  This is the third part of a series of articles providing a foundation for the
theory of Drinfeld modular forms of arbitrary rank. In the present article we
construct and study some examples of Drinfeld modular forms. In particular we
define Eisenstein series, as well as the action of Hecke operators upon them,
coefficient forms and discriminant forms. In the special case A=F_q[t] we show
that all modular forms for GL_r(\Gamma(t)) are generated by certain weight one
Eisenstein series, and all modular forms for GL_r(A) and SL_r(A) are generated
by certain coefficient forms and discriminant forms. We also compute the
dimensions of the spaces of such modular forms.
