Operating Systems 1 Flashcards
Operating System
An operating system is software that runs on the computer which manages how the computer operates. The operating system provides useful functionality.
The Kernel
The kernel is the first part of the operating system code to be loaded, and has complete control over the computer.
It is responsible for controlling access to the computer’s most sensitive information and functionality, and is loaded into a protected region of memory to prevent accidental or malicious corruption by other programs.
The kernel is responsible for the loading of new programs, handling input and output between peripherals, and managing access to the hardware’s shared resources, such as the RAM and hard drive.
Processes
A process is created on a computer when a program is requested to be loaded. The computer will load the code in the program, such as Google’s Chrome browser, and will create a process which contains all of the necessary information for execution by the processor.
Interrupts
An interrupt is a signal that is sent to the CPU, which alerts the CPU to a task requiring its immediate attention. An interrupt will halt the CPU and cause it to begin executing the corresponding interrupt handler.
Hardware Interrupts
A hardware interrupt is generated by some sort of hardware either inside or outside of the computer. This includes a keyboard or mouse, which will send interrupts when new input is available.
The interrupt handler will then be executed, and the window which is currently in focus will receive the keyboard input via the operating system.
Software Interrupts
A software interrupt is an interrupt which is generated by software. A program may want to generate an interrupt when it wants to open a file for example.
The program has to do this because the act of opening a file is a privileged operation, and as such the kernel has to be consulted before the operation takes place.
Software interrupts act as an interface between the kernel and the program.
In short, the program can use a specific interrupt to ask the kernel to perform an operation on its behalf.
Bootloader
The bootloader is a program which is loaded by the BIOS when a computer is first turned on and is responsible for loading the operating system.
A bootloader is necessary due to the complexity that would be involved in creating a BIOS capable of loading hundreds of different operating systems.
Due to this, the bootloader is usually installed at the same time as the operating system and is loaded from a known place on the hard drive by the BIOS.
The BIOS (‘Basic Input Output System’)
A program stored on the motherboard of your computer. When the computer is first turned on, it is the first program that is loaded and prepares, or initialises, the hardware ready to load the bootloader.
Nowadays, modern computers almost exclusively use UEFI (Unified Extensible Firmware Interface).
UEFI is the successor to BIOS; however, the term BIOS is commonly used as an umbrella term for both due to the similarities between them. UEFI achieves the same functionality as BIOS, in a more versatile and secure manner.
