RIP with 64-bit x86
The "Write great code" series of books is a must read for those interested in low and "high" level concepts.
x86-64 ("x64") versions of Windows can run x86-32 binaries.
Actually, there even today exist quite some vocal Windows users who would love to run some really old 16 bit applications on their 64 bit Windows PC (but Microsoft stopped supporting running 16 bit binaries on 64 bit Windows versions).