diff --git a/README.md b/README.md
index b5df43f..e295421 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@ A package for students of Panimalar Engineering College
 
 ## Modules
 
-### rollno
+## rollno
 
 - isvalid(rollno) => boolean
 - get_dept_code(rollno) => string
@@ -12,6 +12,33 @@ A package for students of Panimalar Engineering College
 - parse(rollno, required) => string (or) int
 - get_year(rollno) => int
 
+## cgpa
+
+### Classes and Methods
+
+- Subject
+- Gpa(Subject)
+- Cgpa(Gpa)
+
+#### Subject 
+This class stores the credit and grade point of a subject.
+- credit
+- grade point
+
+#### Gpa
+
+- addsubject(self, credit: int, grade_point: int)
+- calc(self) -> float
+- display(self) -> None
+- added(self) -> None
+- removesubject(self, index: int) -> None
+  
+#### Cpga
+- calc(self)
+- display(self) -> None
+- added(self) -> None
+- removesemester(self, index: int) -> None
+
 
 ## Details
 
@@ -21,7 +48,7 @@ A package for students of Panimalar Engineering College
 
 Roll Number in Panimalar follows the system (YEAROFJOIN)YYYY-PEC-(DEPT)DD-(ROLLNO)XXXX
 
-eg) 2021PECCB101
+eg - 2021PECCB101
 
 2021 - Year of Join
 PEC - Panimalar Engineering College
diff --git a/pyproject.toml b/pyproject.toml
index eeae459..2126153 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,8 +6,8 @@ build-backend = "setuptools.build_meta"
 name = "panimalar"
 version = "0.3.2"
 authors = [
-    { name="The Coding Society", email="codingsociety@psdc.org.in"},
     { name="aviiciii (Laaveshwaran Parthiban)", email="laavesh1@gmail.com" },
+    { name="The Coding Society", email="codingsociety@psdc.org.in"},
 ]
 description = "A package of function created by and for The Coding Society, Panimalar Engineering College"
 readme = "README.md"
@@ -19,6 +19,8 @@ classifiers = [
 ]
 dependencies = [
     "regex>=2022.10.31",
+    "pytest>=7.2.2",
+    "texttable>=1.6.4",
 ]
 
 
diff --git a/src/cgpa/__init__.py b/src/cgpa/__init__.py
new file mode 100644
index 0000000..cbdbf08
--- /dev/null
+++ b/src/cgpa/__init__.py
@@ -0,0 +1 @@
+from .module import *
\ No newline at end of file
diff --git a/src/cgpa/module.py b/src/cgpa/module.py
new file mode 100644
index 0000000..e097dff
--- /dev/null
+++ b/src/cgpa/module.py
@@ -0,0 +1,290 @@
+# modules
+from texttable import Texttable
+
+class Subject:
+    """
+    This class stores the credit and grade point of a subject.
+    """
+
+    # constructor
+    def __init__(self, credit: int, grade_point: int) -> None:
+
+        # check if the credit and grade point are integers and are not negative
+        if type(credit) != int:
+            raise TypeError("Credit should be an integer.")
+        if type(grade_point) != int:
+            raise TypeError("Grade Point should be an integer.")
+        if credit < 0 or grade_point < 0:
+            raise ValueError("Credit and Grade Point cannot be negative.")
+        
+        
+        self.credit = credit
+        self.grade_point = grade_point
+
+    def __str__(self) -> str:
+        return "Credit: " + str(self.credit) + "\nGrade Point: " + str(self.grade_point)
+
+
+class Gpa(Subject):
+    """
+    This class calculates the GPA of a student.
+    It takes the credit and grade point of each subject as input and returns the GPA.
+    """
+
+    # Class variables
+    # maintains no of subjects added
+    no_of_subjects = 0
+
+    # Constructor
+    def __init__(self) -> None:
+        self.gpa = 0.0
+        self.numerator = 0.0
+        self.denominator = 0.0
+        self.sub=[]
+
+    # Add a subject
+    def addsubject(self, credit: int, grade_point: int) -> None:
+        """
+        addsubject(credit, grade_point)
+        This function adds a subject to the list of subjects.
