Operating System

Operating System

1. Printing

   • If my program needs to print a document, I tell the operating system to print it. The operating system will then spool the print job (it will keep it in a queue until the printer is ready) This means my program doesn’t need to worry if the printer is busy or unplugged or out of ink.

2. Peripherals

   • A peripheral is a device that is attached to the computer, such as a webcam or a memory stick. Operating systems require driver software for each device. A device driver maps the operating system's commands to the device's commands. For example it contains the specific machine code needed to print a specific character on that brand of printer.

3. Backing Stores

   • Backing stores are storage devices used to keep backups of important files Operating systems can often manage this for the user The OS will make regular backups in the right format an appropriate device (Cloud, Tape or Disk)

4. File compression

   • File compression is storing data in a way that keeps the same information but uses less disk space.The same information is stored, but the second way uses fewer bytes. Operating systems can compress data as it’s saved and decompress it as it’s loaded, allowing more data to be stored on a device.

5. Disk de-fragmentation

   • Disk defragmentation involves re-arranging file fragments on a physical disk surface to improve load times This will be looked at in greater detail in the Utility Software lesson.

6. Memory (RAM)

   • In order to ensure there is enough memory for each program that is running, Ram is split into “pages” Each page is presented to its program as if it is the only memory the system has. This prevents programs from snooping on data from other programs.

7. Processes (multi-tasking)

   • Modern processors can execute 4 billion instructions every second. This is more than memory and secondary storage can keep up with While a processor waits for other components to catch up, it is not doing anything
   • Multi-tasking is where a processor appears to be doing two tasks simultaneously In reality the processor runs commands from each task separately, filling in the time when it is waiting for other components.

8. Security

9. Desktop Devices Windows Mac OS Linux Unix Portable Devices Android iOS Chrome OSThey perform a range of functions: Managing Resources Processes Peripherals Memory Provide an interface

10. Machine code instructions are different for each piece of hardware Each PC has a different combination of CPU, hard disk, memory manager, graphics card etc. An operating system talks directly to the hardware. Software is written for the OS instead of the hardware.