Computing F453

Computing F453

1. Operating Systems

   • Single User / Single Use
     • Old Nokia
     • Only performs one task at one time. With one on screen task at one time for one person at one time.
   • Multi-User / Multi Tasking
     • Found in mainframes and super computers
     • Example
       • Central Processor
         • Terminal A
         • Terminal B
         • Terminal C
         • Shares Processor time
           • Each time slice allocated to each processor is a quantum
     • Thin client
       • The operating system has to manage:
         • Each user logged in
         • allocate resources
         • Keeps logs
         • Maintain security
         • Content switching
           • For it to switch between processes from terminal A and terminal B it has to store the information that it was processing from terminal A and terminal B. So it dumps the information of A into server storage so it processes B etc.
   • Network OS
     • Has to have following features
       • Deal with users logging on
       • Maintain the network connections to the server(s)
       • Expand the file system to view fo,lders on other computers
       • Provide security to separate user accounts
   • Batch OS
     • The name given to the job of doing a task over and over again.
       • Once stared it will run until completed.
       • Resource intensive.
   • Kernel
     • Handles
       • Loading /Unloading applications from memory
       • Scheduling tasks to run on the CPU
       • Memory Management
       • File Management
       • Data security
     • Device Drivers
       • A driver allows the operating system to communicate with it.
       • There could be hundreds of device drivers pre-installed with the operating system.
         • The exact details are stored by the operating system in window its called the registry.
   • User Interface
     • Menu Driven
     • Graphical Interface
     • Command Interface

2. Processor

   • Scheduling
     • Processes
       • Status
         • Indicates if the process is Running, Waiting (Blocked), or Ready
       • Registers
         • A copy of all the CPU registers when the process last ran in the CPU. These will be re-loaded into the CPU when the process is ready to run
       • Unit of processing time
         • Lets the scheduler know how much time the process has had to run so far
       • Awaiting
         • If the process is in the WAITING / BLOCKED state, it identifies which resource the process is waiting for. In this case the process is waiting for a keyboard input
       • Link to other PCB
         • A queue is a kind of list data structure. Lists are easily handled if each item in the list can point to the next one
     • Purpose
       • Process as many jobs as possible
       • Make maximum use of CPU time
       • Be responsible to the user so that they are unaware to the delay of the process
       • Make maxium use of resources
       • Be fair to all jobs
       • BE able to priotrise
       • BE able to alter priorities
       • Avoid Deadlock

3. Stacks

   • Stacks are first in last out
   • Lists
     • Static vs Dynamic
       • Static
         • Advantages: Complier can allocate space during complaction, Easy to program, Easy to check for overlow.
         • Disadvantages:
       • Dynamic

4. Spooling

   • Printing
     • printing jobs takes a long time to complete, a utility accepts print jobs any jobs that are currently running.
       • The spooller stores a que in a tempoary storage area, it works on a first-in, first-out basis.
         • On a single machine the spooler runs as a background task.
           • But on a network it runs on a dedicated server, which runs on behalf of all indivual computers
             • Jobs run with priority so certain jobs will run before others.
       • This allows the computer to be used whilst the printer is printing
   • Booting
     • When the PC is switched on the memory is blank and the CPU doesn't know anything.
       • BIOS, Basic input output system. This find all the connected memory and drives etc.
         • Booting allows the operating system to be loaded from initial switch on
         • When a computer is switched on it sends a reset signal to the ram to clear it.
     • POST
       • Includes checks: Memory, system clock, processor, keyboard, screen display, BIOS isn't corrupted
       • This happens very quickly and if any errors occurs a 'beep' or error message is displayed.
     • BOOT STEPS
       • Finds bootable media
         • Finds the boot sector and therefore the MBR
           • The MBR shows the bootloader location
             • The bootloader then loads windows.
           • The Master Boot Record (MBR) is a table which shows partitions, file system type, sector sizing