Assembly Code: Can someone help me understand what this C program is doing in each step? I supposed to be a rotational cipher.

Sub 401000 proc near Push eb Mov ebp, es Movzx eax, [ebp + arg 0] , 61h Jl short loc 401034 Movzx ecx, [ebp+arg0 7Ah Ug short lo 401034 , Movzx edx, [ebptarg 0 Add edx, Odh Movzx eax, [ebp+arg 0] cmp eax. 7Ah Jle short loc 401032 Movzx ecx, [ebp+arg0 Sub ecx, 1Ah Mov [ebptarg0 oc 401063 Mov al, ebptargo 01 Pop eb Reth Sub 401000 end Movzx eax, [ebp+arg 0] Sub eax, 1 Movzx ecx, [ebp+arg0 Add ecx, 0Dh oy lebp+arg 0], cl Sub 401000 proc near Push eb Mov ebp, es Movzx eax, [ebp + arg 0] , 61h Jl short loc 401034 Movzx ecx, [ebp+arg0 7Ah Ug short lo 401034 , Movzx edx, [ebptarg 0 Add edx, Odh Movzx eax, [ebp+arg 0] cmp eax. 7Ah Jle short loc 401032 Movzx ecx, [ebp+arg0 Sub ecx, 1Ah Mov [ebptarg0 oc 401063 Mov al, ebptargo 01 Pop eb Reth Sub 401000 end Movzx eax, [ebp+arg 0] Sub eax, 1 Movzx ecx, [ebp+arg0 Add ecx, 0Dh oy lebp+arg 0], cl