In IRIS GL, you use variations on the v function to specify vertices. The equivalent OpenGL function is glVertex: Below are examples of glVertex.
glVertex2[d|f|i|s][v]( x, y );
glVertex3[d|f|i|s][v]( x, y, z);
glVertex4[d|f|i|s][v]( x, y, z, w);
The glVertex function takes suffixes the same way other OpenGL calls do. The vector versions of the call take arrays of the proper size as arguments. In the 2-D version, z=0 and w=1. In the 3-D version, w=1.