Every Prospero client must call the function p_initialize() before making any calls to Prospero library functions. Your program may well crash weirdly if you don't.
extern void p_initialize(char *software_id, int flags, struct p_initialize_st * arg_st);
If you're writing a client, send email to firstname.lastname@example.org and request a software ID string. If you're just experimenting with the libraries, you can pass a NULL pointer or empty string as the software ID. At the moment, no flag values are defined, and no members of the structure for additional arguments are defined, so the most common calling sequence is:
p_initialize((char *) NULL, 0, (struct p_initialize_st *) NULL);