+        """
+
+
+        # limits on credit and grade point
+
+        if credit > 8:
+            raise ValueError("Credit cannot be greater than 8.")
+        if grade_point > 10:
+            raise ValueError("Grade Point cannot be greater than 10.")
+            
+        
+        # Add subject to the list
+        self.sub.append(Subject(credit, grade_point))
+        self.no_of_subjects += 1
+
+    # Calculate GPA
+    def calc(self) -> float:
+        """
+        calc()
+        This function calculates the GPA of the student.
+        """
+
+        if self.no_of_subjects == 0:
+            raise ValueError("No subjects added yet. Run gpa.addsubject(credit, grade_point) first.")
+            
+        # Check if there is at least one subject with grade point greater than 5
+        for i in range(self.no_of_subjects):
+            greater_than_5 = False
+            if self.sub[i].grade_point > 5:
+                greater_than_5 = True
+            else:
+                pass
+            
+        if not greater_than_5:
+            raise ValueError("No subjects with grade point greater than 5.")
+        
+        # Iterate through the list of subjects and calculate the numerator and denominator
+        for i in range(self.no_of_subjects):
+
+            # Check if the grade point is less than 5
+            if self.sub[i].grade_point < 5:
+                continue
+
+            # Calculate the numerator and denominator
+            self.numerator += self.sub[i].credit * self.sub[i].grade_point
+            self.denominator += self.sub[i].credit
+        
+        # Calculate the GPA with the numerator and denominator
+        self.gpa = self.numerator / self.denominator
+
+        # Check if GPA is valid
+        if self.gpa > 10 and self.gpa < 0:
+            print("GPA is not valid. Please check your inputs.")
+            return
+
+        return self.gpa
+
+    def display(self) -> None:
+        """
+        display()
+        This function displays the number of subjects and the GPA.
+        """
+
+
+        # Check if at least one subject is added
+        if self.no_of_subjects == 0:
+            raise ValueError("No subjects added yet. Run gpa.addsubject(credit, grade_point) first.")
+            
+
+        # Check if GPA is calculated
+        if self.gpa == 0.0:
+            raise ValueError("No GPA calculated yet. Run gpa.calc() first.")
+            
+        
+        # Display the number of subjects and the GPA
+        print("No of subjects: ", self.no_of_subjects)
+        print("GPA: ", self.gpa)
+
+    def added(self) -> None:
+        """
+        added()
+        This function displays the subjects added.
+        """
+        
+        table = Texttable()
+
+        table.header(["No.", "Credits", "Grade Points"])
+        table.set_cols_dtype(['i', 'i', 'i'])
+        table.set_cols_align(['r', 'r', 'r'])
+
+        for i in range(self.no_of_subjects):
+            table.add_row([i+1, self.sub[i].credit, self.sub[i].grade_point])
+
+        table.set_deco(Texttable.HEADER)
+        print('Subjects added:')
+        print(table.draw())
+        
+    def removesubject(self, index: int) -> None:
+        """
+        removesubject(index)
+        Index values: 1-n
+        This function removes a subject from the list of subjects.
+        """
+        index = index-1
+        # Check if the index is valid
+        if index > self.no_of_subjects or index < 0:
+            raise ValueError(f"Index out of range. Input Index: {index+1} Index Region: 0 to {self.no_of_subjects}")
+            
+        
+        # Remove the subject from the list
+        removed = self.sub.pop(index-1)
+        self.no_of_subjects -= 1
+        print(f'Subject {index + 1} {removed.credit, removed.grade_point} removed successfully.')
+
+    def __repr__(self) -> str:
+        return "GPA Calculator"
+    
+    def __str__(self) -> str:
+
+        if self.no_of_subjects == 0:
+            return "No subjects added yet. Run gpa.addsubject(credit, grade_point) first."
+        
+        return "No of subjects: " + str(self.no_of_subjects) + "GPA: " + str(self.gpa)
+    
+
+class Cgpa(Gpa):
+    """
+    This class calculates the CGPA of a student.
+    It takes the GPA of each semester as input and returns the CGPA.
