diff --git a/boot.py b/boot.py
index 65ff06d..8f3adbc 100644
--- a/boot.py
+++ b/boot.py
@@ -1,12 +1,13 @@
 import os
 import importlib
 import pkgutil
+import types
 
 COMMANDS_PACKAGE = 'commands'
 
 
-def load_commands():
-    commands = {}
+def load_commands() -> dict[str, types.ModuleType]:
+    commands: dict[str, types.ModuleType] = {}
     package = importlib.import_module(COMMANDS_PACKAGE)
     for loader, name, is_pkg in pkgutil.iter_modules(package.__path__):
         if name.startswith('_'):
@@ -17,7 +18,7 @@ def load_commands():
     return commands
 
 
-def main():
+def main() -> None:
     os.system('cls' if os.name == 'nt' else 'clear')
     print('Booting PyOS...')
     commands = load_commands()
diff --git a/commands/cat.py b/commands/cat.py
index a210f17..d57f0ee 100644
--- a/commands/cat.py
+++ b/commands/cat.py
@@ -1,13 +1,14 @@
-# WAFCAT :heart:
+import typing
 
-help = "Print file contents. Usage: cat <file>"
+command_help: str = 'Print file contents. Usage: cat <file>'
 
-def run(args):
+
+def run(args: typing.Any) -> None:
     if not args:
-        print("Usage: cat <file>")
+        print('Usage: cat <file>')
         return
     try:
         with open(args[0], 'r') as f:
             print(f.read())
     except Exception as e:
-        print(f"Error: {e}")
\ No newline at end of file
+        print(f'Error: {e}')
diff --git a/commands/cd.py b/commands/cd.py
index edeac91..bcee7c7 100644
--- a/commands/cd.py
+++ b/commands/cd.py
@@ -1,11 +1,14 @@
-help = "Change directory. Usage: cd <dir>"
+import typing
 
-def run(args):
+command_help: str = 'Change directory. Usage: cd <dir>'
+
+
+def run(args: typing.Any) -> None:
     import os
     if not args:
-        print("Usage: cd <directory>")
+        print('Usage: cd <directory>')
         return
     try:
         os.chdir(args[0])
     except Exception as e:
-        print(f"Error: {e}")
\ No newline at end of file
+        print(f'Error: {e}')
diff --git a/commands/clear.py b/commands/clear.py
index 81a82cb..976c908 100644
--- a/commands/clear.py
+++ b/commands/clear.py
@@ -1,5 +1,8 @@
-help = "Clear the screen."
+import typing
 
-def run(args):
+command_help: str = 'Clear the screen.'
+
+
+def run(_args: typing.Any) -> None:
     import os
-    os.system('cls' if os.name == 'nt' else 'clear')
\ No newline at end of file
+    os.system('cls' if os.name == 'nt' else 'clear')
diff --git a/commands/del.py b/commands/del.py
index 6dcd741..a02e5bc 100644
--- a/commands/del.py
+++ b/commands/del.py
@@ -1,18 +1,21 @@
-help = "Delete file or directory. Usage: del <file/dir>"
+import typing
 
-def run(args):
+command_help: str = 'Delete file or directory. Usage: del <file/dir>'
+
+
+def run(args: typing.Any) -> None:
     import os
     if not args:
-        print("Usage: del <file/dir>")
+        print('Usage: del <file/dir>')
         return
     target = args[0]
     if os.path.isdir(target):
         try:
             os.rmdir(target)
         except Exception as e:
-            print(f"Error: {e}")
+            print(f'Error: {e}')
     else:
         try:
             os.remove(target)
         except Exception as e:
-            print(f"Error: {e}")
\ No newline at end of file
+            print(f'Error: {e}')
diff --git a/commands/exit.py b/commands/exit.py
index b7543ca..e09a0dd 100644
--- a/commands/exit.py
+++ b/commands/exit.py
@@ -1,5 +1,8 @@
-help = "Exit PyOS."
+import typing
 
-def run(args):
-    print("Goodbye!")
-    exit(0)
\ No newline at end of file
+command_help: str = 'Exit PyOS.'
+
+
+def run(_args: typing.Any) -> None:
+    print('Goodbye!')
+    exit(0)
diff --git a/commands/help.py b/commands/help.py
index b35a63b..5ce2a5d 100644
--- a/commands/help.py
+++ b/commands/help.py
@@ -1,12 +1,13 @@
-import os
+import typing
 
-help = """Show help for all commands."""
+command_help: str = 'Show help for all commands.'
 
