Added first source file, more to come...

factorials.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[])
+{
+    unsigned long long int n;
+    n = atoll(argv[1]);
+    int start = n;
+     
+    for (int i = 1; i < start; i++)
+    {
+        n = n * i;
+    }
+    printf("%llu\n", n);
+    return 0;
+}