1.2.1 Systems Software

Interrupts are signals generated by software or hardware to indicate to the processor that a process needs attention.

Multilevel Feedback Queues make use of multiple queues, each which is ordered based on a different priority.

• Printers, • graphics cards, • and network cards.

• Testing programs, • checking for malware, • and running software compatible with different versions.

It is straightforward to implement but does not take in mind job priority.

It takes into consideration different job priorites. But it is difficult to implement.

All processors get a fair share of the CPU but choosing the right time quantum can be difficult.

• It is suited to batch systems, as waiting time is reduced; • but it requires processor to calculate how long each job will take; • and it does not take into account job priority or urgency.

• Throughput is increased as shorter processes can be quickly completed… • but it does not take into account job priority or urgency, • and processor starvation can occur if short jobs are continuously added to the queue.

• It provides interrupt service routines, • manages processor scheduling, • manages backing stores, • and provides a user interface.

A Bootloader is a small program that loads the Operating System into the RAM when the computer is switched on.

A Bootstrap is a series of programs that initialise the Operating System during startup.

A device driver is a piece of software that enables communication between an operating system and a specific hardware device.

A Distributed Operating System is an operating system which can run across multiple devices.

Multi-tasking operating systems enable the user to carry out tasks seemingly simultaneously.

A Multi-User Operating System is when multiple users make use of one device.

A Real Time Operating System is designed to perform a task within a guaranteed time frame.

An Embedded Operating System is built to perform a small range of specific tasks and catered towards a specific device such as a household appliance.

An Operating System is a collection of low-level software which manages the operations of the device.

The Basic Input Output System is the first program that runs when a computer system is switched on.

Disk thrashing is when the computer ‘freezes’ due to pages being swapped too frequently between the hard disk and main memory.

First Come, First Served is a scheduling algorithm wherein jobs are processed in chronological order by which they enter the queue.

Intermediate Code is code that is halfway between machine code and object code.

• Organise the use of main memory and allocates memory, • convert logical addresses to physical addresses, • allows programs to share memory, • protect programs and data from each other, • and allows programs larger than memory to run.