Re: subtract two char value?

[Scott Klement <c400-l@xxxxxxxxxxxxxxxx>]

In C, a 'char' field is the same as RPG's 3I 0 (or 3U 0 if you're using 
unsigned characters).  It's an 8-bit binary integer.  When you put a 
character in single quotes, it looks up the EBCDIC value of that 
character, and puts that number into the variable.

'char' variables in C are numeric variables.

so if you had the following C code:

      char c;
      c = '1';

On an EBCDIC system, that would've put the value 241 into the variable 
named 'c'.  (or x'F1'... if you look at an EBCDIC chart, you'll see that 
the number 1 is x'F1' in EBCDIC).

The Hex2Int() routine that you're using is intended to convert a hex 
character, from 0-9, or A-F into a number.  So characters from 0-9 
should come back with a numeric value of 0-9, and characters from A-F 
should come back with a number from 10-15.  I think you can see how the 
10-15 part works.

So if you take '1' - '0', what do you get?   x'F1', or 241 minus x'F0' 
or 240.  241-240=1... the number one.   likewise, 9 is 249, and 249-249=9.




Lim Hock-Chai wrote:
> I ran into code below and confuse about the line where it subtract two
> char fields:
>  
> unsigned int Hex2Int(char cC)       
> {                                   
>    switch(cC)                       
>    {                                
>       case 'a':return(10);break;    
>       case 'b':return(11);break;    
>       case 'c':return(12);break;    
>       case 'd':return(13);break;    
>       case 'e':return(14);break;    
>       case 'f':return(15);break;    
>       case 'A':return(10);break;    
>       case 'B':return(11);break;    
>       case 'C':return(12);break;    
>       case 'D':return(13);break;    
>       case 'E':return(14);break;    
>       case 'F':return(15);break;    
>       default:return(cC-'0');break;   <== What is this mean?  How can C
> subtract two char values?
>    }                                
>    return(0);                       
> }                                   
>
>
> I wrote a test program below and the result of 'H'-'0' is 'Q'.  Huh?
>  
> int main(void)   
> {                
>  char cC;        
>  char result;    
>  cC = 'H';       
>  result = cC-'0';
> }