PSn00bSDK is a 100% free and open source SDK project for the original Sony
PlayStation for developing homebrew applications and games for the console
100% freely. This SDK can be used for freeware, commercial, and open source
homebrew projects.

The SDK is composed mainly of libraries (libpsn00b) and some utilities that
provide a basic framework for developing software for the PlayStation
hardware, the compiler is separate (GCC) and should be acquired from GNU.
The library API is intentionally written to resemble the library API of the
official libraries as closely as possible. This design decision is not only
for familiarity reasons to experienced programmers, but also so that existing
sample code and tutorials would still apply to this SDK, as well as making
the process of porting over existing homebrew originally made with official
SDKs easier with minimal modification, provided it doesn't use libgs.

PSn00bSDK is currently a work in progress and cannot really be considered
production ready, but what is currently implemented should be enough to
produce some interesting homebrew with the SDK, especially with its extensive
support for the GPU and GTE hardware. There's no reason not to fully support
hardware features of a target platform when said hardware features have been
fully documented for years (nocash's PSX specs document in this case).

Most of libpsn00b is written mostly in MIPS assembly, moreso functions that
interface with the hardware. Many of the standard C functions are implemented
in custom MIPS assembly instead of equivalents found in the BIOS ROM, for both
stability (the BIOS libc implementation of the PlayStation is actually buggy)
and performance reasons.