code::blocks multiple programmes under a single project

[extraordinaryrabbani]

I have started using code::blocks for practicing ,(was using bloodshed dev C++ til now)
the thing is that m not able to complie multiple programmes stored under a single project , as i have created project by the name of a topic and have decided to solve all problems related to that topic under that project.
when there was only one .cpp file in the project it compiled successfully ,but as soon as i created a second file and compiled it it says "main can be declared only once"

[MiiNiPaa]

m not able to complie multiple programmes stored under a single project

One project is intended to be one program (executable, library, etc.)
Just create another project for second problem. You can separate different topics by storing projects in different folders (like topic1/project1 topic1/project2 topic2/project1 ...) or create different workspaces for each topic.