In these cases Ken Thompson and Dennis Ritchie favored simplicity over perfection. The Unix system would occasionally return early from a system call with an error stating that it had done nothing—the "Interrupted System Call", or an error number 4 (codice_1) in today's systems. Of course the call had been aborted in order to call the signal handler. This could only happen for a handful of long-running system calls such as codice_2, codice_3, codice_4, and codice_5. On the plus side, this made the I/O system many times simpler to design and understand. The vast majority of user programs were never affected because they did not handle or experience signals other than codice_6 and would die right away if one was raised. For the few other programs—things like shells or text editors that respond to job control key presses—small wrappers could be added to system calls so as to retry the call right away if this codice_1 error was raised. Thus, the problem was solved in a simple manner.