what is an operating system (basic definition)
- is software that manages computer hardware and software resources
- all computer programs (other that basic firmware systems) require an os to function
examples of an os
- windows
- linux
- IOS
- android
what us an operating system (its function)
- it provides a layer of software services which are used to interact with the hardware (it acts as a layer between the software and user an the hardware)
- os can be extremely large and so no all of the os will be loaded into the main memory
- the kernel is loaded into RAM when the computer boots up and this is responsible for managing processes, hardware and other important low level tasks
functions of os: process management
ensuring that different processes/programs can be run and in a multi-tasking os appearing to run simultaneously using scheduling
(makes use of interrupt handling)
functions of os: input/output management
communicating with devices such as keyboards, mice, printers, monitors etc
(makes use of interrupt handling)
functions of os: backing store management
ensuring data can be read/written to disk drives, maintaining a hierarchical file system etc
(makes use of interrupt handling)
functions of os: memory management
ensuring that programs and data can share memory and are stored correctly without interfering with each other
functions of os: human computer interface
to display information to the user and accept input
functions of os: utilities
software that comes with the os to help with the running of the computer, eg. file management, backup, virus scanning etc
functions of os: security
os will typically have security built-in such as login/password, encryption, file access rights etc
functions of the os that are carried out by the kernel
- interrupt handling
- input/output management
- scheduling
- memory management
what do hardware drivers do
perform the translation between the generic os instructions and the specify binary control signals that the hardware understands
(if you buy a printer, mouse, keyboard etc and there isn’t a compatible driver available for it for the os you are using, then it wont work)
what is the kernel
the central component of an os that communicates with hardware and software
describe the purpose of an os in a personal computer
- provides a user interface, typically WIMP
- provides an interface to peripherals devices such as keyboards, mouses and printer
- running software programs, by loading program code and data into RAM then activating the CPU to execute the program
- allowing multiple programs to be active at the same time by sharing processor time
- providing an interface for local or wide area networking
- providing the device drivers to allow new peripherals to be installed
- controlling the storage of files in secondary storage, and displaying a catalogue of programs and data files
- providing security to prevent unauthorised access
- allowing multiple users to have personal secure access through a password system
- responding to system errors in a way which minimises data loss
managing backing store
- storage devices are managed by the is which will be able to read and write files and folders/directories and maintain a hierarchal structure, file access rights
- information about files is stored in an index known as file allocation table (fat), which stores the locations of all files on the drive together with meta data about file including file name, creation/ modify date, size, file access rights
