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what is an operating system (OS)

A software that controls the general function of a computer and provides an easier way for users to interact with computers and run applications

how may an OS benefit users

it hides the complexities of computer hardware

what does an operating system provide

human-computer interfaces (HCI), this is either graphical user interface (GUI) or command line interface (CLI)

what is a human-computer interface

an environment for a user to interact with the machine

what is a GUI

it allows users to interact with computers through symbols or pictures, which would execute steps without the user needing to write them

what is a CLI

a text-only service that require users to type out the commands wanted.

what are the disadvantages of a CLI

users must know a number of commands and type them out with no mistakes just to carry out basic operations, meaning it takes longer

what’s an advantage of CLI

direct communication, less memory used, and users aren’t limited to predetermined options

what are the types of management carried out by the OS

memory, file, hardware, process, and security

what is memory management

the management of a computer’s main memory. It’s broken down into memory optimization, organisation and protection

what is memory optimisation

it controls how memory is allocated/ deallocated when multiple applications are running at the same time. It also chooses where they’re stored in memory

what is memory organisation

it determines how much memory is allocated to an application and how it can be split up in the most efficient way

what is memory protection

it ensures two applications cannot use the same memory location at the same time. Otherwise data could be lost, there may be security issues or the computer may crash

what does security management do

it ensures the integrity, confidentiality and availability of data

what are some tasks performed by security management

it carries out OS updates, ensures anti-virus software is always up to date, communicates with a firewall to check all traffic, and maintains access rights for all users. It also prevents illegal intrusion, offers data recovery, and uses privileges to prevent users from accessing areas they aren’t allowed on

what does process management do

allocates resources and permitting data to be shared/ exchanged, allowing all processes to be synchronised

what does hardware management involve

all input and output peripheral devices

what are some functions of hardware management

It communicates with devices via device drivers, which use this to translate file data into a format the device can understand. It also ensures each hardware resource has a priority, so it can be used and released as required

what are some tasks file management carry out

it defines the file name, maintains directory structures, and ensures control mechanisms are maintained. It also performs specific tasks on files, specifies the logical file storage format based on the disk formatter used, and ensures memory allocation for a file by reading it from HDD/ SSD and loading it into memory

what are utility programs and what are some examples

they’re part of the OS. Some examples are a hard disk formatter, virus checker, file compression and defragmentation, repair, back-up softwares,

what is a hard disk formatter

It gets the HDD ready for use by first splitting it into partitions which are formatted. This file system is based on a table of contents that allow the OS to recognise a file and where it’s stored

what tool does a hard disk formatter contain

a checking tool that is carried out on each sector. Bad sectors are flagged as bad and the file tracking will be reorganised by replacing it with new unused ones, repairing it. A damaged file will now contain an empty sector, meaning it can be read but it’s corrupted because the bad sector contained the important (now gone) data. Therefore, the file should be deleted too

what are virus checkers

antivirus software offered by the OS that is in the background and constantly checking for viruses. They need to always be kept up to date

what are some tasks performed by an antivirus software

it checks files/ programs before they are ran or loaded on a computer, compare possible viruses against known one and put potentially infected files in quarantine

what is defragmentation software

it reorganises scattered data into contiguous blocks, reducing HDD head movements and improving overall performance

what’s another operation defragmenters can perform

clean ups, where data blocks can be damaged after too many read/write operations and are labelled unusable and are avoided. This is different to bad sectors

what happens when a HDD gets full

blocks used for files are scattered all over the disk surface which happens when files are deleted or extended. This causes slower data access time as the head requires more movement

what is disk content analysis/ repair software

it checks disk drives for space and usage by reviewing files and file folders. Unwanted files and downloads can be removed, optimising the use of disk space

why is file compression useful

it’s essential to save storage space and it makes it quicker to download or upload files

what does the OS back-up utility do

it allows a schedule for backing up files to be made, but a back-up procedure will only occur if there have been changes made to a file

how many versions of a file should there be

three - the current one, the locally backed up one, and the remotely backed up one

what is a program library

a library on a computer that stores programs/ routines and are free for others to use