+    """
+
+    # Constructor
+    def __init__(self):
+        self.cgpa = 0.0
+        self.total_numerator = 0.0
+        self.total_denominator = 0
+        self.semester = []
+    
+
+    # Add a semester gpa
+    def addsemester(self, gpa: Gpa) -> None:
+        """
+        addsemester(gpa)
+        This function adds a semester gpa to the list of semester gpa.
+        """
+
+        # Check if the input is of type Gpa else raise an error
+        if not isinstance(gpa, Gpa):
+            raise TypeError("Input must be of type Gpa.")
+
+        # Check if the gpa is calculatable else raise an error
+        if gpa.no_of_subjects <= 0:
+            raise ValueError("No subjects added yet. Run gpa.addsubject(credit, grade_point) first.")
+        
+
+
+        gpa.calc()
+        self.semester.append(gpa)
+            
+        
+    # Calculate CGPA
+    def calc(self) -> float:
+        """
+        calc()
+        This function calculates the CGPA of the student.
+        """
+
+        if len(self.semester) == 0:
+            raise ValueError("No semesters added yet. Run cgpa.addsemester(gpa) first.")
+        
+        # Iterate through the list of semester gpa and calculate the numerator and denominator
+        for i in range(len(self.semester)):
+            self.total_numerator += self.semester[i].numerator
+            self.total_denominator += self.semester[i].denominator
+
+        # Calculate the CGPA with the numerator and denominator
+        self.cgpa = self.total_numerator / self.total_denominator
+
+        # Check if CGPA is valid
+        if self.cgpa > 10 and self.cgpa < 0:
+            print("CGPA is not valid. Please check your inputs.")
+            return
+
+        return self.cgpa
+    
+    # Display CGPA
+    def display(self) -> None:
+        """
+        display()
+        This function displays the number of semesters and the CGPA.
+        """
+
+        if len(self.semester) == 0:
+            raise ValueError("No semesters added yet. Run cgpa.addsemester(gpa) first.")
+        if self.cgpa == 0.0:
+            raise ValueError("No CGPA calculated yet. Run cgpa.calc() first.")
+        
+        print("No of semesters: ", len(self.semester))
+        print("CGPA: ", self.cgpa)
+    
+    def added(self) -> None:
+        """
+        added()
+        This function displays the semesters added.
+        """
+        
+        table = Texttable()
+
+        table.header(["No.", "GPA", "\u03A3 GP*C", "\u03A3 Credits"])
+        table.set_cols_dtype(['i', 'f', 'i', 'i'])
+        table.set_cols_align(['r', 'r', 'r', 'r'])
+
+        for i in range(len(self.semester)):
+            table.add_row([i+1, self.semester[i].gpa, self.semester[i].numerator, self.semester[i].denominator])
+
+        table.set_deco(Texttable.HEADER)
+        print('Semesters added:')
+        print(table.draw())
+
+    def removesemester(self, index: int) -> None:
+        """
+        removesemester(index)
+        Index values: 1-n
+        This function removes a semester from the list of semesters.
+        """
+        index = index-1
+        # Check if the index is valid
+        if index > len(self.semester) or index < 0:
+            raise ValueError(f"Index out of range. Input Index: {index+1} Index Region: 0 to {len(self.semester)}")
+            
+        
+        # Remove the semester from the list
+        removed = self.semester.pop(index-1)
+        print(f'Semester {index+1} {removed.gpa, removed.numerator, removed.denominator} removed successfully.')
