So, how do the so-called real time signals differ from the regular standard signals; the following table reveals this:
| Characteristic | Standard signals | Real time signals |
| Numbering | 1 - 31 1 | 34 - 64 2 |
| Standard first defined in | POSIX.1-1990 (it's old) | POSIX 1003.1b : real time Extensions to POSIX (2001) |
| Meaning assigned |
Individual signals have a particular meaning (and are named accordingly); the exception is SIGUSR[1|2] |
Individual RT signals have no particular meaning; their meaning is app-defined |
| Behavior when blocked and multiple instances of same signal continuously delivered | Out of n instances of the same signal, n-1 are lost; only 1 instance is kept pending and delivered to the target process ... |
