Api not accessible

It is little bit difficult for me to explain this scenario. I have a project developed by manufacturers and i downloaded and it compiles with their project environment. They provide some API which i can use within that project in other source files by calling the Api. They have not provided the source code for the same. I dont find the object file also. It is accessible only for price. Now my question is i create a new project can i use those Api ? I tried but it is not compiling. Is it possible to hide like that, i mean to say you can hide obj file also ? Or i am missing something ? Please advise.

Well, if the only thing you have is the DLL file, then you may have to load the library manually.
Using Run-Time Dynamic Linking | Microsoft Docs

It is an embedded project for micro controllers i am not sure if DLL files will be available for them.

Look for a static library.

Yes the static library did the job. Thanks.