a= 0002,  b= 0002
a*b= 00000004 

a= 4000,  b= 4000
a*b= 10000000 

a= FFFF,  b= FFFF
a*b= 00000001 

a= FFFF,  b= 0001
a*b= FFFFFFFF 

a= 0001,  b= FFFF
a*b= FFFFFFFF 

a= 5536,  b= 3655
a*b= EE026EEE 

a= 3655,  b= 5536
a*b= 1215AEEE