diff --git a/cnumber.hpp b/cnumber.hpp
index 815a495..3f30198 100644
--- a/cnumber.hpp
+++ b/cnumber.hpp
@@ -2,8 +2,6 @@
 #include "fractions.hpp"
 #include <iostream>
 
-using namespace std;
-
 class cnumber {
 private:
   fraction r, i;
@@ -78,7 +76,7 @@ public:
     return ratio;
   }
 
-  friend ostream &operator<<(ostream &os, const cnumber &z) {
+  friend std::ostream &operator<<(std::ostream &os, const cnumber &z) {
     if (z.r != 0) {
       os << z.r;
       if ((z.i.get_sign() == 1) && (z.i > 0)) {
diff --git a/fractions.hpp b/fractions.hpp
index 6e11858..96a16e1 100644
--- a/fractions.hpp
+++ b/fractions.hpp
@@ -2,8 +2,6 @@
 #include <iostream>
 #include <string>
 
-using namespace std;
-
 class fraction {
 private:
   signed long long n = 0;
@@ -15,7 +13,7 @@ private:
     return gcd(b, a % b);
   }
   int get_precision(double a) {
-    string s = to_string(a);
+    std::string s = std::to_string(a);
     int i = s.length() - 1;
     while (s[i] == '0') {
       i--;
@@ -108,10 +106,10 @@ public:
     fraction b(that.d, that.n);
     return a * b;
   }
-  friend ostream &operator<<(ostream &os, const fraction &q) {
+  friend std::ostream &operator<<(std::ostream &os, const fraction &q) {
     signed long long num = q.n;
     signed long long den = q.d;
-    string s = "";
+    std::string s = "";
     if (q.n < 0) {
       s = "-";
       num = num * -1;
@@ -121,7 +119,7 @@ public:
       den = den * -1;
     }
     if (q.get_sign() == 1) {
-      string s = "";
+      std::string s = "";
     }
     if (q.d == q.n) {
       os << s << 1;
diff --git a/main.cpp b/main.cpp
index bc949db..e147fa7 100644
--- a/main.cpp
+++ b/main.cpp
@@ -8,20 +8,20 @@ void cnumber_main() {
   cnumber a(3, 2);
   cnumber b(4, -3);
 
-  cout << "a = " << a << endl;
-  cout << "a* = " << a.conjugate() << endl;
-  cout << "a*a* = " << a * a.conjugate() << endl;
-  cout << "b = " << b << endl;
-  cout << "b* = " << b.conjugate() << endl;
-  cout << "b*b* = " << b * b.conjugate() << endl;
-  cout << "a + b = " << a + b << endl;
-  cout << "(a + b)* = " << (a + b).conjugate() << endl;
-  cout << "a - b =  " << a - b << endl;
-  cout << "(a - b)* = " << (a - b).conjugate() << endl;
-  cout << "a * b =  " << a * b << endl;
-  cout << "(a * b)* = " << (a * b).conjugate() << endl;
-  cout << "a / b = " << a / b << endl;
-  cout << "(a / b)* = " << (a / b).conjugate() << endl;
+  std::cout << "a = " << a << std::endl;
+  std::cout << "a* = " << a.conjugate() << std::endl;
+  std::cout << "a*a* = " << a * a.conjugate() << std::endl;
+  std::cout << "b = " << b << std::endl;
+  std::cout << "b* = " << b.conjugate() << std::endl;
+  std::cout << "b*b* = " << b * b.conjugate() << std::endl;
+  std::cout << "a + b = " << a + b << std::endl;
+  std::cout << "(a + b)* = " << (a + b).conjugate() << std::endl;
+  std::cout << "a - b =  " << a - b << std::endl;
+  std::cout << "(a - b)* = " << (a - b).conjugate() << std::endl;
+  std::cout << "a * b =  " << a * b << std::endl;
+  std::cout << "(a * b)* = " << (a * b).conjugate() << std::endl;
+  std::cout << "a / b = " << a / b << std::endl;
+  std::cout << "(a / b)* = " << (a / b).conjugate() << std::endl;
 }
 
