1.5.1 Operating systems

What is an operating system?

Software that manages the computer’s hardware and provides a user interface

What are the functions of an OS?

User interface, memory management & multitasking, peripheral management & drivers, user management, file management

What do we need user interfaces for and what would happen if they didn’t exist?

They allow humans to interact with the computer and we’d need to write in binary to interact instead

What are the different user interfaces?

Graphical, command line, menu driven, natural language

What type of user interface is Windows?

A WIMP user interface

What is a WIMP interface?

Windows, Icons, Menus, Pointers

How do users interact with icons in a WIMP interface?

By clicking on icons using a pointer or cursor

Why do icons reduce the need for typing?

Icons represent functions so users can click instead of typing long instructions

What does right clicking do in a WIMP interface?

It opens a context sensitive menu

What is a command line interface?

A software you use to interact with your operating system by typing text commands using your keyboard

What are features of command line interfaces?

User commands are typed in as text, no graphics, quicker & more flexible for expert uses, uses less space on the disk and in RAM

What is a menu-driven interface?

A type of user interface where users interact with a program or system through a series of menus

What are the features of menu driven interfaces?

Easy to use as the user doesn’t have to remember sets of commands, user friendly as you can often guess your way around the options

What are natural language interfaces?

They allow the user to interact using written or spoken ‘human’ commands instead of computer language

What are features of natural language interfaces?

Improves day-to-day functionality, convenient for users

What must happen to programs before they can be used by the CPU?

They must be copied from secondary storage into RAM

What else is copied into RAM besides the program itself?

All data used by the program

What does the operating system keep track of in RAM?

The location of each program and its data

Why must the OS not overwrite existing programs in RAM?

To allow multi-tasking and prevent programs from interfering with each other

What is RAM used for?

Storing all programs and data currently in use

What does the OS do when programs are closed?

It keeps track of the free spaces in RAM where new programs can be loaded

What is memory fragmentation?

When consecutive memory locations contain a mixture of instructions, data from different programs or empty gaps

What happens when RAM is full?

The OS uses part of the secondary storage as virtual memory

What is multitasking?

Using a computer to perform several tasks at the same time

How does the CPU handle multiple tasks at the same time?

Each task takes turns using processor time to execute instructions

What manages how processes share the processor?

The operating system

What is a peripheral?

Any hardware device that is not part of the CPU

What are examples of peripherals?

Mouse, keyboard, printer, camera, RAM, secondary storage

What are the OS’s responsibilities when managing peripherals?

Receiving input, sending output, copying files from disk to RAM, and copying data back to secondary storage

What is a device driver?

A small program that acts as an interface between the computer and a peripheral

What is the purpose of a device driver?

To allow the OS to communicate with and control a peripheral device

How does each device communicate with the OS?

Through its own specific device driver

What happens if the wrong driver is installed for a device?

The computer will not know how to communicate with the peripheral

What is buffering?

A technique to deal with the differing speeds that data is received and the rate in which the device functions

Why is buffering needed?

Computers send data faster than some devices can process it

What is a data buffer?

An area of memory (RAM) in the computer or the peripheral used to temporarily store data

Where can a buffer be located?

In the computer’s RAM (managed by the OS) or in the peripheral’s own memory

What does the OS do for user management?

It allocates user accounts and manages logins and passwords

What can the OS include for extra protection?

Password protection on individual files

What does the OS control regarding users?

Access rights

Why are access rights important on a shared computer?

Each user should only be able to see their own files

Who has different levels of access rights?

Regular users and system administrators

What might some users be allowed to do with files?

Read them but not edit them

What type of device is a hard disk?

A storage peripheral

What does the OS do when managing files on the disk?

It manages where files are written on the disk

Why does the OS keep track of where files are stored?

So they can be found and retrieved later

What does the OS ensure when saving files?

That no files overwrites another file

What does a file extension tell the OS?

Which application should be used to open the file

How does the OS help users organise files?

By showing files in a logical structure of folders

What file operations does the OS allow users to perform?

Create, rename, delete and copy files and folders

How does the OS simplify file management for users?

It hides the hardware complexity so users don’t need to know where on the disk a file is physically saved

What does the user need to do when saving a file?

Click ‘save’ and the OS will handle everything else