diff --git a/30 Days of Code/Day 04/Class vs. Instance.cpp b/30 Days of Code/Day 04/Class vs. Instance.cpp
new file mode 100644
index 0000000..98340b0
--- /dev/null
+++ b/30 Days of Code/Day 04/Class vs. Instance.cpp	
@@ -0,0 +1,30 @@
+class Person{
+    public:
+        int age;
+        Person(int initialAge);
+        void amIOld();
+        void yearPasses();
+};
+
+    Person::Person(int initialAge){
+      
+      //code to run some checks on initialAge
+        if(initialAge<0) {cout<<"Age is not valid, setting age to 0."<<endl;age=0;}
+        else age = initialAge;
+
+    }
+
+    void Person::amIOld(){
+      
+      // code to determine if this person's age is old and print the correct statement:
+        if(this->age<13) cout<<"You are young."<<endl;
+        else if(this->age>=18) cout<<"You are old."<<endl;
+        else cout<<"You are a teenager."<<endl;
+
+    }
+
+    void Person::yearPasses(){
+      
+      // Increment this person's age by 1.
+        age++;
+    }