diff --git a/.gitignore b/.gitignore
index 4b64bc3c..eb96b2ce 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,9 @@
 node_modules
 .tmp
 npm-debug.log
+
+# My addition
+*src/Ch*.exe
+*src/Ch*.out
+*src/Ch*.app
+*src/Ch*.
\ No newline at end of file
diff --git a/src/Ch01/01_02b/CodeDemo.cpp b/src/Ch01/01_02b/CodeDemo.cpp
index c4989f70..b07f36b3 100644
--- a/src/Ch01/01_02b/CodeDemo.cpp
+++ b/src/Ch01/01_02b/CodeDemo.cpp
@@ -1,3 +1,11 @@
 // Learning C++ 
 // Exercise 01_02
 // Hello World, by Eduardo Corpeño 
+
+#include <iostream>
+
+int main(){
+    std::cout << "Hi there!" << std::endl;
+    std::cout << std::endl << std::endl;
+    return (0);
+}
\ No newline at end of file
diff --git a/src/Ch01/01_03/CodeDemo.cpp b/src/Ch01/01_03/CodeDemo.cpp
index 2a89889d..5c7d91df 100644
--- a/src/Ch01/01_03/CodeDemo.cpp
+++ b/src/Ch01/01_03/CodeDemo.cpp
@@ -7,8 +7,9 @@
 
 int main(){
     std::string str;
+    std::cout << "Tell me, what is your name: ";
     std::cin >> str;
-    std::cout << str;
+    std::cout << "Nice to meet you, " << str << "!";
 
     std::cout << std::endl << std::endl;
     return (0);
diff --git a/src/Ch02/02_13/CodeDemo.cpp b/src/Ch02/02_13/CodeDemo.cpp
index 67b9459b..aa7f728d 100644
--- a/src/Ch02/02_13/CodeDemo.cpp
+++ b/src/Ch02/02_13/CodeDemo.cpp
@@ -7,8 +7,11 @@
 int main(){
     int nums[5] = {1,23,32,24,337};
     float result; 
+    int sum;
 
     // Write your code here
+    sum = nums[0] + nums[1] + nums[2] + nums[3] + nums[4];
+    result = sum / 5.0f;
     
     std::cout << "The average is " << result << std::endl;
     
diff --git a/src/Ch03/03_11/records.cpp b/src/Ch03/03_11/records.cpp
index b55b5298..3fae3d1a 100644
--- a/src/Ch03/03_11/records.cpp
+++ b/src/Ch03/03_11/records.cpp
@@ -1 +1,43 @@
-// Write your implementation code here
\ No newline at end of file
+// Write your implementation code here
+#include "records.h"
+
+Student::Student(int the_id, std::string the_name){
+    id = the_id;
+    name = the_name;
+};
+int Student::get_id() const{
+    return id;
+};
+std::string Student::get_name() const{
+    return name;
+};
+
+Course::Course(int the_id, std::string the_name, unsigned char the_credits){
+    id = the_id;
+    name = the_name;
+    credits = the_credits;
+};
+int Course::get_id() const{
+    return id;
+};
+std::string Course::get_name() const{
+    return name;
+};
+int Course::get_credits() const{
+    return credits;
+};
+
+Grade::Grade(int the_sid, int the_cid, char the_grd) {
+    student_id = the_sid;
+    course_id = the_cid;
+    grade = the_grd;
+};
+int Grade::get_student_id() const{
+    return student_id;
+};
+int Grade::get_course_id() const{
+    return course_id;
+};
+char Grade::get_grade() const{
+    return grade;
+};
\ No newline at end of file
diff --git a/src/Ch04/04_05/CodeDemo.cpp b/src/Ch04/04_05/CodeDemo.cpp
index 58e1c596..b474bf0e 100644
--- a/src/Ch04/04_05/CodeDemo.cpp
+++ b/src/Ch04/04_05/CodeDemo.cpp
@@ -9,6 +9,7 @@
 int main(){
     float GPA = 0.0f;
     int id;
+    int total_credits = 0;
     
     std::vector<Student> students = {Student(1, "George P. Burdell"),
                                     Student(2, "Nancy Rhodes")};
@@ -26,9 +27,38 @@ int main(){
 
     // Calculate the GPA for the selected student.
     // Write your code here
+    for (Grade& grade : grades){
+        if (grade.get_student_id() == id){
+            int credit = 0;
+            for (auto course : courses){
+                if (grade.get_course_id() == course.get_id())
+                    credit = course.get_credits();
+            };
+            total_credits += credit;
+            switch (grade.get_grade()){
+                case 'A':
+                    GPA += 4*credit;
+                    break;
+                case 'B':
+                    GPA += 3*credit;
+                    break;
+                case 'C':
+                    GPA += 2*credit;
+                    break;
+                case 'D':
+                    GPA += 1*credit;
+                    break;
+                default:
+                    GPA += 0*credit;
+                    break;
+            };
+        };
+    };
+
+    GPA /= total_credits;
 
     std::string student_str;
-    student_str = students[0].get_name(); // Change this to the selected student's name
+    student_str = students[id-1].get_name(); // Change this to the selected student's name
 
     std::cout << "The GPA for " << student_str << " is " << GPA << std::endl;