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I am a beginner to C and I am trying to understand the comparison function needed for the qsort function. Part One: Syntax A simple suggested use is this (I have included some main() code to print the results as well): #include <stdio.h> #include <stdlib.h> int values[] = { 40, 10, 100, 90, 20, 25, 12, 13, 10, 40 }; int compare(const void *a, const void *b) { const int *ia = (const int *)a; // casting pointer types const int *ib = (const int *)b; return *ia - *ib; } int main() { int n; for (n=0; n<10; n++) { printf("%d ",values[n]); } printf("\n"); qsort(values, 10, sizeof(int), compare); for (n=0; n<10; n++) { printf("%d ",values[n]); } printf("\n"); system("pause"); return 0; } I don't understand why you need all the extra things in the compare function so I simplified it to this: int compare (int *a, int *b) { return *a-*b; } This still works, and produces the same results. Can anyone explain to me what I removed, and why it still works? Part Two: Why Pointers? Additionally, do I really need to use pointers? Why can't I just compare "a" and "b" directly like so (this does NOT work): int compare (int a, int b) { return a-b; } For some reason, with a multidimensional array, I was able to get away with NOT using pointers and for some reason it worked! What is going on? (Example code of sorting a multidimensional array by the 2nd item in each sub array): #include <stdio.h> #include <stdlib.h> int values[7][3] = { {40,55}, {10,52}, {100,8}, {90,90}, {20,91}, {25,24} }; int compare(int a[2], int b[2]) { return a[1] - b[1]; } int main() { int n; for (n=0; n<6; n++) { printf("%d,",values[n][0]); printf("%d ",values[n][1]);

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