+
+    def __repr__(self) -> str:
+        return "CGPA Calculator"
+
+    def __str__(self) -> str:
+        return "No of semesters: " + str(len(self.semester)) + "CGPA: " + str(self.cgpa)
+        
diff --git a/tests/test_cgpa.py b/tests/test_cgpa.py
new file mode 100644
index 0000000..d7829d2
--- /dev/null
+++ b/tests/test_cgpa.py
@@ -0,0 +1,415 @@
+import pytest
+from src.cgpa import *
+
+
+# Subject class test cases
+
+def test_subject_class():
+    # Test if the subject class is defined
+    obj = Subject(4, 10)
+    assert obj.credit == 4
+    assert obj.grade_point == 10
+
+    obj = Subject(3, 9)
+    assert obj.credit == 3
+    assert obj.grade_point == 9
+
+    # raise an error if the credit is not an integer
+    with pytest.raises(TypeError):
+        obj = Subject(3.5, 9)
+    with pytest.raises(TypeError):
+        obj = Subject('three', 9)
+    with pytest.raises(TypeError):
+        obj = Subject(True, 9)
+
+    # raise an error if the grade_point is not an integer
+    with pytest.raises(TypeError):
+        obj = Subject(3, 9.5)
+    with pytest.raises(TypeError):
+        obj = Subject(3, 'nine')
+    with pytest.raises(TypeError):
+        obj = Subject(3, True)
+
+    # raise an error if the credit and grade point is not negative
+    with pytest.raises(ValueError):
+        obj = Subject(-3, 9)
+    with pytest.raises(ValueError):
+        obj = Subject(3, -9)
+    with pytest.raises(ValueError):
+        obj = Subject(-3, -9)
+    
+# GPA class test cases
+
+# addsubject function test cases
+
+def test_addsubject():
+    # create an object of the gpa class
+    obj = Gpa()
+
+    # Test if the addsubject function is defined
+    obj.addsubject(4, 10)
+    assert obj.no_of_subjects == 1
+    assert obj.sub[0].credit == 4
+    assert obj.sub[0].grade_point == 10
+
+    obj.addsubject(3, 9)
+    assert obj.no_of_subjects == 2
+    assert obj.sub[1].credit == 3
+    assert obj.sub[1].grade_point == 9
+
+
+def test_invalid_credit():
+    with pytest.raises(TypeError):
+        obj = Subject(3.5, 9)
+    with pytest.raises(TypeError):
+        obj = Subject('three', 9)
+    with pytest.raises(TypeError):
+        obj = Subject(True, 9)
+
+
+def test_invalid_grade_point():
+    with pytest.raises(TypeError):
+        obj = Subject(3, 9.5)
+    with pytest.raises(TypeError):
+        obj = Subject(3, 'nine')
+    with pytest.raises(TypeError):
+        obj = Subject(3, True)
+
+
+def test_invalid_credit_and_grade_point():
+    obj = Gpa()
+    # raise an error if the credit and grade point is not negative
+    with pytest.raises(ValueError):
+        obj.addsubject(-3, 9)
+    with pytest.raises(ValueError):
+        obj.addsubject(3, -9)
+    with pytest.raises(ValueError):
+        obj.addsubject(-3, -9)
+
+
+def test_credit_greater_than_8():
+    obj = Gpa()
+
+    # raise an error if the credit is greater than 8
+    with pytest.raises(ValueError):
+        obj.addsubject(9, 9)
+    with pytest.raises(ValueError):
+        obj.addsubject(13, 9)
+
+
+def test_grade_point_greater_than_10():
+    obj = Gpa()
+
+    # raise an error if the grade point is greater than 10
+    with pytest.raises(ValueError):
+        obj.addsubject(3, 11)
+    with pytest.raises(ValueError):
+        obj.addsubject(3, 15)
+
+# calc function test cases
+
+def test_calc_1():
+    obj = Gpa()
+
+    # Test if the calc function is defined
+    obj.addsubject(4, 10)
+    obj.addsubject(3, 9)
+    obj.addsubject(3, 8)
