Operating system

Hierarchy of computer software

Operating System
a collection of programs which control the resources of a computer system
written in low-level languages (i.e. machine-dependent)
an interface between the users and the hardware
when the computer is on, OS will first load into the main memory

What is OS?
Operating System is a software, which makes a computer to actually work.
It is the software the enables all the programs we use.
The OS organizes and controls the hardware.
Examples: Windows, Linux, Unix and Mac OS, etc.,

Operating
System
Device configuration
Controls peripheral devices connected to the computer
File management
Transfers files between main memory and secondary storage, manages file folders, allocates the secondary storage space, and provides file protection and recovery
Memory management
Allocates the use of random access memory (RAM) to requesting processes
Interface platform
Allows the computer to run other applications
Basic functions of the operating system

Other function of Operating System
best use of the computer resources
provide a background for user’s programs to execute
display and deal with errors when it happens
control the selection and operation of the peripherals
act as a communication link between users
system protection

Common Operating Systems and Their Differences
Network Operating System
UNIX / Linux / MS Windows2000 Server
Desktop Operating System
MS Windows 9X/Me / Mac OS / DOS
Mobile Operating System
Palm OS and Pocket PC

Examples
Common operating systems
WINDOW
used in IBM compatible microcomputers (используется в IBM совместимых микрокомпьютерах)
UNIX
multi-user, multi-tasking OS used in minicomputers and microcomputers

DOS interface

GUI

Different Types of Operating System

Types of OS:
Operating System can also be classified as
Single User Systems
Multi User Systems

Single User Systems:
Provides a platform for only one user at a time.
They are popularly associated with Desktop operating system which run on standalone systems where no user accounts are required (настольные операционные системы, которые работают на автономных системах, в которых нет учетных записей пользователей).
Example: DOS

Multi-User Systems:
Provides regulated access for a number of users by maintaining a database of known users (Обеспечивает регулируемый доступ для нескольких пользователей, поддерживая базу данных известных пользователей).
Refers to computer systems that support two or more simultaneous users (Относится к компьютерным системам, которые поддерживают два или более пользователей одновременно).
Another term for multi-user is time sharing.
Example: Unix

Good Operating System
efficient
time spent to execute its programs should be short
small in size
memory occupied should be as small as possible
reliable (надежный)

Type of Operating System
Batch processing
Real time processing
Time sharing processing

Batch processing
Jobs, together with input data, are fed into the system in a batch (входные данные, подаются в систему в пакетном режиме).
The jobs are run one after another.
No job can be started until previous job is completed

Real time processing
immediate response is needed (немедленного реагирования).
For example
anti-missile defense system (в противоракетной обороне)
airplane landing control system (система управления посадки самолета)