This document contains the code for analyzing the geometric and material nonlinearity of springs under displacement-controlled loading. The code imports input data on spring properties and stress-strain behavior, performs an incremental analysis to calculate the base shear and displacement at each step, and exports the results to Excel and MATLAB files. Negative or invalid input values trigger error messages. The analysis calculates the strain, stiffness, and force in each spring at each increment until the ultimate displacement is reached.