diff --git a/26 Dictionaries/exercise-01.py b/26 Dictionaries/exercise-01.py
index e69de29..d7f2fef 100644
--- a/26 Dictionaries/exercise-01.py	
+++ b/26 Dictionaries/exercise-01.py	
@@ -0,0 +1,27 @@
+animals = {
+    "cat": "meow",
+    "dog": "woof",
+    "bird": "chirp",
+    "fish": "swim",
+    "snake": "slither",
+    "horse": "neigh",
+}
+
+score = [0, 0] # correct, total
+
+run = True
+
+while run:
+    for i in animals:
+        print(f"What animal goes {animals[i]}?")
+        answer = input("> ")
+        
+        if answer.lower().strip() == i.lower():
+            print(f"Correct! {i} goes {animals[i]}.")
+            score[0] += 1
+        score[1] += 1
+    print(f"Score: {round(score[0]/score[1]*100)}%")
+    
+    if not round(score[0]/score[1]*100) < 60:
+        run = True
+        score = [0, 0]
\ No newline at end of file
diff --git a/27 Nested Dictionary/exercise-01.py b/27 Nested Dictionary/exercise-01.py
new file mode 100644
index 0000000..3e26ef5
--- /dev/null
+++ b/27 Nested Dictionary/exercise-01.py	
@@ -0,0 +1,59 @@
+student_names = {}
+
+# data structure
+# student_names = {
+#     "john": {
+#       "HW1": 15
+#       "HW2": 20
+#     },
+#     "jane": {
+#       "HW1": 10
+#       "HW2": 15
+#     }
+# }
+
+def get_student_name():
+    while True:
+        student_name = input("Enter student name: ").strip().lower()
+        if student_name == "!break":
+            return None
+        elif student_name in student_names:
+            return student_name
+        else:
+            return student_name
+        
+def update_data(student_name, hw, score):
+    if student_name not in student_names:
+        student_names[student_name] = {}
+    
+    if hw not in student_names[student_name]:
+        student_names[student_name][hw] = score
+    else:
+        print("HW already exists.")
+        
+def display_data():
+    for student in student_names:
+        print(f"{student}:")
+        for hw in student_names[student]:
+            print(f"  {hw}: {student_names[student][hw]}")
+
+def main():
+    Run = True
+    
+    while Run:
+        student_name = get_student_name()
+        
+        if student_name is None:
+            Run = False
+            print("Outputting data...")
+            break
+        
+        hw = input("Enter homework name: ").strip().lower()
+        
+        score = int(input("Enter score: "))
+        update_data(student_name, hw, score)
+        
+    display_data()
+    
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/27 Nested Dictionary/task.png b/27 Nested Dictionary/task.png
new file mode 100644
index 0000000..f13b3cd
Binary files /dev/null and b/27 Nested Dictionary/task.png differ
diff --git a/28 File handling/exercise-01.py b/28 File handling/exercise-01.py
new file mode 100644
index 0000000..3b36e40
--- /dev/null
+++ b/28 File handling/exercise-01.py	
@@ -0,0 +1,37 @@
+students = [
+    "john",
+    "jane",
+    "bob",
+    "alice",
+    "charlie",
+    "david",
+    "emily",
+    "frank",
+    "grace",
+    "harry",
+    "isabella",
+    "jessica",
+]
+
+with open("students.txt", "w") as f:
+    for student in students:
+        f.write(f"{student}\n")
+
+students = []
+
+with open("students.txt", "r") as f:
+    for line in f:
+        students.append(line.strip())
+
+print("Unsorted: ")
+print(students)
+
+students.sort()
+print("")
+
+print("Sorted: ")
+print(students)
+
+with open("students.txt", "w") as f:
+    for student in students:
+        f.write(f"{student}\n")
\ No newline at end of file
diff --git a/28 File handling/exercise-02.py b/28 File handling/exercise-02.py
new file mode 100644
index 0000000..dd3cc7c
--- /dev/null
+++ b/28 File handling/exercise-02.py	
@@ -0,0 +1,13 @@
+groceries = []
+
+with open("shopping.txt", "r") as f:
+    for line in f:
+        groceries.append(line.strip())
+
+print(groceries)
+
+for i in range(3):
+    item = input("Enter item to add to shopping list: ").strip().lower()
+    groceries.append(item)
+    
+print(groceries)
\ No newline at end of file
diff --git a/28 File handling/task.png b/28 File handling/task.png
new file mode 100644
index 0000000..4a13482
Binary files /dev/null and b/28 File handling/task.png differ
diff --git a/29 Validation/exercise-01.py b/29 Validation/exercise-01.py
new file mode 100644
index 0000000..64fd29c
--- /dev/null
+++ b/29 Validation/exercise-01.py	
@@ -0,0 +1,42 @@
+def get_score():
+    """ asks for test score """
+    collect = True
+    
+    while collect:
+        test_score = input("Enter test score: ").strip()
+        if test_score.isnumeric():
+            test_score = int(test_score)
+            if test_score >= 0 and test_score <= 100:
+                collect = False
+            else:
+                print("Invalid input. Please enter a number between 0 and 100.")
