How do I concatenate a string and an integer to make a filename? [duplicate]

Your original question title was a little mis-leading because all you actually want to do is concatenate a string and an integer.

In C++ you would probably do that with stringstream:

stringstream ss; ss << "New" << l << ".bmp"; 

And then to get a string variable:

string filename = ss.str(); 

And finally to pass a C string to the SDL function use c_str():

SDL_LoadBMP(filename.c_str()) 

The declaration of DDBImage is wrong. You need an array of length 10, but you declared it to have length 9. If you made LengthFiles into a constant you could write SDL_Surface *DDBImage[LengthFiles] and so be sure that the array was the correct length.

The code might then look like this:

const int FileCount = 10; SDL_Surface *DDBImage[FileCount]; for (int index=0; index<FileCount; index++) { stringstream ss; ss << "New" << index << ".bmp"; string filename = ss.str(); DDBImage[index] = SDL_DisplayFormat(SDL_LoadBMP(filename.c_str())); } 

If your file names really start with New1.bmp then you'll need to adjust the indexing:

ss << "New" << index+1 << ".bmp"; 

Finally, if you need to extend this to handle a variable number of files, determined at runtime, then you should use vector<*DDBImage> instead of a raw array. Using vector<> allows you to let the C++ standard library take care of low-level memory management for you. In fact any time you find yourself allocating memory when programming in C++ you should ask yourself if there is already some part of the standard library that will do it for you.