Chapter 3 Computer Science

Pregunta	Respuesta
What is software?	Programs that we run on our computers.
What are dedicated systems?	Dedicated systems have software installed on a chip of some sort. Such as a washing machine which only controls the functions of a washing machine.
Laptops, tablets, computers and phones are all what?	Multi-purpose as they run different programs according to the wishes of the user.
4 secondary storage mediums	A hard disk A memory stick An SD card An optical disk (CD or DVD)
Where are the programs loaded?	RAM
What does system software do?	It controls the hardware.
What does application software do?	It handles the real-world jobs that users want to do.
What does utility software do?	It has limited functionality and is used to maintain computer systems.
How is software usually produced?	Using a programming language.
How is some software produced?	By an automatic software generator.
Without system software, what would application programmers have to do?	Take into account the precise movement of data between locations.
System software looks after movement of data so that the programmers can?	Tackle algorithms to solve real-world problems that the user has.
What does system software act as?	An intermediary between the application and the hardware.
What does system software do?	It hides the complexities of the hardware from the user and the application programmer. It allows the user to operate the computer without having to write programs.
What is the main part of system software?	The operating system.
What is the operating system?	It is a set of programs that controls the hardware and lets user and applications work with the computer.
What is a kernel?	A kernel is the part of the operating system that actually makes the hardware do things.
What must an operating system do?	Provide a way for a user to control and interact with the computer.
What is the user interface?	It is a boundary between the human user and the machine.
What does the user interface do?	Lets the user give commands. Ask questions. Displays a response.
New ways of what are being developed?	Of operating systems doing things differently.
What is the command-line interface?	It is an interface which requires the user to write commands.
How does the computer understand these commands?.	It is translated by a command interpreter into signals that the computer can understand.
What is the command 'ls' and what does it do?	List - Shows files in the current directory. Data files, executables and directories are colour coded in some systems.
What is the command 'cal' and what does it do?	Calendar - shows the days of the current month (the command can be modified to show any month or any year).
What is the command 'w' and what does it do?	Who - Shows who is logged in and what they are doing.
What is the command 'pwd' and what does it do?	Present working directory - shows the full location of your current directory.
With commands, what can you do?	Completely control a computer system.
What are shell scripts?	Shell scripts are commands grouped together to carry out maintenance jobs automatically.
What is a shell needed for?	So that a user can communicate with the kernel.
What is a GUI?	Graphical User Interface
What does GUI use?	Images (known as icons) which represents resources, files, programs and actions.
How does a user make something happen when using a GUI?	By clicking on areas of the screen or touches them or pinches them.
Why are GUIs a useful way to interact with a computer?	They are intuitive. No special training is required. Keyboard use is limited - useful where there is a small or virtual keyboard. No commands need to be learned.
Where does this interface sit?	On top of the operating system kernel.
What does the GUI allow easy access to?	Selecting software. Selecting files. Sending messages. Controlling sound volume. Connecting to WiFi. Deleting files. Moving files. Checking battery state. Updating software. Installing new software.
Why is speech input difficult to get right?	Accent. Speed of talking. Dialect used. Clarity of diction.
What is speech input useful for?	Selecting options on telephone menus. Giving commands to a computer. Dictating text.
Why do subtitles on television programs sometimes have errors?	They use speech recognition software and the difficulty causes mistakes.
What do operating systems have to make sure of?	Memory is used efficiently. Important data is not written during the running of a program.
What is memory divided into?	Pages.
What is a program called when it is being executed?	A process.
When a job needs to be done, what does the operating system do?	Load the process on a vacant page and keeps track of it so it isn't overwritten by other processes.
What is virtual memory?	A technique which involves swapping jobs in and out of memory.
What does virtual memory use?	It uses secondary storage to hold parts of the program which is not curredntly needed.
Why is virtual memory used?	There is not enough space in meory to hold all the jobs, so it is split into modules although it is slower than main memory/
How are modules used?	They are stored separately on secondary storage. When a module is needed, it is loaded into memory (swapped in) and run as a process. When a different module is needed, it can overwrite an unused module.
What must an operating system do?	Keep track f which pages are vacant and which processes are currently swapped in or out.
What is a file?	A file is named store of data on a secondary storage medium.
What can files be?	Data files - word processed document or a dtabase program files - operating system components or applications Configuration data - parts of the Windows registry
What happens when you save a file?	The operating system looks up where there is free space on the medium. It writes the data and makes a record of where it is located. Next time you need it, the operation system looks up its location, finds it and retireves it.
What is secondary storage is divided into?	Segments.
What are file usually split into to?	Blocks across many segments.
Each block contains what information?	Information on the location of the next block, so the operating system can follow pointers to recover the whole file.
What is defragmentation?	A process that is used to tidy up the disk or other medium so that parts of a file can be moved to be stored next to each other.

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