On my system (Gentoo Linux PPC, GCC 2.95.3), Hugs goes into an infinite loop while parsing the Prelude file. The problem is in input.c, lines 515 and 516: lineBuffer[lineLength] = fgetc(inputStream); if (lineBuffer[lineLength] == EOF) The value of EOF cannot be stored in a char on this system, so 'lineBuffer[lineLength] == EOF' always evaluates to 0. Here's a fix: int ch = fgetc(inputStream); lineBuffer[lineLength] = ch; if (ch == EOF) Glad to help, Jeff Binder