Leading underscore in variable name

Hi,

I try to investigate a program written by a former collegue.

An 8-bit dipswitch is connected to the microcontroller address/data bus. Two variables are declared in an assembler file: public DIPSWITCH and public _DIPSWITCH. The dipswitch value is read bij an assembler file from address DIPSWITCH (the real hardware address) and stored in _DIPSWITCH. (_DIPSWITCH is to be used as the startup dipswitch value and DIPSWITCH is used as the real actual value).
In a .C file both DIPSWITCH and _DIPSWITCH are declared as 'extern xdata unsigned char'.
If I evaluate the startup value _DIPSWITCH in that .C file I get the actual value of DIPSWITCH.
If I create only two code-lines:

 if ( _DIPSWITCH){ do something}
 if (  DIPSWITCH){ do something}

and then I compile that source with '#pragma src' and look in the listfile I see:

 MOV DPTR,#_DIPSWITCH
 MOV DPTR,#_DIPSWITCH

So both different .C source lines compile to the same assembler code.

Can someone explain this?

Thanks

Henk