quote:Original post by White Crow
Hi

I have been reading a book for a couple of days now and there is a source code example which I don''t fully understand:

void main(void)
{
int c, i, nwhite, nother;
int ndigit[10];

nwhite = nother =0;

for(i = 0; i<10;++i)
ndigit = 0;

while ((c = getchar()) !=''q'')
if ( c >=''0'' && c<=''9'')
++ndigit[c-''0'']; //this is my problem
else if (c == '' ''|| c==''\n'' || c == ''\t'')
++nwhite;
else
++nother;

printf("digits =");
for (i=0; i<10; ++i)
printf("%d", ndigit);<br> printf(", white space = %d, other = %d\n", nwhite, nother);<br>}<br><br><br>the problem is that why should I write ++ndigit[c-''0''] instead of ++ndigit[c]? In my eyes it is the same but in the eyes ow the author (and my compiler) it is not. Who can help me? </i> <hr height=1 noshade></SPAN></BLOCKQUOTE><br><br><br>1) You use getchar<br>==>You read a character<br>==>The character is &#111;ne that has ASCII code, its NOT a number(digit), its an ASCII code<br><br>2) You are using the same array namely ndigit to store EITHER white space OR tab OR newlines OR digits OR others.Right? Are LL these numbers?So that''s a hint that you are NOT. <img src="smile.gif" width=15 height=15 align=middle><br><br>3)If you write ndigit[c], you would be storing the number of storing the *number of times you found a digit* at the location ndigit[ascii code of that digit] which is NOT the same as<br>ndigit[c-''0''].<br>For example to store the number of times you found 1, you want to store it at ndigits[1], right?But if you use ndigits[c], then, yuo end up storing the value at <br>ndigit[ascii code of 1] <br>==>ndigit[49] and this is NOT the same as ndigits[1]<br>This is NOT what you wanted, is it?<img src="wink.gif" width=15 height=15 align=middle><br>