add iterative_fibonacci.c in C

fibonacci_series/C/iterative_fibonacci.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdint.h>
+
+int fib() {
+  int n;
+  printf("Please indicate the fibonacci number you would like to find: ");
+  scanf("%d", &n);
+  printf("The fibonaaci number at postion %d: ", n);
+  if (n <= 1) {
+        printf("%d", n);
+        return 0;
+    }
+  else {
+    int64_t first = 0, second = 1, result;
+    for (int i = 0; i < n; i++) {
+          result = first + second;
+          first = second;
+          second = result;
+      }
+      printf("%ld", result); 
+    }
+  return 0;
+} 
+
+int main() {
+    fib();
+    return 0;
+}