In this paper we show that Ultradistributions of Exponential Type (UET) are
appropriate for the description in a consistent way string and string field
theories. A new Lagrangian for the closed string is obtained and shown to be
equivalent to Nambu-Goto's Lagrangian. We also show that the string field is a
linear superposition of UET of compact support CUET). We evaluate the
propagator for the string field, and calculate the convolution of two of them.Comment: 30 page