diff --git a/c_modern_approach/Pointers/theory.c b/c_modern_approach/Pointers/theory.c
new file mode 100644
index 0000000..a730bb0
--- /dev/null
+++ b/c_modern_approach/Pointers/theory.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+void decompose(double, long *, double *);
+
+int main() {
+  long mp;
+  double rm;
+  double x = 3.141234;
+  printf("%ld, %f\n", mp, rm);
+  decompose(x, &mp, &rm);
+  printf("%ld, %f\n", mp, rm);
+}
+
+void decompose(double x, long *int_part, double *frac_part) {
+  *int_part = (long)x;
+  *frac_part = x - *int_part;
+}