An Operating System is a resource manager which allocates and manages various resources like processes,main memory, I/O devices and information on secondary storage.
What Is an Operating System (OS) ?
An Operating System is a program that manages application programs and work as an interpreting medium between the computer user and computer hardware.
The purpose of Operating System is to provide an environment in which a user can execute all types of programs in a convenient manner.
Types Of Operating System :-
- Simple Batch Operating Systems
- Real-Time Operating Systems
- Time-Sharing Operating Systems
- Distributed Operating Systems
- Network Operating Systems
Simple Batch Operating Systems
In the Earliest days, digital computers usually run from a console. I/O devices consist of Card Reader, Tape Drives, and Line Printers. Direct interaction between user and jobs not exist.
User creates a job and submit it to the operator, who would execute the job on the computer system. It takes more time (minutes, hours or sometimes days) to execute a particular job.
The OS was very simple and its major task was to transfer control from one to another. the OS was resident in memory. To fasten the processing, jobs with the same needs were batched together for execution, thus Batch OS came into existence.
Difficulties faced in Batch Operating Systems are :-
- It lacks interaction between users and jobs.
- Processing is slow due to the slow functioning of I/O devices (seconds or minutes), CPU operates very fast (nanoseconds).
- It lacks Priority-based execution.
Spooling is introduced to overcome these problems. Instead of reading from slow input devices, the input is first to read into the disk when the job is processed or executed. The input is read directly from the disk.
When a job is executed for printing , the output is written into a buffer on the disk and actually printed later. This form of processing is known as Spooling.
Real-Time Operating Systems :
Real-Time Operating Systems are specially designed to respond event that happens in current (real) time. It has well defined, fixed time limits.
The time taken by the system to respond over an input and display the required information is called as Response Time.
Processing must be done within the definite time limits or else the system will fail. This system is very useful in implementing systems, such as airline reservations system.
Time-Sharing Operating Systems :
Time-sharing OS is a popular type of multi programmed, multi-user system. Time sharing OS has good terminal Response Time. Time Sharing systems generally attempt to share equitable sharing of common resources.
For example, when the OS is loaded, users with more demanding processing requirements are made to wait for long duration.
- In Time-Sharing systems Memory Management provides isolation and protection of stored programs.
- I/O in Time-Sharing systems must be complicated enough to cope with multiple users and devices.
Device Management
OS manages all I/O components connected to the computer system and internal devices. OS has the Device Drivers of some components to control them and some devices are controlled through external device driver installations.
Distributed Operating Systems :
In Distributed Operating System all the Computations are distributed among several processes. Distributed Systems also referred to as loosely coupled systems because the processor does not share the memory or a clock.
The processes communicate with one another through various communication lines, such as high-speed buses (system buses) or telephone lines.
Functions of Operating System :-
- Device Management
- Process Management
- Memory Management
- File Management
- I/O Management
- Security and Protection
- Control Performance Of System
- Job Order Management
Detects Errors
- Operating System detects I/O errors.
- It Detects Processing errors, etc.