diff --git a/main.py b/main.py
new file mode 100644
index 0000000..c238362
--- /dev/null
+++ b/main.py
@@ -0,0 +1,25 @@
+import subject
+import user_IO
+
+subjects = []
+try:
+    while True:
+        user_input = user_IO.user_input()
+        if user_input[0] == "input":
+            if user_input[1] == "grade":
+                subject_edit = subject.get_subject(subjects, user_input[2])
+                if subject_edit:
+                    subject_edit.add_grade(user_input[3], subject.Grade(user_input[4], user_input[5]))
+            elif user_input[1] == "category":
+                subject_edit = subject.get_subject(subjects, user_input[2])
+                if subject_edit:
+                    subject_edit.add_grade_category(user_input[3], user_input[4])
+            elif user_input[1] == "subject":
+                subjects.append(subject.Subject(user_input[2], user_input[3], user_input[4]))
+        elif user_input[0] == "output":
+            subject_get = subject.get_subject(subjects, user_input[1])
+            user_IO.user_output(subject_get.return_average_subject)
+    raise SystemError
+
+except Exception as e:
+    print('ERROR' + str(e))
\ No newline at end of file
diff --git a/subject.py b/subject.py
index dda4c0d..2c8c6eb 100644
--- a/subject.py
+++ b/subject.py
@@ -37,3 +37,10 @@ class Grade:
         self.grade = grade
         self.name = name
         self.date = date
+
+
+def get_subject(liste, name):
+    for subject in liste:
+        if subject.name == name:
+            return subject
+    return None
diff --git a/user_IO.py b/user_IO.py
index 4fa37a9..f399d07 100644
--- a/user_IO.py
+++ b/user_IO.py
@@ -9,15 +9,30 @@ def user_input():
         user_add = input()
         if user_add == "subject":
             subject = input("Which subject do you want to add? \n")
-            return "input", subject
+            main_subject = input("Is this subject a main subject (Hauptfach)[y/n]? \n")
+            if main_subject == 'y':
+                main_subject = True
+            elif main_subject == 'n':
+                main_subject = False
+            oral_exam = input("Will there be an oral exam in this subject [y/n]? \n")
+            if oral_exam == 'y':
+                oral_exam = True
+            elif oral_exam == 'n':
+                oral_exam = False
+            return "input", "subject", subject, main_subject, oral_exam
         elif user_add == "category":
             subject = input("To which subject do you want to add the category? \n")
             category = input("Which category do you want to add? \n")
             rating = float(input("Rating? \n"))
-            return "input", subject, category, rating
+            return "input", "category", subject, category, rating
         elif user_add == "grade":
             subject = input("To which subject do you want to add the grade? \n")
             category = input("To which category do you want to add it? \n")
             grade = input("Grade? \n")
             grade_name = input("What's the name of the grade? \n")
-            return "input", subject, category, grade, grade_name
+            return "input", "grade", subject, category, grade, grade_name
+
+
+def user_output(i):
+    # just filled with some standard output, has to be filled further
+    print(i)
\ No newline at end of file