所以，我有一段代码设置边界来检查字符是否是字母（不是数字，不是符号），但我认为它不适用于大写和小写之间的字符。你能帮我吗？谢谢！
mov al, byte ptr[esi + ecx]; move the first character to al
cmp al, 0 ; compare al with null which is the end of string
je done ; if yes, jump to done
cmp al, 0x41 ; compare al with "A" (upper bounder)
jl next_char ; jump to next character if less
cmp al, 0x7A ; compare al with "z" (lower bounder)
jg next_char ; jump to next character if greater
//do something if it's a letter
next_char: …