Shop1_3 - Arrays/Linked List/Binary Search Tree

This is a compilation of shop programs I wrote in 3 different ways or better said data structures from scratch. Shop 1 is implemented with an array. When the program starts it allocates memory on heap and gives 100 possibly entries of products (during runtime it is not possible to customize it). Shop 2 is implemented using a doubly linked list and therefore it is possible to allocate memory during runtime. Shop 3 is implemented using a binary search tree.To keep things simple I decided to sort products by a code value, so when displaying products on the screen, they will be printed out in an increasing order. I have also omitted a sort option from the program.