Software Flashcards
When are interrupts checked for
at the end of each FDE cycle
Uses of virtual machines
- used on networks to avoid redundant processors
- translating code (Java)
- running different operating systems
boot up process of a computer
- POST is run
- clears anything in the registers
- loads the address of the first instruction of the boot program into the PC
- the boot program checks for start-up instructions on the BIOS
- The OS kernel is loaded
Uses of Embedded operating systems
Washing machines, vending machines, car engine systems, traffic lights, pay and display machines
Uses of Multi-tasking operating systems
desktops and smart phones
Uses of real-time operating systems
Airline control, theatre bookings, heart monitors, production lines, radar systems
Uses of Multi-user operating systems
schools and offices
Use of distributed operating systems
Data centres, large companies, weather/financial modelling, data mining trend finding
functions of an OS (8)
- Provides a user interface
- manages security
- provides a platform for utilities/applications
- manages external devices
- managing the processor/scheduling
- managing memory
- provides a platform for networking
- managing hardware
How does Java use virtual machine?
the virtual machine execute intermediate code (Java Byte code)
Device drivers are…
hardware dependent and OS specific
Multi-level feedback queue
uses multiple queues based of the priority of the process.
Non pre-emptive algorithms
- First come first serve
- shortest job first
Pre-emptive algorithms
- Round Robin
- Shortest Remaining Time
- Multi-level feedback queue
Pre-emptive
Once a process has entered the running state it can be stopped
Aims of scheduling
- to provide an acceptable response time to all users
- To maximise the time the CPU is usefully engaged
- To ensure fairness on a multi-user system
What happens if an interrupt is detected?
- the contents of all the registers are pushed onto a stack
- The interrupt service routine is run
- Once complete the values of the registers are popped off the stack back into the registers
What does an OS provide?(4)
- User interface
- Memory Management
- Interrupt handling
- Processor scheduling
What loads the OS into RAM
the bootloader
Library Programs (System Software)
contains useful functions that are frequently used by programs. Simplifies the process of application development.
Operating system (System software)
software that allows the user to control the computer with ease. It provides a virtual machine hiding the true complexity of the computer from the user and manages and controls access to the computer’s resources.
examples of system software
Operating system, Utility Program, Library Program, Translators.
system software
operates, controls and maintain the computer and its components.
Hardware
the physical components of the computer system.
Software
program code. Sequences of instructions which are executed in order to perform a task.
Backing Up
programs which allow for manual or automatic backing up of files onto another disk, on the existing computer system, to a removable device such as DVDs or CDs, to a network file server or to a cloud based storage system online
Firewalls
a program that blocks unauthorised access onto a network by inspecting packets to find the port they are attempting to access through.
If the port is blocked then the packet is rejected.
file managers
programs which allow users to easily copy, delete, rename and modify files on a computer system
compression
programs which attempt to reduce the amount of physical space that files take up when they’re stored
fragmented disk
over time a disk becomes fragmented as old files are deleted and new files are added, free space often becomes scattered across a disk and a program has to be split and spread across a disk to fit. The more fragmented the slower the computer performs
Disk defragmentation
programs which attempt to consolidate the spilt files and free space. therefore reading and writing files becomes more efficient.
Antivirus utility software
programs which help to detect and remove malicious programs which are often designed to harm the computer.
Utility software
Small programs that perform a specific task usually related to the maintenance and upkeep of the computer system.
factors to consider when choosing applications (5)
- functionality
- hardware
- availability
- cost
- reliability
types of application software (12)
word processors desktop publishing programs spreadsheets database management Slideshow and presentation Multimedia and video editing photo and graphics manipulation communications, chat and IM social networking email clients web browsers Gaming
application software
software that allows the user to do or make something.
Open Source Software
any software which is supplied along with its original source code.
e.g. Linux
Closed Software
software which is supplied pre-compiled. The source code is not available and often copyrighted, also known as proprietary software
e.g. microsoft word
Benefits of Open source software
- usually free
- users are free to amend the source code and tailor the program to their needs
- not constrained by commercial considerations
- many people are continuously finding and fixing bugs
drawbacks of open source software
- can be less user friendly/less easy to use
- less support available
- people may exploit failures maliciously before they are fixed
Benefits closed source software
- companies have a lot of resources providing security if the program doesn’t work, service/support, and a more polished user friendly product
Drawbacks of closed source software
- costs money, can be expensive
- small range of versions of software
translator
any program that converts source code into machine code. e.g. interpreters, compilers and assemblers
assembler
converts low level assembly language directly into machine code.
compiler
converts high level code to object code.
interpreter
takes one line of high level source code and converts it directly into machine code then runs it.
machine code
code that the processor understands, made of a opcode and operand