SYSTEM SOFTWARES

SYSTEM SOFTWARES

1. OPERATING SYSTEMS

   • manages access to the hardware in the computer
   • operating systems provide an application programming interface (API)
     • this is a set of code libraries that software developers can use to write applications for that operating system
   • SYSTEM MANAGERS
     • the operating systems are in charge of many pieces of hardware each of which is controlled by a dedicated manager
       • the user interface manager (UI) provides the user interface which allows them to be used by applications
         • USER INTERFACES
           • COMMAND LINE INTERFACES
             • CLI is an environment where the computer is controlled by typing text commands using the keyboard
             • computer cannot display graphics, only text
             • CLIs use less memory than graphical interfaces
           • WIMP
             • stands for window-icon-menu-pointer
             • applications can be seen in movable, resizable windows
             • programs and documents are represented by icons
             • options are available via menus
             • user interaction is through a moving pointer
           • GRAPHICAL USER INTERFACES
             • GUIs are modern environments to work in
             • these are usually based on the window-icon-menu-pointer (WIMP) paradigm or a multi-touch interface
       • the device manager allocates resources to external hardware devices and allows them to be used by applications
         • PURPOSE OF DEVICE MANAGER
           • keeps track of which devices are connected to which ports
             • it takes care of peripherals such as keyboard, mouse, printer, webcam
           • allows applications to read or write data to each device
       • the memory manager controls the allocation of the memory between applictions
         • PURPOSE OF MEMORY MANAGER
           • controls the allocation of RAM to each running process
           • if the memory manager fails to manage memory well, then the computer will slow down and might crash
       • the user manager authenticates and separates users of the computer.
         • PURPOSE OF A USER MANAGER
       • the process manager controls the allocation of central processing unit (CPU) cycles to multiple running applications
         • PURPOSE OF PROCESS MANAGER - (resposible for: CPU allocation and multitasking)
           • modern operating systems allow users to run multiple programs at once
             • this is known as multitasking; for this to work, the OS must manage how memory and CPU time is allocated to each running process
           • really, a CPU can execute only one process at a time, so the CPU switches between processes so quickly that it seems that they are running simultaneously
       • the file manager controls the opening, reading and writing of files in secondary storage
         • PURPOSE OF A FILE MANAGER
           • responsible for determining the type of a file, and sending it to the correct application
             • it decides if a file can be Read, Modified or Executed
           • keeps track of where specific files and folders are located in secondary storage

2. UTILITY SOFTWARE

   • Used to perform specific tasks to help maintain the system
     • BACKUP - makes copies of data that can be restored in the evnt of data loss
     • COMPRESSION - applies an algorithm to reduce the space needed to represent a file or its contents
     • DEFRAGMENTATION - improves hard disk performance by applying an algorithm to reorganise data
       • frangmentation - files arre written to a secondary storage and are not always written in a continuous block
         • if a file is stored in different places on a storage device, the file is fragmented
         • fragmented files take longer to load
       • defragmentation software reorganises data on the storage device -> storage in the files in stored in adjacent blocks
         • defragmentation software will increase the performance of the computer
     • ENCRYPTION - prevents unauthorised access to files by applying an algortihm to 'scramble' data
       • decryption is when an authoried party uses a special key to unscramble data
         • the key prevents unauthorised users from accessing the data
         • good encryption utilities will work closely with the OS to encrypt and decrypt files in real time as you need to access them
       • works by applying special algorithm to the data
       • very mathematical processes

3. DEVICE DRIVERS

   • used to tell the operating system how to use a piece of hardware
     • also tells the operating system how to understand the data coming from the device and what format it expects to receive data in
   • works closely with device manager

4. USER MANAGEMENT

   • Single-user operating system
     • is an OS which supports one user at a time
     • it may or may not allow multiple user accounts, although only one may use the system at once
   • Multi-user system
     • allows several users to be connected at the same time
   • PUEPOSE OF USER MANAGER
     • keeps track of which users can accsess the system and who is currently logged in
     • handles authentication and logging in
     • responsible for making decisions based on access rights