The last couple of lessons have looked at operating systems. You can find revision notes here.

Description of the function of a bootstrap loader

The bootstrap loader is a small piece of the operating system that is stored in ROM. It is the first piece of software to be loaded after the computer is powered. It checks for an OS which can be located on Hard Drive, Floppy disk, Network, CD-ROM or even a USB flash drive.  It then loads this into RAM where the OS takes over.

Description and exemplification of the main functions of a single user operating system :

The operating system once loaded into RAM has 6 main functions, which allow it to manage the computer and allows the user to communicate with the hard ware.

Interpreting users commands

This is the area of the operating system that the user is most familiar with. The user controls the OS using a keyboard, mouse or other input device. These inputs are then passed to the correct part of the OS. Example clicking the save icon.

File management

The OS controls access to the backing storage devices, it maintains an index of the physical location on the backing storage of all the files. It controls access to these files on network operating systems. hierarchical filing systems can store files in Directories.

Memory  management

Each program can only be executed while in RAM. This part of the OS is responsible for making sure there is enough RAM  to store the program.  It also makes sure that programs do not use the same part of RAM. Areas of the hard drive are often used for virtual memory, this would be controlled by this and the I/O management.

Input/output management

This uses device drivers to allow communication with each device attached to the computer. It is responsible for the actual transfer of data and issues the appropriate control signals to the devices.

Resource allocation

Two processes can not use the same device at the same time. This section of the OS allows competing processes access to devices once they become available.

Managing processes

By allowing processes to share processor time, the OS can give the impression of multitasking. The state of each process is known and processor time can be give processes that require it.