The original version of Ultima I was written in a mixture of BASIC and assembly. BASIC is pretty slow, but most BASIC implementations let you call into optimize

The original version of Ultima I was written in a mixture of BASIC and assembly. BASIC is pretty slow, but most BASIC implementations let you call into optimized assembly routines. Though, past a certain point of complexity, performance aside, assembly might be more readable than BASIC because BASIC relied on line numbers for jumping around, whereas assemblers offered named labels.