SPICE input netlist is parsed to the compiled C++ simulator program to perform the transient analysis and to output the simulation result data to be plotted using MATLAB code.

       +---------+   +-----------+   +-------------+   
       |  SPICE  |   |    C++    |   | Output Data |   
       |  Input  |-->| Simulator |-->|  Plotting   |
       | Netlist |   |  Program  |   | with MATLAB |
       +---------+   +-----------+   +-------------+

All source files come under the header files: circuit.hpp and matrix.hpp where matrix.hpp comes under circuit.hpp file.

                    +-------------+
                    | circuit.hpp |
                    |      |      |
                    |  matrix.hpp |
                    |      |      |
                    |     *.cpp   |
                    +-------------+

circuit.hpp -> Contains the data structure to model circuits, its components and the simulation
matrix.hpp -> Contains the data structure for matrix representation of circuits to be used for matrix calculations to output the result

circuit.cpp: Contains fundamental function for conversion of netlist to circuit data structure
matrix.cpp: Contains fundamental function for conversion of circuits to matrix representations
matrix_update.cpp: Contains function that updates the circuit every timestep
matrix_solver.cpp: Contains solve_matrix function that finds the matrix representative of the given circuit and solves for all node voltages
matrix_current.cpp: Contains functions to find the current through different components
simulator.cpp: Contains the main function for simulation with all circuit updates and matrix computations for each timestep

Armadillo is a C++ Linear Algebra Library.
The documentation can be found in the link below.
http://arma.sourceforge.net/docs.html

#include <armadillo>
using namespace arma;

make 

./simulator <netlist.txt >output.txt 

make clean

Simulator outputs the time taken for simulation and the labels (voltage/current of the nodes/components) for each columns of data that was pipelined into output text file. This file can be loaded with MATLAB following the formats used by MATLAB files in the folder simulation_plot.