// BSS variables are defined to have a starting value of zero.
   // (I forget where that's defined; maybe ANSI... in any case, where it
   // is, they're most likely called unintialized globals, or something...)
   
     Just remember that this is not true on all operating systems.  Once
   I had a program that worked perfectly on NetBSD but did not work on
   SunOS 4.1.2.  The problem: non-initialized variables that should have
   zeros as value...

were these variables globals or per-function stack variables ?

stack variables are a very different matter, but, BSS variables
are defined to be zero, initially.