"Linux was one of the first cross-platform operating systems to
use 64-bit processors, and now 64-bit systems are becoming
commonplace in servers and desktops. Many developers are now facing
the need to port applications from 32-bit to 64-bit environments.
With the introduction of Intel Itanium and other 64-bit processors,
making software 64-bit-ready has become increasingly important.
"As with UNIX and other UNIX-like operating systems, Linux uses
the LP64 standard, where pointers and long integers are 64 bits but
regular integers remain 32-bit entities. Although some high-level
languages are not affected by the size differences, others such as
the C language may be..."