content chap 5

why does the computer system need an operating system

provides both the environment in which applications run and a useable interface that hides the complexity of the hardware

how is memory management carried out

management of computers main memory in three parts optimisation, organisation , protection

how is memory optimisation performed

how memory is allocated and deallocated when programs are simultaneously being ran

determines where programs are stored-keeps track of free memory and (swaps memory between ssd and hdd)

how organisation is performed

determines how much memory is allocated to an application

what are the different ways memory organisation can be performed

a single(contiguous) allocation

partitioned allocation

paged memory

segmented memory

what is single (contiguous) allocation

where al of the memory is made available to a single application

what is partitioned allocation

where memory is split into contiguous partitions and memory management then allocates a partition to an application

what is paged memory

partition allocation but each partition is fixed in size

what is segmented memory

memory is not contiguous each segment of memory will be a logical grouping of data(array)

how is memory protection performed

ensures two completing cannot use same memory location at the same time

how security management is performed

ensure integrity, confidentiality and availability of data

done by : carry out os updates and antivirus when available, maintaining access rights

how is process management performed

involves allocation resources and permits the sharing and exchange of data allowing for all processes to be synchronised

how is hardware management performed

communicates inputs and outputs with device drivers

translates data from a file into format that the device can understand

how is file management performed

defining file naming conventions

performing specific tasks such as creating opening deleting renaming

operations of hard disk defragmenter

organise storage space assigning partitions

checks and flags bad sectors as well

operations of a antivirus software

checks downloaded files

compare possible viruses against database of known viruses

carry out heuristic checking

quarantines

sometimes has a false positive however

operations of a disk defragmenter

rearranges blocks of data to store files in contiguous sectors where possible

makes retrieval much faster

use of disk content analysis

used to check disk drives for empty space

can lead to optimum use of disk space through removal of unwanted files

use of disk compression file compression

Disk compression works by identifying repeated or unnecessary data in files and storing it in a smaller encoded form

decompressing it back to its original state when accessed.

saves space

use of back up software

store three versions

current

locally backed up

remote back up

use of program libraries

utilising prewritten subroutines(library program) -save time

don’t need to test

have two libraries static(normal routines) or dynamic (DLL)

what are DLL files

library routine not linked until run time

pros of DLL

executable code is much smaller in the main memory as the files only loaded when run

save memory so saves execution time

cons of DLL

since dll isn’t embedded its more likely that it could be more vulnerable to malware

versions conflict one program might require different versions of the one dll

translator def

used to translate a source program written in any language other than machine code

interpreter def

computer program that analyses high level program line by line

compiler def

computer program that translates high level language to machine code

key characteristics of assembler

only does transition of assembly code

since instruction sets on all computers are different then its machine dependent

compiler pros interpreter cons

doesn’t gives/gives source control so could lose the ability to charge for intellectual property

runs each line every time its executed so takes longer

interpreter pros compiler cons

untested programs with errors might cause the computer to crash

easier to debug using an interpreter as errors can be corrected and the program restarted from that place vs compiler might not even find the correct number of errors

whats an ide

a set of programs to aid of the writing of programs

what does an ide contain

source code editor

compiler + interpreter

run time environment with debugger

auto documenter

what does a source code editor do

auto indentation

have prettyprinting

syntax checking and auto completing parts

what does a run time environment with debugger

aids debugging process

allows programmers to sort through errors line by line (single stepping) or to set a breakpoint where you can see a report window that shows contents of variables atp

what does an auto documenter do

explains the the function land purpose of programming code