi-programming with a special CPU scheduling algorithm to achieve this. A time sharing system has many user terminals simultaneously connected to the same computer. Using these terminals, multiple users can simultaneously work on the system. Example: Windows 95/ 98/ 2000.

Figure: Time Sharing OS

Multi-programming OS

Multi-programming OS: 

Multi-programming is the interleave execution of two or more processes be a single CPU computer system. Here, jobs are broadly classified into the following two types:

1. CPU-bound jobs.
2. I/O-bound jobs.

Requirements of multi-programming system:

1. Large memory
2. Memory protection
3. Job status preservation
4. Proper job mix
5. CPU scheduling

Example: UNIX, IBM VM

Figure: Multi-programming OS

Multi-Processing OS

Multi-Processing OS: 

Multiprocessing is the simultaneous execution of two or more processes by a computer system having more than one CPU.
There are two types of multiprocessing systems. They are:

1. Tightly coupled system.
2. Loosely coupled system.

Example: Linux, windows

figure: Multi-Processing OS

Batch Processing OS

Batch Processing OS: 

The batch processing mechanism helped reducing the idle time of a computer cause transition from one job to another and not require any operator intervention. Example: MS-DOS

Figure: Batch Processing OS 

Different types of OS based on memory capacity, number of user, working principles and other features

Different types of operating system based on memory capacity, number of user, working principles and other features:

1. Batch Processing OS
2. Multi-programming OS
3. Multi-processing OS
4. Time Sharing OS
5. Real Time OS
6. Network OS

Difference between Text-Based OS & Graphic Based OS

Text-Based OS vs. Graphic Based OS:

Text based OS		Graphic based OS
Commands are given by text format	1		Commands are given by icon.
Commands are necessary to be memorized.	2		Commands are not necessary to be memorized.
It is not user friendly.	3		It is user friendly.
Less memory is needed for this.	4		More memory is needed for this.
Example: DOS	5		Example: windows.

Main features of Graphical User Interface OS

Main features of Graphical User Interface OS:

1. In the graphical user interface a visual environment is present.
2. The multi-tasking nature of modern computers means that there can be several windows open at the same time.
3. Windows can be resized, moved etc.
4. Applications run in windows.
5. It is user-friendly.
6. It is more attractive for non-technical people.
7. It does not require memorization of command.
8. A GUI will require a lot more system resources because of each of the elements that need to be loaded such as icons, fonts, etc.

Main features of Text/ Command line interface OS

Main features of Text/ Command line interface OS:

1. The user gives instruction to the operating system by typing in the commands at a command prompt.
2. It requires the memorization and familiarity to operate a command line interface by user.
3. Text-based systems run faster.
4. Text-based applications use memory more efficiently.
5. Command line interfaces often provide the user more control on the software then a graphical user interface, by taking all the details of a command as parameters and/ or by redirecting the outputs between commands.

Classify operating system based on command

Classify operating system based on command:

Every computer that is to be operated by an individual requires a user interface. The user interface is a component that interacts with the computer user directly, allowing them to control and user programs.

Based on command, the operating system can be classified into two categories, as:

1. Text/ CLI based OS.
2. Graphical User Interface (GUI) based operating system.

Operating system & Its Function

Operating system: 

Operating system (OS) is a set of software which controls the execution of computer programs and which provides scheduling, resource allocation, debugging and related service. It works as a bridge between the user and the machine.

Figure: OS

Function of Operating System: 

1. It makes the computer active and use-able.
2. It manages the processor.
3. It co-ordinates different machine and software.
4. It manages memory.
5. It allocates resources.
6. It assigns priority.
7. It controls input and output devices.
8. About all, it creates working environment.