When a process is terminated, the shell only stores an 8-bit return code, but sets the high bit if the process was abnormally terminated. But because your process is terminated by a segmentation fault, usually the signal that is sent is SIGSEGV(Invalid memory reference) which has a value of 11.
So because your process was terminated abnormally, you have a 128 and then you add the value of the signal that terminated the process which was 11, you get 139.
