Where does the k prefix for constants come from?

Question

it\'s a pretty common practice that constants are prefixed with k (e.g. k_pi). But what does the k mean?

Is it simply that c

Answer 1

It's a convention, probably from math. But there are other suggestions for constant too, for example Kernighan and Ritchie in their book "The C language" suggest writing constants' name in capital letters (e.g. #define MAX 55).