the answers are very clear already, but I'll just add that if you force the Raisonance compiler to be ANSI, it will enforce some potentially "code inflating" techniques such as forcing promotions and making all functions reentrant, while at the same time still allowing some 8051 specific keywords such as "interrupt" (whose imlementation may differ from one compiler to another)

As for Sieve, I see a total size of 989 bytes (that can still be reduced by 4% using CodeCompressor) that seems too low (even for me!): maybe we are not using exactly the same source (or maybe it's due to a very modular printf function)

Regards,

Luca