diff --git a/code/info2/inter.h b/code/info2/inter.h
index 8dd0bdd4e..c112cf860 100644
--- a/code/info2/inter.h
+++ b/code/info2/inter.h
@@ -5,6 +5,11 @@
 // tablice x[] i y[] zawieraja wspolrzedne wezlow interpolacji
 // n liczba wezlow interpolacji
 // xx wartosc dla ktorej liczy sie wielomian
+
+// function computing values of Lagrange interpolation polynomial
+// arrays x[] i y[] contain coordinates of predefined interpolation nodes
+// n is number of interpolation nodes
+// xx value of independent variable for which the value of polynomial is computed
 double lagrange( double *x, double *y, int n, double xx );
 
 #endif