Embedded Electronics-Real-time software-Introduction

In computer science, real-time computing (RTC), or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints, often referred to as "deadlines". Real-time responses are often understood to be in the order of milliseconds, and sometimes microseconds. Conversely, a system without real-time facilities, cannot guarantee a response within any timeframe (regardless of actual or expected response times).
The use of this word should not be confused with the two other legitimate uses of 'real-time'.

=-Related Posts:
Embedded Systems Programming and Simulation Using Flow Code
Karnaugh_Maps-Digital Electronics Tutorials
Micro-controllers-Basic Introduction Tutorials
In the domain of simulations, the term means that the simulation's clock runs as fast as a real clock. In the processing and enterprise systems domains, the term is used to mean 'without perceivable delay'.

Real-time software may use one or more of the following: synchronous programming languages, real-time operating systems, and real-time networks, each of which provide essential frameworks on which to build a real-time software application.

"Software that must read input changes when they occur and change outputs predictably,within a certain time limit"

• Real-time software programming is typically driven by interrupts
• Not necessarily fast code – simply has to meet time constraints

Three classes of real-time systems

1. Hard real-time = Failure results in a catastrophe, loss of human life.Examples- Nuclear reactor, Aeroplane etc.
2. Soft real-time = Failure results in loss of data, loss of value.Examples-Airline reservation system, stock market etc.
3. Best-effort = No penalty for missing time.Examples-Email, web surfing etc.