Lectures 1-5 Flashcards
What is a DOS?
A disk operating system
How do DOS’s work?
By using command line interfaces
What are the purposes of a GUI?
- Execute programs
- File management
- Tools to configure and interact with OS which may be tightly linked
What is the communication protocol used between the operating system and the window manager called?
X11
What model does the X11 protocol use?
It uses a client-server model
Why does the X11 protocol create minimal network traffic?
As it only has 4 packet types:
- Request
- Reply
- Event
- Error
How has the role of the X11 protocol changed?
It has gone from originally drawing the display to now sending commands to the OS’s window managers
What is an interrupt?
When an input happens (like a mouse click) it is passed directly to the processor which stops what it is doing to process this new command
What is polling?
When the computer periodically checks for inputs. However this means that an input may be missed when the computer is listening for another.
What are the OS’s services to the user?
- It creates an illusion of having direct access to the
hardware - It creates an illusion of being the only user (on a
multiple user system) - Multi Tasking
What are the OS’s services to programs
- It will allow the program to use OS facilities if
necessary such as the camera or microphone - Give it the illusion of it being the only program running on the system at the time
What are the pros of using a CLI over a GUI program?
- It provides a powerful way of interacting with the OS
- Often less frustrating for repetitive tasks
- Can combine multiple simple commands for complex tasks
- Great for controlling remote systems like servers
What are the cons of using a CLI over a GUI program?
- Initially more difficult than a GUI progam
- Help is not as readily available
- Not as many safety belts as there are with a GUI
program (Will not say ‘are you sure’)
What does a shell do?
It provides a coating around the OS (Provides an interface)
What are some shell features/utilities?
- File and directory management
- Ability to use internal and external commands
- Control of programs and processes
What do file permissions do?
They allow enhanced security in a multi user environment. These can apply to bot files and their directories
What are the different types of file links?
Hard links and symbolic links
What are the properties of hard links?
- Gives multiple names for the same file
- Restricted to the same filesystem
- Cannot link directories like this, only files
What are the properties of symbolic links?
- Redirect using the path name to another file (like
saying ‘The file you want isnt here, it’s over there’) - Can link to directories, or across filesystems
How are links created?
Using the ‘ln’ or ‘ln -s’ command, then the name of the existing file and the new name afterwards
How can output be redirected to a file rather than to a shell?
By using ‘>’ and ‘»’ (‘>’ is overwrite, ‘»’ is append) after a command and before the name of a file
How can input be taken from a file rather than from a user’s input
By using
How can the output of one command be given as the input to another command
By using a pipe symbol (‘ | ‘)
What is the data throughput rate?
The number of bytes (or bits) that can go across the bus in one second
