diff --git a/src/simpleFile.cpp b/src/simpleFile.cpp
index 9d1991a..ff0b857 100644
--- a/src/simpleFile.cpp
+++ b/src/simpleFile.cpp
@@ -1,4 +1,9 @@
 #include <armadillo>
+#include <cmath>
+#include <fstream>
+#include <iomanip>
+#include <ios>
+#include <string>
 
 arma::vec* general_algorithm(
     arma::vec* sub_diag,
@@ -21,18 +26,73 @@ arma::vec* special_algorithm(
 
 }
 
-arma::vec* error(
+void error(
+    std::string filename,
+    arma::vec* x_vec,
     arma::vec* v_vec,
     arma::vec* a_vec
 )
 {
+    std::ofstream ofile;
+    ofile.open(filename);
+
+    if (!ofile.is_open()) {
+        exit(1);
+    }
+
+    for (int i=0; i < a_vec->n_elem; i++) {
+        double sub = (*a_vec)(i) - (*v_vec)(i);
+        ofile << std::setprecision(8) << std::scientific << (*x_vec)(i)
+            << std::setprecision(8) << std::scientific << std::log10(std::abs(sub))
+            << std::setprecision(8) << std::scientific << std::log10(std::abs(sub/(*a_vec)(i)))
+            << std::endl;
+    }
+    
+    ofile.close();
 
 }
 
-double time() {
+double analytic_solution(double x) {
+    return 100*std::exp(-10*x);
+}
+
+void build_array(
+    int n_steps, 
+    arma::vec* sub_diag, 
+    arma::vec* main_diag, 
+    arma::vec* sup_diag,
+    arma::vec* g_vec
+) 
+{
+    sub_diag->resize(n_steps-2);
+    main_diag->resize(n_steps-1);
+    sup_diag->resize(n_steps-2);
+
+    sub_diag->fill(-1);
+    main_diag->fill(2);
+    sup_diag->fill(-1);
+
+    g_vec->resize(n_steps-1);
+
+    double step_size = 1./ (double) n_steps;
+    for (int i=0; i < n_steps-1; i++) {
+        (*g_vec)(i) = analytic_solution((i+1)*step_size);
+    }
 
 }
 
-int main() {
+int main() 
+{
+
+    arma::vec sub_diag, main_diag, sup_diag, g_vec;
+    int n_steps;
+    // Timing
+    for (int i=1; i <= 6; i++) {
+        n_steps = std::pow(10, i);
+      
+
+        // construct arrays
+
+    }
 
 }