1.5 Systems Software

1) Operating system - provides a platform on which users can run programs 2) Utility software - used to maintain the computer system

An Operating System (OS) is a complex piece of software found on most computer systems

1) Communicate with internal and external hardware via the device drivers 2) Provide a platform for different applications to run 3) Allow the computer to multi-task by controlling memory resources and the CPU 4) Deal with file management and disk management

1) GUI (graphical user interface) 2) Command line interface 3) Menu interface 4) Natural language

1) Windows, icons, menus, pointers (WIMP) 2) Visual, interactive and intuitive 3) Optimised for mouse and touch gesture input

1) Text based 2) Less resource heavy compared to a GUI 3) More commands than a GUI 4) Efficient 5) For advanced users 6) Useful for automating processes with scripts

1) Successive (consecutive/sequential) menus presented to the user 2) Single options chosen at each stage 3) Often with buttons as a keypad

1) Responds to questions in spoken language 2) Not always reliable 3) Getting better all the time

1) Running multiple applications at the same time by giving each application a small time slice of processor 2) this allows more than one program to be held in memory at a time, and data shared between them such as copy and paste 3) It also enables you to listen to music on your PC at the same time as word processing

1) When programs are loaded, the operating system decides where they are held in memory 2) Over time, the memory becomes fragmented as programs are loaded and closed because they use different amounts of memory 3) The operating system must keep track of different program fragments 4) When the memory is full, the operating system uses virtual memory

1) Translates operating system instructions into commands that the hardware will understand 2) Each peripheral needs a device driver 3) Many are already built into the operating system (data is transferred between devices and the processor, this process must be managed)

1) Providing for different users to log into a computer 2) The operating system will retain settings for each user (e.g. icons, desktop backgrounds etc.) 3) Each user may have different access rights to files and programs 4) A client-server network may impose a fixed or roaming profile for a user and manage login requests to the network

1) Data is stored in files 2) An extension to the filename tells the operating system which application to load the file into 3) The operating system may present a logical structure of files into folders and allow the user to rename, delete, copy, and move files

1) A program which performs important maintenance tasks to improve the performance of a computer system 2) Computers often come with utility software and how this performs housekeeping tasks 3) Utility software is needed to perform additional tasks that may not be carried out by an operating system

1) Encryption utilities use an algorithm to scramble plain text into cipher text 2) The text can only be decrypted and made readable again with a key

1) Defragmentation utilities reorganise files on a hard disk, putting fragments of files back together, and it collects together free space 2) This reduces the movement of a read/write head across the surface of the disk, which speeds up file access

1) Compression utilities reduce the size of a file so that it takes up less space and is quicker to download over the Internet 2) Compressed files must be extracted before they can be read 3) Depending on the algorithm used, data is either lost (reducing the quality of an image/sound e.g. JPEG) or represented in a different way using binary, retaining the original data in a new, compressed format (e.g. Zip)

1) Solid state drives should not be defragmented 2) It is unnecessary as they have no moving parts 3) It also reduces their lifespan