System Software

System Software

1. Operating System

   • An operating system, sometimes called a platform, is a collection of programs that control the hardware in a computer or device.
   • The kernel is a computer program that is the core of a computer's operating system, with complete control over everything in the system.
   • Examples of operating systems: Windows: UNIX: MacOS:
   • The operating system is loaded from disk into RAM on the typical desktop or laptop computer.
   • The user interface is how the user interacts with the system. This can be provided as part of the operating system or can be a separate program running on top of the operating system.
     • All operating systems have a command line interface that allows the user to type in direct commands to access the operating system functions.
     • Windows® uses a graphical user interface (GUI) supplied as part of the operating system. A GUI uses icons (small pictures) to represent the resources and actions, reducing the need to learn commands. GUIs use mouse pointers or touch screens to select objects.
   • Memory Management = When a program is running it must be in the computer’s main memory and the operating system must manage where in memory each program and the data it needs must go.
   • A multi-tasking operating system allows several processes to be in RAM at the same time:
     • Running: The CPU is currently dealing with this process and others must wait.
     • Runnable: These are ready to go and just need the running program to finish or be interrupted to get the CPU’s attention so they can run.
       • Waiting: these processes are waiting to get into the queue and become runnable.
   • This tells the CPU to stop the running process as soon as it can and to deal with another process linked to the peripheral device. These programs are called device drivers.
   • User management enables a network administrator to set different access rights for different users.

2. Utility Software

   • Utility programs are designed to do just one or two tasks Utility software interacts with the computers hardware E.g. the Disk Drive, Utility programs can be stand alone but are also inbuilt in to the Operating System
   • Lossless The original file can be re-created as no data is lost
     • Lossy Some of the original data is lost and the original file can not be re-created
   • File Compression Disk Defragmentation File Repair Disk Copying Disk Formatting Disk Backup / Restore Anti-Virus
   • When a hard disk drive is new – files get added onto the disk in order – very much like starting with a blank piece of paper and adding to it As files are deleted – this leaves gaps When new files are saved – the files fill the gaps and become fragmented Defragmentation software groups fragmented files back together
   • Encryption means to scramble data in a way that it is unreadable to anybody who doesn’t have a key to be able to unscramble this.
   • Back-ups:Completed to ensure there is a way of restoring files/data/programs in case of computer failure
     • Full: A copy of all data and software on the hard disk drive / server is copied to a backup medium (e.g. an external hard disk drive / DVD-R) and the medium is kept at a different location Take a long time to complete (usually overnight) Recovery takes a long time as it restores all data and programs
       • Incremental: A full backup is made initially Each night only the files which have been changed since the last incremental back-up are copied Much faster to complete that full back-ups Takes much longer at restoring than a Full Back up as the full back up would need restoring first and then every incremental back-up since the last full back up