MD5 different standards?

Are there different MD5 standards?

The rfc (http://www.faqs.org/rfcs/rfc1321.html) says:

The algorithm takes as input a message of arbitrary length and 
produces as output a 128-bit [= 16 bytes] "fingerprint" or "message 
digest" of the input.

My IDE's MD5 function produces 16 bytes.  Yet for pgsql MD5 should 
produce 32 bytes.

Can I find a human language description of this 32 bytes MD5 
somewhere, so that I can implement it myself.  I'm not good at 
reading C.  (Where did you guys get your info to implement it for 
pgsql?)

Thanks,

Marc