art@acc.arpa (05/21/87)
>VAX/VMS is extremely inefficient at creating new processes. When the >VMS command interpreter executes a user program, it does not create a >new process, but simply does the equivalent of a UNIX exec() system >call. Thus the current invocation of the command interpreter >effectively dies and is replaced by the user program. (How it regains >control after the user program terminates is a long, long story that >I don't fully understand.) In VMS, interactive processes are created by LOGINOUT. The process is created with the "Command Line Interpreter" (usually DCL) mapped into the P1 part of the address space where it executes. When an image (program) is run, it is loaded and mapped into the process address space and entered. When the process exits, control returns to DCL which has always been there. DCL is also entered via callback for command parsing and ^Y will interrupt back to DCL (and CONTINUE returns you to the image). Art@ACC.ARPA ------