UDI is a library of C routines which provides a machine-independent programming environment. It allows a coherent software approach for developing and maintaining digital signal processing algorithms on stand-alone workstations or on host/array processor configurations. UDI is devoted to sound signal analysis and synthesis, but can be used by any application which does vector math calculation. It facilitates the porting of software, and has already been ported to nine different machine configurations. In order to use UDI, you should have a basic knowledge of C programming, but it is possible to perform simple operations directly from a command-line interface without writing a program (see chapter ``Unix Command-line Interface'').