diff --git a/ArmNavigation/n_joint_arm_3d/NLinkArm.py b/ArmNavigation/n_joint_arm_3d/NLinkArm.py
index d0e32a05..da562d9f 100644
--- a/ArmNavigation/n_joint_arm_3d/NLinkArm.py
+++ b/ArmNavigation/n_joint_arm_3d/NLinkArm.py
@@ -1,3 +1,7 @@
+"""
+Class of n-link arm in 3D
+Author: Takayuki Murooka (takayuki5168)
+"""
 import numpy as np
 import math
 from mpl_toolkits.mplot3d import Axes3D
diff --git a/ArmNavigation/n_joint_arm_3d/random_forward_kinematics.py b/ArmNavigation/n_joint_arm_3d/random_forward_kinematics.py
index e9479521..87907f80 100644
--- a/ArmNavigation/n_joint_arm_3d/random_forward_kinematics.py
+++ b/ArmNavigation/n_joint_arm_3d/random_forward_kinematics.py
@@ -1,3 +1,7 @@
+"""
+Forward Kinematics for an n-link arm in 3D
+Author: Takayuki Murooka (takayuki5168)
+"""
 import math
 from NLinkArm import NLinkArm
 import random
@@ -17,7 +21,8 @@ if __name__ == "__main__":
                            [0., -math.pi/2, 0., .321],
                            [0., math.pi/2, 0., 0.],
                            [0., 0., 0., 0.]])
-    
+
+    # execute FK 10 times
     for i in range(10):
         n_link_arm.set_joint_angles([random_val(-1, 1) for j in range(len(n_link_arm.link_list))])
         
diff --git a/ArmNavigation/n_joint_arm_3d/random_inverse_kinematics.py b/ArmNavigation/n_joint_arm_3d/random_inverse_kinematics.py
index dd513816..44be2270 100644
--- a/ArmNavigation/n_joint_arm_3d/random_inverse_kinematics.py
+++ b/ArmNavigation/n_joint_arm_3d/random_inverse_kinematics.py
@@ -1,3 +1,7 @@
+"""
+Inverse Kinematics for an n-link arm in 3D
+Author: Takayuki Murooka (takayuki5168)
+"""
 import math
 from NLinkArm import NLinkArm
 import random
@@ -18,6 +22,7 @@ if __name__ == "__main__":
                            [0., math.pi/2, 0., 0.],
                            [0., 0., 0., 0.]])
 
+    # execute IK 10 times
     for i in range(10):
         n_link_arm.inverse_kinematics([random_val(-0.5, 0.5),
                                        random_val(-0.5, 0.5),