It is a hashmap, using linear probing on an array
Use unsigned int for the keys/hashes.
Make functions like get, display or exists const, so you make clear that they are not modifying the map and you can pass the map as const&amp; to a function, which may uses this functions but does not use add or remove or other functions modifying the map.

void display() const;

You can add operator[] which returns a reference to the value, here are the signatures:

int&amp; operator[](int key); // this can be used for assignment (``map[3] = 5``) and to get a value (``std::cout &lt;&lt; map[3] &lt;&lt; '\n'``). This needs to insert an element, if there is no element with the key and initialize its value to a default value like ``int()``/``0``
int operator[](int key) const; // this is used when the map is accessed when it is const. No need for reference, but for other value-types like std::string, use std::string const&amp; to avoid copying

You can make the class generic, to allow other value-types.
Make whitespace after each function or class, to seperate.