Please diagnose my pointer problem

dear all,

i'm writing program project revolves around need dynamically allocate big chunk of memory. whatever reason, , despite searching, reading relevant chapters in books have, still unable easy setting value of char in memory allocated. example:

code:

int main(int argc, const char * argv[])  {        unsigned char* ptr;            ptr = calloc(1000, sizeof(char));            *ptr  = 0;      *(ptr+1) = 1;      *(ptr + 2) = 2;      *(ptr + 3) = 3;            printf("%c" , *(ptr + 2) );            return 0;  }    

this prints upside down question mark - not expected!

ideas on stupid thing i'm doing?

many thanks,

david

 

use %d instead of %c. %c prints variable character mapping ascii, ascii values in region not printable characters:

code:

       decimal set:           0 nul    1 soh    2 stx    3 etx    4 eot    5 enq    6 ack    7 bel         8 bs     9 ht    10 nl    11 vt    12 np    13 cr    14    15 si  

edit:

if intend use characters, need enclose values in single quotes:

code:

      *ptr  = '0';      *(ptr+1) = '1';      *(ptr + 2) = '2';      *(ptr + 3) = '3';            printf("%c" , *(ptr + 2) );  

 

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