 void fraction_main() {
@@ -33,20 +33,20 @@ void fraction_main() {
   fraction q(a, b);
   fraction q2(c, d);
   fraction q3(e);
-  cout.precision(10);
-  cout << a << "/" << b << '=' << q << endl;
-  cout << a << "/" << b << '=' << q.to_double() << endl;
-  cout << c << "/" << d << '=' << q2 << endl;
-  cout << c << "/" << d << '=' << q2.to_double() << endl;
-  cout << q << "+" << q2 << '=' << q + q2 << endl;
-  cout << q << "+" << q2 << '=' << (q + q2).to_double() << endl;
-  cout << q << "-" << q2 << '=' << q - q2 << endl;
-  cout << q << "-" << q2 << '=' << (q - q2).to_double() << endl;
-  cout << q << "*" << q2 << '=' << q * q2 << endl;
-  cout << q << "*" << q2 << '=' << (q * q2).to_double() << endl;
-  cout << q << "/" << q2 << '=' << q / q2 << endl;
-  cout << q << "/" << q2 << '=' << (q / q2).to_double() << endl;
-  cout << e << '=' << q3 << endl;
+  std::cout.precision(10);
+  std::cout << a << "/" << b << '=' << q << std::endl;
+  std::cout << a << "/" << b << '=' << q.to_double() << std::endl;
+  std::cout << c << "/" << d << '=' << q2 << std::endl;
+  std::cout << c << "/" << d << '=' << q2.to_double() << std::endl;
+  std::cout << q << "+" << q2 << '=' << q + q2 << std::endl;
+  std::cout << q << "+" << q2 << '=' << (q + q2).to_double() << std::endl;
+  std::cout << q << "-" << q2 << '=' << q - q2 << std::endl;
+  std::cout << q << "-" << q2 << '=' << (q - q2).to_double() << std::endl;
+  std::cout << q << "*" << q2 << '=' << q * q2 << std::endl;
+  std::cout << q << "*" << q2 << '=' << (q * q2).to_double() << std::endl;
+  std::cout << q << "/" << q2 << '=' << q / q2 << std::endl;
+  std::cout << q << "/" << q2 << '=' << (q / q2).to_double() << std::endl;
+  std::cout << e << '=' << q3 << std::endl;
 }
 
 void matrix_main() {
@@ -74,42 +74,42 @@ void matrix_main() {
   n[0] = c;
   n[1] = d;
 
