ROSHINA HARAM

ROLL NO# 31

BS(TS) 3rd

www.BZUpages.com

OPERATING SYSTEM

Real time operating system.

Two types of real time operating system:

1. Hard real time (periodic)

2. Soft real time (aperiodic)

SOFT REAL TIME SYSTEM

A soft real time system in which missing an occasional deadline is acceptable

For example digital audio or multimedia falls in this category.

VxWorks and QNX are well known operating systems.

We can also say that:

Soft real time task has an associated deadline that is desirable but not mandatory, it still makes sense to schedule and complete the task even if it has passed its deadline

Soft real time system

Soft real time systems are typically those used where there is some issue of concurrent access and the need to keep a number of connected systems up to date with changing situation

Soft real time system

For example:

1 : The software that maintains and updates the flight plans for commercial airlines.

2 : Live audio ,video systems are also usually soft real time system

Design philosophies

Two basic designs exist:

Preemptive priority

round robin

SCHEDULING

The real key is designing the scheduler.

Data structure of the ready list in the scheduler is designed to minimize the worst case length of time spent in the

schedulers critical section

SCHEDULING

Real time scheduling

Deadline scheduling

Rate monotonic scheduling

Earliest deadline first scheduling

Priority inversion

SHUKRIYA