Q: What was the entry keyword mentioned in K&R1?
A: It was reserved to allow the possibility of having functions with multiple, differently-named entry points, à la FORTRAN. It was not, to anyone's knowledge, ever implemented (nor does anyone remember what sort of syntax might have been imagined for it). It has been withdrawn, and is not a keyword in ANSI C. (See also question 1.12.)
K&R2 p. 259 Appendix C