The Mac OS X Kernel is a hybrid based on the XNU kernel derived from the former NextStep implementations. Much of the code is open source and freely available. (See links below)
Mac OS X is based on the XNU kernel, a microkernel Mach kernel with a BSD userland, which makes Mac OS X's kernel a hybrid-kernel.
Mac OS X is built on the XNU (X is Not Unix) kernel which is a hybrid combining elements of the Mach kernel and FreeBSD.
Mac OS X uses a Mach kernel and FreeBSD utilities at it's core.
Mac OS X is the operating system used by G5 Macs. The latest version of Mac OS X that will work on a G5 is Mac OS X 10.5 (also known as Leopard).
Unix
Mac OS X use Mach kernelmore about Mach: http://en.wikipedia.org/wiki/Mach_kernel
Updating to the latest version of Mac OS X will provide you with the latest printer software. HP keeps a selection of software for various versions of Mac OS X. (See links below)
The latest trend in operating system is the ability to connect with most devices. These is what is known as compatibility of the operating system.
The reason for the exec functions being same/similar is because the Mac OS has its roots in variants of the Unix kernel.
OS X was forked from the FreeBSD 2.x/3.x branch. with kernel mods and the quartz userland. the various OS X releases have corresponding FreeBSD releases. it uses the FreeBSD mach microkernel with os9 compatibility. Darwin is the development builds of OS X versions. the FreeBSD guys backport OS X tech into their OS. OS X is opensource aside from the quartz userland. OS X also includes kernel components from the NeXT step operating system.
Mac OS X 10.4 "Tiger" will run on a PowerPC G4/800MHz machine. It is the latest OS that Apple will support on that processor, however. At this writing (January 2010), Mac OS X 10.4.11 is the latest version of Tiger.
Osx snow leopard I think ^^^^Thats wrong the answer is OS X Lion :)