I written this code and it compiles just fine. However, when I tried to include <stdio.h> library to use with my hyperterminal, it says that it compiled, but can not link. Here is the message that it gave me... ERROR L107: ADDRESS SPACE OVERFLOW SPACE: DATA SEGMENT: _DATA_GROUP_ LENGTH: 0070H My memory model is "Small: variables in DATA". When I changed it to compact or large, my program will compile and link, but it behaves differently when I put program it to the Philips 89C664.. thanks Tommy