DECC$UMASK

   DECC$UMASK specifies the default value for the permission mask
   umask. By default, a parent C program sets the umask from the RMS
   default permissions for the process. A child process inherits the
   parent's value for umask.

   To enter the value as an octal value, add the leading zero;
   otherwise, it is translated as a decimal value. For example:

   $ DEFINE DECC$UMASK 026

   Maximum: 0777