getc() and putc() can be implemented as macros in standard C (although a non-macro version needs to be supplied as well), so I think the author was trying to ex

getc() and putc() can be implemented as macros in standard C (although a non-macro version needs to be supplied as well), so I think the author was trying to explain why getc() may appear slower in some circumstances than others. Of course, nowadays, it would be difficult to measure the difference between a macro getc() and a function getc().