What are the historical reasons C languages have pre-increments and post-increments?

Question

(Note: I am not asking about the definitions of pre-increment vs. post-increment, or how they are used in C/C++. Therefore, I do not think this is a duplicate question.)

Answer 1

When you count down from n it is very important whether is pre-decrement or post-decrement

#include 
void foopre(int n) {
    printf("pre");
    while (--n) printf(" %d", n);
    puts("");
}
void foopost(int n) {
    printf("post");
    while (n--) printf(" %d", n);
    puts("");
}
int main(void) {
    foopre(5);
    foopost(5);
    return 0;
}

See the code running at ideone.