Why is tolower behave different???

[merriman at ccavax.camb.com]

In article <2841 at elrond.CalComp.COM>, 
	shodsdon at elrond.CalComp.COM (Steve V. Hodsdon) writes:
> I just finished porting a software package that ran on a VAX 11/780
> to a Sun SPARCserver. One of the programs would not run. (Could not find
> the filename specified.). The program was looking for a certain extension,
> but could not find it.
> 
> Finally, it dawned on me that the function call tolower was to blame.
> On the VAX, the call did nothing if the char was already lowercase, while
> the Sun converted it anyway.

Converted it to what?