diff --git a/3.1.asm b/3.1.asm
new file mode 100644
index 0000000..771bae5
--- /dev/null
+++ b/3.1.asm
@@ -0,0 +1,93 @@
+.686p
+.model flat
+include kernel32.inc
+includelib kernel32.lib
+includelib msvcrt.lib
+extern _printf:proc
+extern _scanf:proc
+extern _strlen:proc
+_bss segment
+strbuf db 100000 dup(0)
+_bss ends
+.data
+strfmt db "%s",0
+strPrintfFmt db "%s",10,0
+.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, 74
+    cdq
+    mov ebx, 26
+    idiv ebx
+    add edx, 97
+    mov al, dl
+    jmp end_of_proc
+    
+uppercase:
+    sub eax, 42
+    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
+start:
+    push offset strbuf
+    push offset strfmt
+    call _scanf
+    not eax
+    test eax, eax
+    jz exit
+    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 strPrintfFmt
+    call _printf
+    add esp, 8
+    jmp start
+exit:
+    push 0
+    call ExitProcess
+    leave
+    ret
+_main endp
+end _main