HLSL is analogous to the GLSL shading language used with the OpenGL standard.
It is very similar to the Nvidia Cg shading language, as it was developed alongside it.
Early versions of the two languages were considered identical, only marketed differently.
[3] HLSL shaders can enable profound speed and detail increases as well as many special effects in both 2D and 3D computer graphics.
Note that games may claim to require a certain DirectX version, but don't necessarily require a GPU conforming to the full specification of that version, as developers can use a higher DirectX API version to target lower-Direct3D-spec hardware; for instance DirectX 9 exposes features of DirectX7-level hardware that DirectX7 did not, targeting their fixed-function T&L pipeline.