The distinction between "function" and "procedure" doesn't map very well to whether the return type is void in C's syntax: - On one hand, a lot of "functions"

The distinction between "function" and "procedure" doesn't map very well to whether the return type is void in C's syntax: - On one hand, a lot of "functions" are actually procedures that just happen to return a value: think for example `write(2)`, which is clearly used for its side effect, not to compute how many bytes could be written -- even though that's what it returns. - On the other hand, you can have a "procedure" (i.e., a function "returning" void) that actually has no side effects other than storing a computed value in a specified location (e.g. void square(int x, int *ret) { *ret = x*x; }). That's clearly a function in the mathematical sense, even though it "returns void".