Operating Systems Flashcards
Operating system
to allocate the shared system resources to the executing programs
a collection of program which makes it easier for us to use a computer
a simpler abstraction of the underlying hardware (hides the complexity of hardware)
Hardware
basic computing resources, cpu etc
Operating system
controls and coordinates use of hardware amongst application and uses
Application programs
ways in which the system resources are used to solve computing problems, compilers, text editors, email clients, webs browsers, games
Users
people, machines and other computers
Uniprogramming
Ability to only conduct one program at a time
Multi-programming
Executing multiple programs on the same CPU giving the user the impression that these programs are running at the same time but in reality they are running one after the other
There must be enough memory to hold the OS (resident monitor) and one user program
When one job needs to wait for the I/O the processor can switch to the other job which is likely not waiting for the IO
Time sharing system
Principle objective is to minimise response time
Bootstrap program
Small piece of software stored in the memory area which kicks in and loads the system when you press the power button to turn your laptop on
ROM
Read-only Memory
EEPROM
Erasable Programmable Read-Only Memory
Firmware
Create some processes
System processes
Actives tasks or instances of programs, often initiated or interacted with by users
System daemons
Processes in the background, running at all times regarding of whether the user is executing something or not
Registers
A type of memory, very small but very fast
Smallest one on the cpu
Main memory
Much larger, relatively slow, every system needs to have it
CPU can load instructions only from memory meaning any programs to run must be stored there
Secondary storage
Goes away when machine is switched off, magnetic disks, optical disks, tapes (external devices)
Cache memory
Data that has been used a lot is cashed into a faster storage system
If the CPU is looking for information, cache is first checked
Storage Structure
- Memory is an array of bytes, each byte has its own address
Memory interaction via load/store instructions
Load Instructions
Moves byte from main memory to an internal register within the CPU
Store memory
Writing of a byte from CPU register to main memory
Large portion of OS code dedicated to managing I/O devices
Without having any I/O devices you won’t be able to program or give anything from the outside world to the system and vice versa
Local Buffer Storage
Temporary memory area within a system or device that is used to store data temporarily while it is being transferred between components, processed or waiting to be used.
Device Driver
Typically downloaded
Whenever a user program wants to issue a command to a device, this will send the command to the OS.
The OS will give the command to the DD who will transfer this to the disk controller.
