如何检查是否一些重presents在NASM大会大写字符？ [英] How to check if a number represents an uppercase character in NASM Assembly?

问题描述

假设你有存储在 EAX 的数字。如何检查这个数字再$ P $是否psents大写字符或不？

Suppose that you have a number stored in EAX. How can I check whether this number represents an uppercase character or not?

坦率地说，我没有尝试过任何东西。我最近的想法是创造的大写字符（'A'，'B'，'C'D'，...）的数组，然后检查是否 EAX 等于任何这些。有没有更简单的方式在NASM大会做到这一点？

Frankly, I haven't tried anything. The closest idea I had was to create an array of upper case characters ('A','B','C,'D',...) and then check if EAX was equal to any of these. Is there a simpler way to do this in NASM Assembly?

我使用的是64位的CentOS，对于32位程序。

I'm using 64-bit CentOS, for a 32-bit program.

推荐答案

有关ASCII字符，像这样的工作：

For ASCII characters, something like this would work:

cmp eax,'A'
setnc bl    ; bl = (eax >= 'A') ? 1 : 0
cmp eax,'Z'+1
setc bh     ; bh = (eax <= 'Z') ? 1 : 0
and bl,bh   ; bl = (eax >= 'A' && eax <= 'Z')
; bl now contains 1 if eax contains an uppercase letter, and 0 otherwise

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