when compiling programs, I getting this error

/usr/bin/ld: cannot find -lncurses
collect2: ld returned 1 exit status
** Unable to rebuild library /appo1/bnk/bnk.run/lib/lib41.so.27 *

You have not installed all the dependencies the software needs.

You must read the documentation that comes with the source code. Typically, you will find a list of software that must be installed to support the program you are trying to compile. That information can be found in the README, INSTALL, or other files at the top-level of the source directory. Also, the project's web page will likely tell you what pre-installed software is necessary.

The error is telling you that your machine does not have the ncurses library installed.

If you are using a Debian-based distribution, you should be able to install it by running (as root):
If you are not using a Debian-based distribution, then you need to search for the name of the package that provides the ncurses libraries.

Be aware that you may need to install other dependencies after ncurses. That is why you need to read and understand the documentation.

Better : # apt-get install libncurses-dev

Or # yum install ncurses-devel ( If Fedora based OS.)

I.e. the "-devel" packages are required, when compiling.

Indeed.

I should clarify my response so that anyone that reads this isn't left with half the story (in a manner of speaking). The original error was:
This error is caused by the linker. Creating a binary executable requires roughly two stages: compiling and linking--in that sequence.

The "-devel" packages contain source code files useful for the compilation stage. The source code in the "-devel" packages identify what external support is available to the program (such as ncurses terminal-drawing capabilities).

The linking stage no longer relies on source code, but rather, connects the new program with pre-compiled libraries. The pre-compiled libraries contain the machine code instructions that actually provide the support the new program wanted.

When creating a new binary, you typically need both: the "-devel" packages associated with a support library and the library itself.

Because the error above was a linker problem, the compiling would seem to have finished without error. That said, there are instances where a compiler warning has caused one of my own compile jobs to fail at the linking stage.

Anyway, the moral of the story is: install both source/development packages (for the source code) and the libraries itself.

Thanks for ur explanation Mr.Dark Helmet.