general theory Flashcards
operating system
a collection of suite programs that manages and controls the computer. It keeps the details of how this is done hidden from the user
the main functions performed by an operating system (4)
- file management
- process management
- hardware management
- user interface management
common operating systems (5)
- Microsoft Windows
- macOS
- Linux
- Android
- iOS
how is data stored in files within folders within drives
by creating a virtual file structure of the physical components. It has a hierarchal structure starting with the root directory, a bit like an upside down tree
the file system assigns meta data to each file including:
- date created
- date modified
- last date accessed
- last backup
- file creator user ID
- access permissions
- file size
functions users can perform on files (6)
- create
- name/rename
- save
- copy
- move
- delete
multiprograming
enables several programs to run at the same time
process
when some of the program instructions are running
what is process management
since the main memory is too small to run all the processes, the operating system uses multi-processing to allocate the use of the main memory and the CPU.
what is hardware management?
when the operating system manages input and output from hardware devices and the use of any resources needed by a process
input/output management
device drivers allow devices created by different manufacturers to communicate
resource management
the operating system allocates the required resource to the processes that are currently running. Internally, the operating system ensures that any data and/or instructions in main memory do not conflict with each other, and allocates the memory that the process requires
user interface management
operating systems provide interfaces to users of the computer system, allowing them to communicate with the hardware. The operating system uses abstraction to hide complexity from the user
the two types of interface
- graphic user interface (GUI)
2. command line interface/interpreter (CLI)
graphical user interface (GUI)
a desktop view where everything is displayed and use WIMP (windows, icons, menus and pointer) to describe the features of this interface
Applications run in windows and all objects (apps, hardware and files) are represented by icons.
Application features are accessible through the use of menus.
Users interact with the interface by using a mouse and onscreen pointer.
GUIs are powerful and easy to use but require a lot of processing power
command line interfaces
CLIs are text based. Users control the computer by typing in commands.
CLIs require little processing power and are extremely powerful
but they take longer to learn how to use than GUI
they exist within modern operating systems e.g. the command prompt app in windows, and terminal in macOS
utility software
helps maintain the system
what is utility software used for?
- compression
- defragmentation
- backing up
- anti-virus
- anti-spyware
T/F most basic utility is part of the operating system, but additional utilities can also be installed separately
true
data compression
compression software reduces the size of a file on secondary storage
why do we have data compression?
smaller files are easier to transmit across a network as they require fewer packets to be sent. Their reduced size also means more files can be stored in any given area of storage
fragmentation explanation
when a file is stored on a hard disk it is not stored as a whole file, but as a series of segments. Sometimes the segments run together in sequence and sometimes are split up over a disk
fragmentation
the storing of a file in several separate areas of memory scattered throughout a hard disk.
why can fragmentation make a computer run slower?
over time, more and more files become fragmented. A fragmented disk takes longer to read from and write to making a computer run slower
defragmentation
defragmentation takes the fragmented files and rearranges the segments so that they run contiguously, This decreases the read/write time, thereby speeding up computer performance
why do we need data back up?
data can be lost accidentally or deliberately. A user may accidentally delete or overwrite a file or a hard disk may fail, preventing access to any files stored on it. A hacker or malicious user may deliberately delete or overwrite data
why do we need data back up?
data can be lost accidentally or deliberately. A user may accidentally delete or overwrite a file or a hard disk may fail, preventing access to any files stored on it. A hacker or malicious user may deliberately delete or overwrite data
data back up
regular copies of the data are made to prevent data loss. if data loss occurs, data can be retrieved from backup. The software allows all backed up files to be retrieved, or just special files
what are the two types of back up that are possible?
full backup
incremental backup
full backups
involves making a copy of every file on the computer network. This can require a lot of storage space and can be consuming to make
incremental backups
incremental backups take a copy of any new files created since the last backup and of any files that have been edited, such as user documents
how do network managers ensure all data is backed up and daily backups are small and less time consuming?
most network managers make an initial full backup and then switch to daily incremental backups
anti-virus
scans the computer system, with when activated or automatically at a specific time and identifies potential viruses. Many anti-virus software can delete or fix potential threats.
why do we need anti-spyware?
spyware installed without the knowledge of the user, designed to collect data about the user such as personal info or bank details that can be passed on in identity theft.
anti-spyware
anti-spyware software can find, then delete, the spyware. Some versions can prevent it being installed in the first place
simulation
computer simulation can be used to simulate and model aspects of the real world. Simulation is used to test a theory before it is turned into a physical or practical form
why is simulation useful?
physically dangerous situations can be prevented
different simulations can give options that can help decision making
unnecessary costs can be avoided
modelling
a model is a representation of a real life situation