-  cout << "The matrix m" << endl;
-  cout << m << endl;
-  cout << "The determinant of matrix m:" << endl;
-  cout << m.determinant() << endl;
-  cout << "The matrix n:" << endl;
-  cout << n << endl;
-  cout << "The matrix n roted by one pi radian:" << endl;
-  cout << n.rotate_by_one_pi() << endl;
-  cout << "The determinant of matrix n:" << endl;
-  cout << n.determinant() << endl;
-  cout << "The matrix n's transpose:" << endl;
-  cout << n.transpose() << endl;
-  cout << "The matrix n's diagonal:" << endl;
-  cout << n.get_diagonal() << endl;
-  cout << "The matrix n's off diagonal:" << endl;
-  cout << n.get_off_diagonal() << endl;
-  cout << "The vector d:" << endl;
-  cout << d << endl;
-  cout << "The matrix n * the vector d" << endl;
-  cout << n * d << endl;
-  cout << "The vector d * the matrix n" << endl;
-  cout << d * n << endl;
-  cout << "The matrix m * n" << endl;
-  cout << m * n << endl;
-  cout << "The matrix m + n" << endl;
-  cout << m + n << endl;
-  cout << "Is 2 an eigenvalue of m?" << endl;
+  std::cout << "The matrix m" << std::endl;
+  std::cout << m << std::endl;
+  std::cout << "The determinant of matrix m:" << std::endl;
+  std::cout << m.determinant() << std::endl;
+  std::cout << "The matrix n:" << std::endl;
+  std::cout << n << std::endl;
+  std::cout << "The matrix n roted by one pi radian:" << std::endl;
+  std::cout << n.rotate_by_one_pi() << std::endl;
+  std::cout << "The determinant of matrix n:" << std::endl;
+  std::cout << n.determinant() << std::endl;
+  std::cout << "The matrix n's transpose:" << std::endl;
+  std::cout << n.transpose() << std::endl;
+  std::cout << "The matrix n's diagonal:" << std::endl;
+  std::cout << n.get_diagonal() << std::endl;
+  std::cout << "The matrix n's off diagonal:" << std::endl;
+  std::cout << n.get_off_diagonal() << std::endl;
+  std::cout << "The vector d:" << std::endl;
+  std::cout << d << std::endl;
+  std::cout << "The matrix n * the vector d" << std::endl;
+  std::cout << n * d << std::endl;
+  std::cout << "The vector d * the matrix n" << std::endl;
+  std::cout << d * n << std::endl;
+  std::cout << "The matrix m * n" << std::endl;
+  std::cout << m * n << std::endl;
+  std::cout << "The matrix m + n" << std::endl;
+  std::cout << m + n << std::endl;
+  std::cout << "Is 2 an eigenvalue of m?" << std::endl;
   if (m.is_eigenvalue(2)) {
-    cout << "Yes!" << endl;
+    std::cout << "Yes!" << std::endl;
   } else {
-    cout << "No!" << endl;
+    std::cout << "No!" << std::endl;
   }
   if (n.is_hermitian()) {
-    cout << "The matrix n is hermitian, here is the hermitian conjugate:"
-         << endl;
-    cout << n.hermitian_conjugate() << endl;
+    std::cout << "The matrix n is hermitian, here is the hermitian conjugate:"
+         << std::endl;
+    std::cout << n.hermitian_conjugate() << std::endl;
   }
 }
 void vector_main() {
@@ -128,30 +128,30 @@ void vector_main() {
   w[0] = three;
   w[1] = four;
   w[2] = five;
-  cout << "v:" << endl;
-  cout << v << endl;
-  cout << "w:" << endl;
-  cout << w << endl;
-  cout << "v + w:" << endl;
-  cout << v + w << endl;
-  cout << "v - w:" << endl;
-  cout << v - w << endl;
-  cout << "v * w:" << endl;
-  cout << v * w << endl;
-  cout << "w * i:" << endl;
-  cout << w * i << endl;
+  std::cout << "v:" << std::endl;
+  std::cout << v << std::endl;
+  std::cout << "w:" << std::endl;
+  std::cout << w << std::endl;
+  std::cout << "v + w:" << std::endl;
+  std::cout << v + w << std::endl;
+  std::cout << "v - w:" << std::endl;
+  std::cout << v - w << std::endl;
+  std::cout << "v * w:" << std::endl;
+  std::cout << v * w << std::endl;
+  std::cout << "w * i:" << std::endl;
+  std::cout << w * i << std::endl;
   for (long long j = 0; j < v.get_dimention(); j++) {
-    cout << "Element " << j << " of v:" << endl;
-    cout << v[j] << endl;
+	  std::cout << "Element " << j << " of v:" << std::endl;
+    	  std::cout << v[j] << std::endl;
   }
-  cout << "A temp vector of dimension 3" << endl << vector(3) << endl;
+  std::cout << "A temp vector of dimension 3" << std::endl << vector(3) << std::endl;
   vector k = vector(3);
   k = w;
-  cout << "Assignment of w to k" << endl << k << endl;
-  cout << "Manually set elements of k to elements of v" << endl;
+  std::cout << "Assignment of w to k" << std::endl << k << std::endl;
+  std::cout << "Manually set elements of k to elements of v" << std::endl;
   for (long long j = 0; j < v.get_dimention(); j++)
     k[j] = v[j];
-  cout << k << endl;
+  std::cout << k << std::endl;
 }
 int main() {
   fraction_main();
diff --git a/matrix.hpp b/matrix.hpp
index 6157695..687d95a 100644
--- a/matrix.hpp
+++ b/matrix.hpp
@@ -3,7 +3,6 @@
 #include <iostream>
 #include <sstream>
 #include <string>
-using namespace std;
 class matrix {
 private:
   long long num_entries;
@@ -153,27 +152,27 @@ public:
       return false;
     return *this == this->hermitian_conjugate();
   }
-  friend ostream &operator<<(ostream &os, const matrix &m) {
+  friend std::ostream &operator<<(std::ostream &os, const matrix &m) {
     char last = '\0';
     int longest = 0;
     for (long long i = 0; i < m.num_entries; i++) {
       for (long long j = 0; j < m.entry_dimension; j++) {
-        ostringstream oss;
+        std::ostringstream oss;
         oss << m.entries[i][j];
-        string s = oss.str();
+        std::string s = oss.str();
         if (longest < s.length())
           longest = s.length();
       }
     }
     for (long long i = 0; i < m.num_entries; i++) {
       for (long long j = 0; j < m.entry_dimension; j++) {
-        ostringstream iss;
+        std::ostringstream iss;
         iss << m.entries[i][j];
-        string s = iss.str();
+        std::string s = iss.str();
         int padding = longest - s.length() +1;
-        string symbols[3];
+        std::string symbols[3];
         symbols[0] = "|";
-        ostringstream oss;
+        std::ostringstream oss;
         oss << m.entries[i][j] ;
 	oss << std::setw(padding) << "|";
         symbols[1] = oss.str();
@@ -188,7 +187,7 @@ public:
         }
       }
       if (i != m.num_entries - 1)
-        os << endl << "|";
+        os << std::endl << "|";
     }
     return os;
   }
diff --git a/vector.hpp b/vector.hpp
index 46db71c..5b32640 100644
--- a/vector.hpp
+++ b/vector.hpp
@@ -2,7 +2,6 @@
 #include "cnumber.hpp"
 #include <iomanip>
 #include <iostream>
-using namespace std;
 class matrix;
 class vector {
 private:
@@ -59,23 +58,23 @@ public:
   // outside of the index
   cnumber &operator[](const long long index) { return this->entries[index]; }
 
-  friend ostream &operator<<(ostream &os, const vector &v) {
+  friend std::ostream &operator<<(std::ostream &os, const vector &v) {
     int longest = 0;
     for (long long i = 0; i < v.get_dimention(); i++) {
-      ostringstream oss;
+	    std::ostringstream oss;
       oss << v[i];
-      string s = oss.str();
+      std::string s = oss.str();
       if (longest < s.length())
 	      longest = s.length();
     }
     for (long long i = 0; i < v.get_dimention(); i++) {
-      ostringstream oss;
+	    std::ostringstream oss;
       oss << v[i];
-      string s = oss.str();
+      std::string s = oss.str();
       int padding = longest - s.length() +1;
       os << "|" << v[i] << std::setw(padding) << "|";
       if (i != v.get_dimention() - 1)
-        os << endl;
+        os << std::endl;
     }
     return os;
   }