title: Is there any way to detect invalid characters when using ReadHex function in assembly(masm32)?
body: <p>I wanted to create a program that receives new value if the input value(32-bit hexadecimal) is not correct. Using a ReadHex function was very useful for this, but I have no idea about how to detect invalid characters. </p>
  
  <p>I tried entering invalid characters on purpose to see what that does on <code>EAX</code> register, but it just considers invalid characters as 0. </p>
  
  <p>ex) <code>4FZC</code> becomes <code>4F0C</code></p>