Main features of an operating system

Вне зависимости операционной системы все они выполняют эти задачи.

 

Process Manager

The OS must allocate (выделять) resources to processes, enable (разрешать, давать возможность) processes to share and exchange information, protect the resources of each process from other processes and enable synchronisation among processes.

To meet these requirements, the OS must maintain a data structure for each process, which describes the state and resource ownership of that process, and enables the OS to exert control over each process.

 

Memory manager

The memory management function keeps track of the status of each memory location, either allocated or free.

Determines how memory is allocated among competing processes, deciding which gets memory, when they receive it, and how much they are allowed.

Determines which memory locations will be assigned when memory is allocated,

Tracks when memory is freed or unallocated and updates the status.

 

File manager

A file manager or file browser is a computer program that provides a user interface to manage files and folders.

Folders and files may be displayed in a hierarchical tree based on their directory structure.

The most common operations performed on files or groups of files include creating, opening (e.g. viewing, playing, editing or printing), renaming, moving or copying, deleting and searching for files, as well as modifying file attributes, properties and file permissions.

 

Device manager

The device manager is responsible for detecting and managing devices, performing power management, and exposing devices to user space.

Device drivers allow user applications to communicate with a system's devices.

They provide a high-level abstraction of the hardware to user applications while handling the low-level device-specific I/O and interrupts.

 

Network Manager

The network manager manages the relationship between the operating system and the network(s) that it is connected to.

This means that the user can be unaware of issues like connectivity, and network speed.

Коммуникация с другими устройствами.?

DATA BASE

File processing system

In past many organisation stored data in files on tap or disk.

Data was managed using file-processing system.

Each organisation has its own set of files.

Record in one file are not related to the record in other file.

No relation between files.

Disadvantages:

Data redundancy (избыток). Информация в разных файлах повторяет себя

Inconsistency - несогласованность, противоречивость). Разные файлы могут иметь разную информацию, хотя должны бы одну

Data isolation - слишком много времени для того чтобы найти полную информацию, когда разная информация об одном и том же находится разных файлах.

Integrity (целостность) problem. Например, имя написано цифрами.

Security issue

 

A database is a repository (хранилищее) of data, designed to support efficient data storage, retrieval (пооиск) and maintenance.

Multiple types of databases exist to suit various industry requirements.

A database may be specialised to store:

- Binary files

- Documents

- Images

- Videos

- And many others

 

Database Model

Relational database

- Tabular format

Hierarchical database

- Tree structure

Network database

-  Graphs representing relationships between objects

 

Types of Database System

 Centralised database

одна большая база и все компьютеры подключены к ней. она централизованная. есть домен.

Client/server database

 

Distributed database

разделяют данные - если на одном сервере информация исчезнет из-за поломки, то на других базах она должна остаться.

 

2019. 5.8

Tech-enabled company - используют технологии, но е создают их.

Usa: faang

F facebook

A amazon

A apple

N netflix

G google

China bat + huawei

B Baidu поисковик, сродни гуглу

A Alibaba мессенджер и доставка?

T wee chat мессенджер и оплата

+huawei (заблочен в юс потому что они имеют доступ к информации на продуктах хуавей + они думают, что файлы были украдены для создания технологий, однако нет доказательств этому)

Korea

Kakao, naver, coupang, gmarket, tmon

samsung, lg

 

 

2019. 5. 2 2 Internet and web

Isp internet servis provider