Question

Given the following pseudo-code below with nested subprograms,

(a) Under static-scoping rules, what will be printed out?

(b) Under dynamic-scoping rules, what will be printed out?

(c) Name a disadvantage of dynamic scoping.

 var x, y;

                       function  sub2() {

                                              var y;

                                              y = 10;

                                              document.write("x = " + x + "" + “y = “ + y + “ “);

                       }

                       function  sub1() {

                                              var x;

                                              x = 30;

                                              document.write("x = " + x + "" + “y = “ + y + “ “);        

                                              sub2();

                                              document.write("x = " + x + "" + “y = “ + y + “ “);

                       }

                       x = 20;

                    y = 50;

                       sub1();

Answer 1

Static Scoping: Look for the definition within a block then enclosing block then global variables.

Dynamic Scoping: Look for the definition within a block then enclosing block then calling Function then global variables.