-def run(args):
+
+def run(_args: typing.Any) -> None:
     from boot import load_commands
     commands = load_commands()
-    print("Available commands:")
+    print('Available commands:')
     for name in sorted(commands):
         mod = commands[name]
-        doc = getattr(mod, "help", "")
-        print(f"  {name:<10} {doc}")
\ No newline at end of file
+        doc = getattr(mod, 'command_help', '')
+        print(f'  {name:<10} {doc}')
diff --git a/commands/ls.py b/commands/ls.py
index 5362f56..6a8044d 100644
--- a/commands/ls.py
+++ b/commands/ls.py
@@ -1,6 +1,9 @@
-help = "List files in current directory."
+import typing
 
-def run(args):
+command_help: str = 'List files in current directory.'
+
+
+def run(_args: typing.Any) -> None:
     import os
     for f in os.listdir():
-        print(f)
\ No newline at end of file
+        print(f)
diff --git a/commands/mkdir.py b/commands/mkdir.py
index 3292439..2656e8a 100644
--- a/commands/mkdir.py
+++ b/commands/mkdir.py
@@ -1,11 +1,14 @@
-help = "Create a directory. Usage: mkdir <dir>"
+import typing
 
-def run(args):
+command_help: str = 'Create a directory. Usage: mkdir <dir>'
+
+
+def run(args: typing.Any) -> None:
     import os
     if not args:
-        print("Usage: mkdir <dir>")
+        print('Usage: mkdir <dir>')
         return
     try:
         os.mkdir(args[0])
     except Exception as e:
-        print(f"Error: {e}")
\ No newline at end of file
+        print(f'Error: {e}')
diff --git a/commands/mkfil.py b/commands/mkfil.py
index b9518b5..07ba5ea 100644
--- a/commands/mkfil.py
+++ b/commands/mkfil.py
@@ -1,11 +1,13 @@
-help = "Create an empty file. Usage: mkfil <file>"
+import typing
 
+command_help: str = 'Create an empty file. Usage: mkfil <file>'
 
-def run(args):
+
+def run(args: typing.Any) -> None:
     if not args:
-        print("Usage: mkfil <file>")
+        print('Usage: mkfil <file>')
         return
     try:
         open(args[0], 'a').close()
     except Exception as e:
-        print(f"Error: {e}")
+        print(f'Error: {e}')
diff --git a/commands/printdir.py b/commands/printdir.py
index 0f7f281..593e255 100644
--- a/commands/printdir.py
+++ b/commands/printdir.py
@@ -1,5 +1,8 @@
-help = "Print working directory."
+import typing
 
-def run(args):
+command_help: str = 'Print working directory.'
+
+
+def run(_args: typing.Any) -> None:
     import os
-    print(os.getcwd())
\ No newline at end of file
+    print(os.getcwd())
diff --git a/commands/rename.py b/commands/rename.py
index e69de29..f198c5a 100644
--- a/commands/rename.py
+++ b/commands/rename.py
@@ -0,0 +1,19 @@
+import os
+import typing
+
+command_help: str = 'Rename a file. Usage: rename <old_file> <new_file>'
+
+
+def run(args: typing.Any) -> None:
+    if not args:
+        print('Usage: rename <old_file> <new_file>')
+        return
+
+    if len(args) != 2:
+        print('Usage: rename <old_file> <new_file>')
+        return
+
+    try:
+        os.rename(args[0], args[1])
+    except Exception as e:
+        print(f'Error: {e}')
diff --git a/commands/whoami.py b/commands/whoami.py
index 045050a..8c7a72c 100644
--- a/commands/whoami.py
+++ b/commands/whoami.py
@@ -1,3 +1,8 @@
-def run(args):
-  import getpass
-  print(getpass.getuser())
+import typing
+
+command_help: str = 'Get current user'
+
+
+def run(_args: typing.Any) -> None:
+    import getpass
+    print(getpass.getuser())