general-purpose single packages (e.g. ALSCAL, PROXSCAL in SPSS; in the past, MDSCAL, KYST, POLYCON). These provide a common environment for a range of uses,  but only specified types of data can be scaled by a limited range of models, and they are susceptible to sub-optimal solutions

stand-alone special purpose programs come from sources  of very varying numerical reliability, have bewilderingly different conventions for data input, but do allow procedures to be fine-tuned to the particular data-type. By contrast ...

a library of 15 separate multidimensional scaling programs

each of which is used as a stand-alone program

with a common set of simple run commands

flexible output commands, and

extensive user-friendly and technical documentation.