+        else:
+            print("Invalid input. Please enter a number.")
+    
+    return test_score
+
+def main():
+    """ runs all functions """
+    test_score = int(get_score())
+    
+    print("These are the GSCE grade boundaries:")
+    if test_score >= 90:
+        print("Your grade is 9")
+    elif test_score >= 80:
+        print("Your grade is 8")
+    elif test_score >= 70:
+        print("Your grade is 7")
+    elif test_score >= 60:
+        print("Your grade is 6")
+    elif test_score >= 50:
+        print("Your grade is 5")
+    elif test_score >= 40:
+        print("Your grade is 4")
+    elif test_score >= 30:
+        print("Your grade is 3")
+    elif test_score >= 20:
+        print("Your grade is 2")
+    else:
+        print("Your grade is 1")
+        
+main()
\ No newline at end of file
diff --git a/29 Validation/task.png b/29 Validation/task.png
new file mode 100644
index 0000000..994c140
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diff --git a/30 Authentication/exercise-01.py b/30 Authentication/exercise-01.py
new file mode 100644
index 0000000..a1be7bb
--- /dev/null
+++ b/30 Authentication/exercise-01.py	
@@ -0,0 +1,32 @@
+# 2d table of users and passwords
+
+users = [
+    ["john", "password"],
+    ["jane", "1234"],
+    ["alice", "31234"],
+    ["charlie", "1863"],
+    ["david", "3958"],
+]
+
+def login():
+    for i in range(3):
+        username = input("Enter username: ").strip().lower()
+        password = input("Enter password: ").strip()
+        
+        for user in users:
+            if user[0] == username and user[1] == password:
+                return True
+                break
+        
+    return False
+
+def main():
+    log = login()
+    
+    if log:
+        print("Login successful!")
+    else:
+        print("Invalid username or password.")
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/30 Authentication/exercise-02.py b/30 Authentication/exercise-02.py
new file mode 100644
index 0000000..e5bb045
--- /dev/null
+++ b/30 Authentication/exercise-02.py	
@@ -0,0 +1,63 @@
+users = {
+    "john": "password",
+    "jane": "1234",
+    "alice": "31234",
+    "charlie": "1863",
+    "david": "3958",
+}
+
+def login():
+    for i in range(3):
+        username = input("Enter username: ").strip().lower()
+        password = input("Enter password: ").strip()
+        
+        if username in users and users[username] == password:
+            return True
+    
+    return False
+
+def add_user():
+    username = input("Enter new username: ").strip().lower()
+    if username in users:
+        print(f"User '{username}' already exists.")
+        return
+    
+    password = input("Enter password: ").strip()
+    users[username] = password
+    print(f"User '{username}' added successfully!")
+
+def remove_user():
+    username = input("Enter username to remove: ").strip().lower()
+    if username not in users:
+        print(f"User '{username}' not found.")
+        return
+    
+    del users[username]
+    print(f"User '{username}' removed successfully!")
+
+def list_users():
+    print("Current users:", list(users.keys()))
+
+def main():
+    while True:
+        print("\n1. Login\n2. Add user\n3. Remove user\n4. List users\n5. Exit")
+        choice = input("Enter choice: ").strip()
+        
+        if choice == '1':
+            if login():
+                print("Login successful!")
+            else:
+                print("Invalid username or password.")
+        elif choice == '2':
+            add_user()
+        elif choice == '3':
+            remove_user()
+        elif choice == '4':
+            list_users()
+        elif choice == '5':
+            break
+        else:
+            print("Invalid choice.")
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/30 Authentication/task.png b/30 Authentication/task.png
new file mode 100644
index 0000000..9950d69
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