+    obj.addsubject(2, 7)
+    obj.addsubject(2, 8)
+    obj.addsubject(1, 9)
+    obj.addsubject(3, 9)
+    obj.addsubject(2, 3)
+    obj.calc()
+    
+    assert obj.no_of_subjects == 8
+
+    assert obj.gpa == 8.722222222222221
+
+
+def test_calc_2():
+    obj = Gpa()
+
+    # Test if the calc function is defined
+    obj.addsubject(4, 10)
+    obj.addsubject(3, 10)
+    obj.addsubject(3, 10)
+    obj.addsubject(2, 10)
+    obj.addsubject(2, 10)
+    obj.addsubject(1, 10)
+    obj.addsubject(3, 10)
+    obj.addsubject(2, 10)
+    obj.addsubject(2, 10)
+    obj.calc()
+
+    assert obj.gpa == 10
+
+
+def test_calc_3():
+    obj = Gpa()
+
+    # Test if the calc function is defined
+    obj.addsubject(4, 7)
+    obj.addsubject(3, 7)
+    obj.addsubject(3, 7)
+    obj.addsubject(2, 7)
+    obj.addsubject(2, 7)
+    obj.addsubject(1, 7)
+    obj.addsubject(3, 7)
+    obj.addsubject(2, 7)
+    obj.addsubject(2, 7)
+    obj.calc()
+
+    assert obj.gpa == 7
+
+
+def test_calc_4():
+    obj = Gpa()
+
+    # Test if the calc function is defined
+    obj.addsubject(2, 8)
+    obj.addsubject(3, 8)
+    obj.addsubject(3, 7)
+    obj.addsubject(4, 8)
+    obj.addsubject(2, 10)
+    obj.addsubject(4, 9)
+    obj.addsubject(4, 9)
+    obj.addsubject(3, 8)
+    obj.calc()
+
+    assert obj.gpa == 8.36
+
+
+def test_calc_with_no_subjects():
+    obj = Gpa()
+
+    # Test if the calc function is defined
+    with pytest.raises(ValueError):
+        obj.calc()
+
+    assert obj.gpa == 0.0
+
+# display function test cases
+
+def test_display(capsys):
+    obj = Gpa()
+
+    # Test if the display function is defined
+    obj.addsubject(4, 10)
+    obj.addsubject(3, 9)
+    obj.addsubject(3, 8)
+    obj.addsubject(2, 7)
+    obj.addsubject(2, 7)
+    obj.addsubject(1, 9)
+    obj.addsubject(3, 8)
+    obj.addsubject(2, 3)
+
+    # calculate and call the display function
+    obj.calc()
+    obj.display()
+    
+    # capture the output(prints)
+    captured = capsys.readouterr()
+
+    # check if the output is correct
+    assert captured.out == "No of subjects:  8\nGPA:  8.444444444444445\n"
+
+
+def test_display_with_no_subjects():
+    obj = Gpa()
+
+    # Test if the display function is defined
+    with pytest.raises(ValueError):
+        obj.display()
+    
+    assert obj.gpa == 0.0
+
+
+def test_display_with_no_calc():
+    obj = Gpa()
+
+    # Test if the display function is defined
+    obj.addsubject(4, 10)
+    obj.addsubject(3, 9)
+    obj.addsubject(3, 8)
+    obj.addsubject(2, 7)
+    obj.addsubject(2, 7)
+    obj.addsubject(1, 9)
+    obj.addsubject(3, 8)
+    obj.addsubject(2, 3)
+
+    with pytest.raises(ValueError):
+        obj.display()
+    
+    assert obj.gpa == 0.0
+
+
+# gpa class overall test cases
+def test_gpa_class(capsys):
+    obj = Gpa()
+
+    # add subjects
+    credits = [2, 3, 3, 4, 2, 4, 4, 3]
+    grade_points = [8, 8, 7, 8, 10, 9, 9, 8]
+
+    for i in range(len(credits)):
+        obj.addsubject(credits[i], grade_points[i])
+
+    # check if the number of subjects is correct
+    assert obj.no_of_subjects == 8
+
+    # check if subjects are added to list
+    assert len(obj.sub) == 8
+
+    # check if subjects are added correctly
+    for i in range(len(obj.sub)):
+        assert obj.sub[i].credit == credits[i]
+        assert obj.sub[i].grade_point == grade_points[i]
+
+    # calculate
+    obj.calc()
+
+    # display
+    obj.display()
+
+    # capture the output(prints)
+    captured = capsys.readouterr()
