| ??? 12/05/05 22:23 Read: times |
#104740 - Hard and Soft Responding to: ???'s previous message |
Craig Steiner said:
The definitions I've seen of RTOS are along the lines of "An OS that provides a certain capability within a specified time contraint" or "An OS that operates in an environment whereby the failure to respond within a given time constraint results in critical failure."
Notably absent is any specific time constraint. In fact, given these vague and non-specific definitions, even Windows could be considered "real-time" by these definitions if the time constraints are loose enough. Quite right, and in RTOS circles a further distinctiion is made between hard and soft real time systems based on the consequences of missing a deadline. If they are catastrophic, the system is said to be hard real time, and if the consequences are simply an irritation, like a printout is delayed for a few seconds, it is said to be a soft real time system. So on that basis windows is a soft real time system. I suspect the term real time in computer circles was coined to distinguish such systems from the (then common) batch systems where you submitted your job to the computer operator and, with luck, picked up the results the next day. As this industry has advanced extemely rapidly it is not surprising that terms which were quite meaning full when coined now seem vague. I strongly suspect that the term multi-tasking was coined first because I know for certain it was used in 1971 by ICL well before the first micro saw the light of day. Ian |
