The default spectrum file format saved by the MAESTRO software (made by ORTEC/Ametek Inc) is called an "integer spectrum data file" that is is saved in a file with the CHN extension to the file name. Documentation of the CHN file format can be found in the ORTEC Software File Structure Manual.
For your convenience, I wrote a C++ class to parse the content of such a file which you can find below. Below the C++ class, there is a small test program to read a CHN spectrum and print out the channel data.
Do you have suggestions for improvements or bugs to report? Then please comment below.