IB Computer Science HL Paper 1 Topic 6

Resources that need to be managed in a computer system

• Primary memory (RAM / Cache / ROM)

• Secondary storage

• Processor speed

• Bandwidth

The use of paging in the management of primary memory

• It is used in the formation of virtual memory to increase the amount of primary memory

• The OS copies as much data as possible into RAM, and leaves the rest on the disk

• Memory is divided into pages and transferred in and out of the RAM (exchange between RAM and disk) as requires

Polling

* A technique which allows one unit to check the status of another unit at regular intervals

Protocol

* A set of standards to coordinate data transmission

Why protocols are necessary

• To ensure data integrity

• To control data flow

• Minimalise congestion

• To allow communication

Functions of an OS related to multitasking

• Memory management - allocates separate memory to each program / process, allowing programs to share memory

  • The system will moved to paging if it beings to run out of shared memory

• Processor management - allows the appearance of more than one program running at the same time by allocating time slices for parts of each program

  • Arranges the execution of applications so that the user believes several programs at once are running

  • Prioritises tasks by importance

Interrupts

• A signal to the CPU to hardware or software to alert the CPU to stop execution of the current program and transfer control to the interrupt handler, and execute the higher priority task

• The previous order of tasks is saved to the interrupt stack, so it can resume once the interrupt has been serviced

Policy

* User specified values to help guide a machine’s mechanisms

Scheduling

* The process by which tasks are assigned computer resources to compute

Operating system resource management techniques

• Scheduling

• Policies

• Multitasking

• Paging

• Interrupt

• Polling

• Virtual memory