Abstract: In this paper, the software of the HP 9845 microcomputer data system of the MAT 261 solid isotopic mass spectrometer is analyzed. Its structure, advantages and disadvantages are viewed. On base of the analysis, the software has been modified in part, and has been developed to the new improvement program NINT 10. The main features of the NINT 10 are saving the memories, speeding up execution and more functions. Main modified parts are described.