.686p
.model flat
include kernel32.inc
includelib kernel32.lib
includelib msvcrt.lib
extern _printf:proc
extern _scanf:proc
extern _strlen:proc
.data
strbuf db 1000 dup(0)
strfmt db "%s",0
.code
process_char proc
    mov eax, [esp+4]
    cmp eax, 65
    jl check_if_lower
    cmp eax, 90
    jg check_if_lower
    jmp uppercase
check_if_lower:
    cmp eax, 97
    jl end_of_proc
    cmp eax, 122
    jg end_of_proc
    
lowercase:
    sub eax, 84
    cdq
    mov ebx, 26
    idiv ebx
    add edx, 97
    mov al, dl
    jmp end_of_proc
    
uppercase:
    sub eax, 52
    cdq
    mov ebx, 26
    idiv ebx
    add edx, 65
    mov al, dl
    
end_of_proc:
    ret

process_char endp
_main proc
    push ebp
    mov ebp, esp

    push offset strbuf
    push offset strfmt
    call _scanf
    add esp, 8
    
    push offset strbuf
    call _strlen
    add esp, 4
    
    mov ecx, eax
    test ecx, ecx
    jz for@end
for@start:
    dec ecx
    
    movzx eax, byte ptr strbuf[ecx]
    push eax
    call process_char
    add esp, 4
    
    mov byte ptr strbuf[ecx], al
    
    test ecx, ecx
    jnz for@start
for@end:
    push offset strbuf
    push offset strfmt
    call _printf
    add esp, 8
    push 0
    call ExitProcess
    leave
    ret
_main endp
end _main