PML is case sensitive. Function names are typically written in lower case. For example, functions like exp, sqrt, log, are lower case, because PML uses the standard C library, in which lower case is the norm. This differs from other programs like NONMEM which are not case sensitive. Spelling a function name incorrectly will result in a linker error message saying the function is undefined. Also, please note that the absolute-value function in C and PML is “fabs”, not “abs”, because it applies to floating-point values.