+
+    # check if the output is correct
+    assert captured.out == "No of subjects:  8\nGPA:  8.36\n"
+
+    # check if the gpa is correct
+    assert obj.gpa == 8.36
+
+
+# cgpa class test cases
+
+
+# addsemester function test cases
+def test_addsemester():
+    obj = Cgpa()
+
+    gpa_obj = Gpa()
+
+    # add subjects
+    credits = [2, 3, 3, 4, 2, 4, 4, 3]
+    grade_points = [8, 8, 7, 8, 10, 9, 9, 8]
+
+    for i in range(len(credits)):
+        gpa_obj.addsubject(credits[i], grade_points[i])
+
+
+    # Test if the addsemester function is defined
+    obj.addsemester(gpa_obj)
+
+    # check if the semester is added to the list
+    assert len(obj.semester) == 1
+
+    # check if the semester is added correctly
+    assert obj.semester[0].gpa == 8.36
+
+def test_invalid_addsemester():
+    obj = Cgpa()
+
+    # Test if the addsemester function is defined
+    with pytest.raises(TypeError):
+        obj.addsemester(-1)
+
+    with pytest.raises(TypeError):
+        obj.addsemester(15)
+
+    with pytest.raises(TypeError):
+        obj.addsemester('hello')
+
+    with pytest.raises(TypeError):
+        obj.addsemester(3.14)
+
+def test_addsemester_with_no_subjects():
+    obj = Cgpa()
+
+    gpa_obj = Gpa()
+
+    # Test if the addsemester function is defined
+    with pytest.raises(ValueError):
+        obj.addsemester(gpa_obj)
+
+    assert len(obj.semester) == 0
+
+def test_addsemester_with_fail_gradepoints():
+    obj = Cgpa()
+
+    gpa_obj = Gpa()
+
+    # add subjects
+    credits = [2, 3, 3, 4, 2, 4, 4, 3]
+    grade_points = [1, 2, 4, 2, 1, 2, 4, 2]
+
+    for i in range(len(credits)):
+        gpa_obj.addsubject(credits[i], grade_points[i])
+    
+    # Test if the addsemester function is defined
+    with pytest.raises(ValueError):
+        obj.addsemester(gpa_obj)
+
+    assert len(obj.semester) == 0
+
+def test_addsemester_multiple_semesters():
+    obj = Cgpa()
+
+    gpa_obj1 = Gpa()
+    gpa_obj2 = Gpa()
+    gpa_obj3 = Gpa()
+
+    # sem 1
+    credits = [2, 3, 3, 4, 2, 4, 4, 3]
+    grade_points = [8, 8, 7, 8, 10, 9, 9, 8]
+
+    for i in range(len(credits)):
+        gpa_obj1.addsubject(credits[i], grade_points[i])
+
+    # sem 2
+    credits = [2, 4, 3, 4, 2, 2, 4, 2]
+    grade_points = [7, 8, 7, 8, 10, 6, 9, 8]
+
+    for i in range(len(credits)):
+        gpa_obj2.addsubject(credits[i], grade_points[i])
+
+    # sem 3
+    credits = [2, 3, 4, 3, 2, 3, 4, 3]
+    grade_points = [10, 8, 7, 8, 7, 9, 7, 8]
+
+    for i in range(len(credits)):
+        gpa_obj3.addsubject(credits[i], grade_points[i])
+
+    # Test if the addsemester function is defined
+    obj.addsemester(gpa_obj1)
+    obj.addsemester(gpa_obj2)
+    obj.addsemester(gpa_obj3)
+
+    assert len(obj.semester) == 3
+
+    assert obj.semester[0].gpa == 8.36
+    assert obj.semester[1].gpa == 7.956521739130435
+    assert obj.semester[2].gpa == 7.875
+
+
+
+# calc function test cases
+def test_cgpa_calc():
+    obj = Cgpa()
+
+    gpa_obj = Gpa()
+
+    # add subjects
+    credits = [2, 3, 3, 4, 2, 4, 4, 3]
+    grade_points = [8, 8, 7, 8, 10, 9, 9, 8]
+
+    for i in range(len(credits)):
+        gpa_obj.addsubject(credits[i], grade_points[i])
+
+    obj.addsemester(gpa_obj)
+
+    # Test if the calc function is defined
+    obj.calc()
+
+    assert obj.cgpa == 8.36
\ No newline at end of file
diff --git a/tests/test_module.py b/tests/test_rollno.py
similarity index 100%
rename from tests/test_module.py
rename to tests/test_rollno.py