what's unit of vertex that has been transformed?

what's unit of vertex that has been transformed?
The following code fragment is the part of code of theTutorial 2.
struct CUSTOMVERTEX
{
FLOAT x, y, z, rhw; // The transformed position for the vertex.
DWORD color; // The vertex color.
};
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZRHW|D3DFVF_DIFFUSE)
CUSTOMVERTEX vertices[] =
{
{ -1.0f,-1.0f, 0.0f, 0xffff0000, },
{ 1.0f,-1.0f, 0.0f, 0xff0000ff, },
{ 0.0f, 1.0f, 0.0f, 0xffffffff, },
};
The vertices in the preceding code fragment have been transformed.they ara already in 2d window coordinate.This means that the point (0,0) is at the top left corner and the positive x-axis is right and the positive y-axis is down.
My question is what's unit of vertex?Is it pixel?If "1.0f" means one pixel?

[904 byte] By [elemr] at [2007-12-23]