Char to Byte - Question

Projects Programming
1

Good Morning,

well I've into array of char value for example:
Character
a[0] = '1' ;
a[1] = '4';

now I would like store 14 value inside byte variable for example b,

Could be fine: convert single value :
Dec Character
49 '1'

b = 49 - byte(a[0]) + 1 ?

How I can covert it ?

Thanks,
Gnux

2

use atoi()

http://www.cplusplus.com/reference/cstdlib/atoi/

byte b = (byte) atoi("14");

Note this will only work on number from 0 to 255

3 
  char a[3] ;
  a[0] = '1' ;
  a[1] = '4' ;
  a[2] = 0 ; // null terminator
  byte b = atoi (a) ;
4

I like to do it by my own. So instead of use atoi() I build my own functions. In this case, with such an easy sting (only 2 chars) you don't even need a 'function'. So, you can do:

  char a[2] ;
  a[0] = '1' ;
  a[1] = '4' ;
  byte b =(a[0]-'0')*10 +  (a[1]-'0');

look that:
'0'-'0' = 0
'1'-'0' = 1
('6' - '0') * 10 = 6*10 = 60
etc.

You can take a look to the ASCII table.

I believe this answer your question, right?

5

Yes Is exatcly what I was thinking ... use :

byte b = atoi (a) ;

i think that is the most correct :slight_smile:

Thanks to all

gnux

6

@luisilva: What happens to the values 0-9 and 100-255? It appears that your algorithm only works for numbers with two digits, unless you require the value 1 to be stored at '0' '1'. Three digits won't work. It wouldn't be hard to create a function that would handle 1 to 3 digits using your approach.

7

Yes, for different number of digits the code must be different. With some loop, for example. But for such small number of digits we don't need to have a big function to do the conversion. And for some one that is starting he can learn what is ASCII, what is a char, a difference between '1' and 1, etc.