Computer Science

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Operating systems:

Software can be split into two separate categories:

system software

Application software

System software can then be split into four other categories:

Operating systems (Linux, iOS, windows)

Utility programs (file explorer, anti-virus)

Library programs (.dil files in Windows)

Translators (The software that translates your programs into machine code)

Application software:

Application software is split into four different subcategories:

Off the shelf software, (commercially sold, regular updates and hot fixes)

custom written software, (can't have regular updates, custom made for businesses)

proprietary software

open source software. (code can be edited by customers)

User Interface:

Operating system functions:

Provides a user interface (without a user interface we would have to communicate in binary)

Memory Management

Peripheral Management

Multi-tasking

Security

Types of user interfaces:

GUI: Graphical User Interface (WIMP: Windows,Icons, Menus and Pointers)

Menu-driven interface

CLI: command-line interface (Just text, like Windows command prompt)

Voice activated

Real-time (sensors detect inputs, actuators output actions)

WIMP interfaces:

User can click on icons using a pointer or cursor

Icons represent main functions rather than having to type instructions.

Right-click to get context-sensitive menus

DIfferent shaped pointers for different uses

WIMP interfaces also allow the user to see how things will look when they are printed. This is called WYSIWYG (What You See Is What You Get)

Before WIMP interfaces the version on the screen wouldn't be the same as the printed version.

WIMP interfaces are more complex so they take up more disk space and RAM.

Simple devices with small amounts of storage and RAM are unlikely to have a WIMP interface.

Menu-driven interfaces are less commonly used but still prevalent in some areas.

Command line interfaces:

All user commands must be typed in text.

There is no graphics available in CLI

Quicker for experts users who know the commands but slower for beginners who need to learn the commands.

Takes less space on the disk and in RAM.

Before WIMP there used to be a lot of text-based adventure games. You'd have to work out what commands to type to get where you wanted to go.

Functions of the operating system:

Examples of operating systems: Android OS, OS X (Mac), iOS (iPhone/iPad and Linux)

Definition: "Software that manages a computer's hardware and provides a user interface"

Memory management:

To run a program, the computer must copy the program from storage into the main memory. Data used by the program is copied into the main memory. The operating system keeps a record of where each program and its data is located. It must not overwrite existing programs.