If the keyboard working properly with other programs, then try to disable anti-keylogging features in your antivirus.
Eg :- Quick Heal (antivirus vendor name) blocked the keyboard for all applications without a trusted publisher (in this case Turbo C++ ).
FAQ
1. What is keylogging?
Keylogging refers to using software to record everything you type on your keyboard, when that software is open.
2. Why you need to disable anti-keylogging?
This is happens because of DOSBOX. DOSBOX uses keylogging to transfer your keystroke to Turbo C++.
DOSBOX is emulating tool which run 16-bit application on 32/64-bit OS. We used it to run Turbo C++ on 32/64-bit OS.
3. Is disabling anti-keylogging is safe?
Yes. You can disable anti-keylogging when you are using the Turbo C++ and enable it again when you are not using Turbo C++.