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It is essential to pay attention to the operating system, which is a key item in the software classification of the software needed to recover a computer.
Introduction to operating systems
This is the most important software needed to run a computer. An operating system controls and maintains all the processes on the computer, providing an interface to maintain the connection between the user and the hardware.
As soon as a computer is turned on, the BIOS program controls the overall performance of the computer by staying in the main memory until the operating system shuts down.
Booting the computer
Booting is the process by which a computer is powered on until it becomes usable by the user.
පසු After powering the computer, it restarts and confirms the power supply.
Then the Bootstrap loader program in ROM is activated and the BIOS program is executed.
This checks if the computer's input and output devices are working properly. If it does not work properly, it will make a beep. This is called power on self test (POST test).
Bo The boot sector then redirects to the CMOS memory and identifies the location where the operating system should be located (often the operating system is on the hard disk and may be in other storage when formatted, such as a CD).
Master The master boot record at that location contains a set of 512 byte instructions and executes it.
It copies the operating system to the main memory and then gives control of the computer to the operating system and the user.
Evolution of operating systems.
Operating systems evolved and evolved under several conditions, from the operating system currently used in computers.
Lack of an operating system.
Original computers did not use an operating system. The tasks to be performed here are executed by the computer programmer himself by inserting them into the main memory.
characteristics
o Utilization of the processor utilization (making maximum use of the processor capability).
o Processor time wasted during input and output operations, ie the processor does not work.
o Linear layout i.e. one task after another.
o Programs are accessed directly from the computer
Simple Simple batch system
In the past, this operating system was introduced to automate some of the tasks performed by the user himself. In this case, the programs to be executed were written on a magnetic tape and given to the computer one at a time, and the output of the activated program was written on a printer or other magnetic tape and the other program was inserted into memory.
characteristics
o Implementing only one program at a time.
o No special interface to connect to a user.
o Processor laziness during input and output operations.
o Increased ability to respond.
o There is no direct access to the program.
o Use of programs written on a magnetic tape.
Mult Multi programmed batch system
This was introduced on third-generation computers to avoid wasting processor time. Here the main memory is divided into sections to send several programs to one memory at a time. (Dividend)
When one program has an input or output function, the processor executes the other program that is stored in memory.
Sharing Time sharing operating system
This allows the processor time to be directed to multiple programs at the same time, making the most of the processor utility. Here the context switch is used to store several programs in memory and execute each program at the same time. This did not waste processor time. Most of the computers we use today use this time sharing method.
Some of the key functions of an operating system.
Resource management.
Provide an interface.
Operational management.
Protect the computer.
Providing an interface. (Interface)
This allows the user to use the computer while managing software and hardware. The interface has several modes.
1. Command line interface
Here the required data and instructions on an inductor on the computer screen should be encoded according to the correct operating rules. There should be an experienced person with special knowledge to use these interfaces. Code must be remembered. These interfaces are used in operating systems such as MS doc, unix, and linux.
