Software Concepts (unable to edit because my pro subscription ran out :l) Flashcards
What are the different types of multi-user operating systems?
- Single Processor System
- Multiple Processor System
- Networked Systems
What are the two types of Operating Systems?
- Single-User Operating systems
- Multi-User Operating Systems
How many users can use a Single user operating system?
- Only one user to make use of a PC at any given time.
- They are common on personal computers.
- Windows 7
- Apple Mac OS X
What is a Multi-user operating system used for?
- Originally used on mainframes.
- Used for high-volume data processing tasks.
- Nowadays they are often used on networked systems.
Explain what a Single Processor Multi-User System is.
- Only a single processor or CPU.
- CPU is shared between users by dividing the CPU time into time-slices. Allocating one of these to each user in turn
- The time-slices are very short giving each user the impression that their programs are running continuously
What is a Networked System
- Single user PCs connected together to form a Local Area Network (LAN)
- Each PC has a Network Interface Card (NIC)
- Connected by means of copper, wireless or fibre cables
- Allow users to share files and resources such as a printer or an Internet connection.
- Include Windows NT, Windows 2000/2003/2008 Server and Unix/Linux
What is a Real Time System
- They monitor external events and react instantaneously, hence the expression “real time”.
- Used for direct control over electromechanical equipment
- Such as:
- Industrial robots
- Factory processes
- Power stations
- Airplanes, trains and cars.
What are the five layers of the Operating System
Listed from center to outerlayer
- Kernel
- Memory Management
- Input / Output
- File Management System
- User Interface
What is the User Interface Layer of the operating system.
The software layer which allows the user to interact directly with the operating system.
What are the two distinct types of User Interface:
- The text-based Command Line Interface (CLI)
- The icon-based Graphical User Interface (GUI)
What is the objective of the User Interface
- The principal objective of a user interface is to allow the user to interact with the computer.
What input and output facilitys does the user interface need?
- Input facility
- eg: Via a keyboard, mouse or joystick.
- Output facility
- eg: A display or printer.
What does the User Interface layer of the operating system allow the user to do?
Allows the User to:
- load and run programs
- controls the interaction between programs and the user.
- modify system settings
- control system functions
- request information
What does a parameter do in the command line interface?
A parameter provides additional information which the CLI requires in order to carry out its function.
eg: the MS-DOS command dir displays a list of the files in a directory or folder:
What does a switch do in the Command Line Interface
- A switch is used to modify the way a command executes or how it displays its output.
- MS-DOS switches are preceded by the forward slash character, “/” and are placed at the end of the command line, after all parameters, eg:
- C:> dir windows /p
- Lists the files in the windows folder, but if there are too many to fit on the screen it pauses its output until a key is pressed.
- C:> dir windows /p
What replaces parameters and switches in the graphical user interface(GUI) ?
- Parameters and switches are replaced by dialogue boxes.
What is a check box in the Graphical User Interface.
Check Boxes:
- Similar to switches.
- When the box is checked, the switch is on, when unchecked the switch is off.
What are radio buttons in the Graphical User Interface
- Radio buttons provide a set of options, only one of which can be “on” at any time.
What are list boxes in the Graphical User Interface?
List boxes:
- Lists of parameters, from which one can be selected.
What are edit boxes in the Graphical User Interface?
Edit boxes:
- boxes that allow parameters to be typed in.
What are buttons in the Graphical User Interface?
Buttons:
- Used to select further options or dialogue boxes
What is the File Managment System
- It is the layer of system software responsible for organising and managing the storage of data on permanent media.
What is a File Extension
- Helps you identify the type of document.
- Allows your computer to run the correct program automatically when you double-click on the file name.
- Computer files have specific characteristics depending on the program that was used to create them
- File extensions are a way of labelling the names of files so you and your computer can keep track of what they contain.
What is File Locking
- When a program asks the operating system for access to a file, this is only granted if the file is not already in use.
- If the file is already open, the program must wait until it is free.
What is the Input/Output layer of the operating system?
- Controls all physical communication with external devices
- disk drives
- keyboard
- printers
- displays
- Processes in the I/O layer are usually activated by means of interrupts.
What is Character I/O
- Character I/O
- Where the data is in the form of single numbers or characters (eg: keys pressed on a keyboard)
What is Block I/O
- Block I/O
- Where larger blocks of data are to be transferred at the same time (eg: reading or writing a block from disk).
How is data transfered using Character I/O
- Small amounts of data, normally a single byte, are transferred on each interrupt
- Total amount of data to be transferred may be large, but it is broken into small quantities
- The commonest character-mode devices are the keyboard, mouse, joysticks, communications ports and printers.
How is data transfered using Block I/O
- Large amounts of data (eg: a 2,048 byte disk block) need to be read into or written back out from memory.
- Could be carried out in the same way as character I/O, by reading or writing the data one byte at a time, however this would be a waste of processor time.
- Instead, the interrupting device carries out the transfer of the data into memory by itself
- Known as Direct Memory Access (DMA) and is used wherever large amounts of data need to be transferred between a device and contiguous memory locations as a block
- All I/O process needs to do is tell the device where in memory to start writing the data and when to start
What is the Memory Managment layer of the operating system responsible for
- Responsible for
- Sharing the physical memory of the computer between processes.
- Handling programs which require more memory than physically available.
- Responsible for ensuring that the memory allocated to any program is protected against access by other programs.
- What is virtual memory?
When a program requires memory it is allocated a number of pages
This can happen both when it is initially loaded or if it needs additional memory at a later stage
If all the available pages are already in use the memory management system looks for a page that it can reclaim
