This is happens because of DOSBOX. DOSBOX is emulating tool which run 16-bit application on 32/64-bit OS. DOSBOX specially design for gaming and only for keyboard interactions.
We used it run Turbo C++ on 32/64-bit OS. So, you need to use Turbo C++ Keyboard shortcuts. For menu you can use Alt+First later of menu item name.
For Example -
- For Run Menu ->
alt+r - For Compile Menu ->
alt+c
When menu is open you can use top-down arrow and enter key to select an option. You can find the list of all shortcuts of Turbo C++ here.