add changes to sqlite_ex and some new files

rudimentary_calc.c

@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int main() {
+  double sum = 0, val;
+
+  while(scanf("%lf", &val) == 1)
+    printf("\t%.2f\n", sum += val);
+  return 0;
+}