when are program libraries used

when users can use pre-written code to shorten development time and when DDL subroutines are used and needed at run time

how do program libraries improve the development of software

routines don’t need to be rewritten each time and they’ve already been tested/ should be error free. This saves development time and cost

what are the two types of program libraries

static and dynamic

what are static libraries

when software is linked to executable code in the library at time of completion

what are dynamic libraries

software isn’t linked to the library routines until run time. As these routines are stand-alone files that are only needed when required by the program, it can be shared to many applications at the same time

what are the advantages of a dynamic library

routines aren’t loaded into memory till required, so memory is saved and the software runs faster. Executable code is much smaller, you can change DDL files independently from the main program, and it’s available to many applications at the same time, all this save memory/ execution time

what are the disadvantages of using a dynamic library

the executable code is not self-contained so all DLL files must be available at run time or error messages will show and the software could crash. If the DLL files are changed an unexpected result may be given by the main program or it could crash. Lastly, malicious changes may be due to malware, presenting a risk to the main program after the linking process.

what is an assembler

a program that translates assembly language into machine code, to be either stored in main memory for execution or in a storage medium for later.

how may high language be translated into machine code

via a compiler or interpreter program

what do both compilers and assemblers need for when

when they store a program in a storage medium, a loader program is needed to load it into main memory. This stored program can also be executed without it needing to be retranslated, only when changes are made

how does an interpreter work

it executes a program line by line every time its run, it doesn’t generate a translated program

how does an assembler translates instructions compared to a compiler or interpreter

an assembler does 1-1 translation, one line of source program is one line of machine code, whereas a compiler/ interpreter produce many machine code instructions

what is an IDE

an integrated development environment, it’s a bunch of programs to help write/ test a computer program written in high level language

what are the benefits of a compiler

it only generates executable code, so users can’t alter the program and developers can charge for updates. It also has quicker execute time, optimises code, programs have no errors and it can be translated on one computer and executed on another

why do compilers have a quicker execute time

translation is completed and programs can be run immediately, whereas interpreters need to translate it line by line before it can be executed

what are the disadvantages of compilers

it may find errors that aren’t errors, untested programs with errors may cause the computer to crash, users are reliant on the developer, and errors are only shown after the whole program has been translated

what are the disadvantages of interpreters

users need to purchase a compiler/ interpreter to translate the source code program before it’s used, developers can’t charge for updates, it takes longer to execute, it can still contain errors, and it cannot be interpreted on one type of computer and run on another

what are the advantages of interpreters

Untested programs shouldn’t be able to make the computer crash, partial results can be viewed during development, and it’s easier to edit or debug as errors can be corrected at each line and restarted from that point

how do IDEs typically use a compiler and interpreter

an interpreter during development, and a compiler during execution

some high language programs use what

partially compiled/ partially interpreted), i.e. java and python

how may an IDE be used for coding

its context sensitive prompts

what do IDEs usually have

a source code editor, either or a compiler/ interpreter, a run--time environment with a debugger and an auto-documenter

what is a source code editor

it allows a program to be written/ edited without the use of a separate text editor, speeding up development. Some use pretty printing, offer context sensitive prompts as well as dynamic syntax checking

which IDE feature may be used for coding

context sensitive prompts

what is a run-time environment with a debugger

a program that runs while a program is being developed, aiding with debugging. It allows users to single step and set a breakpoint. After, a report window is shown, allowing users to check for logic errors and to make sure the program works as wanted

what features of an IDE is used in debugging

single stepping (running a program one line at a time), breakpoints (a pause in execution to inspect content), and a report window (a separate window that shows the contents of variables during execution)

what is an auto-documenter

it explains the function/ purpose of code

what features of an IDE is used for presentation

prettyprinting (where code is formatted to be more visually appealing/ easier to read) and the collapsing or expanding code blocks

what feature of an IDE is used during initial error detecting

dynamic syntax checking, which finds syntax errors as the program is being typed out and alerts the user. Logic errors on the other hand can only be found when a program is run

what are some ways an IDE can be used

coding, initial error detection, presentation, and debugging