strtoul                                                                           #include <stdlib.h> 

unsigned long int strtoul (const char* str, char** endptr, int base);

Parameters

str

C-string containing the representation of an integral number.

endptr

Reference to an object of type char*, whose value is set by the function to the next character in str after the numerical value.
This parameter can also be a null pointer, in which case it is not used.

base

Numerical base (radix) that determines the valid characters and their interpretation.
If this is 0, the base used is determined by the format in the sequence (see strtol for details).

Return Value

Example

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/* strtoul example */
#include <stdio.h>      /* printf, NULL */
#include <stdlib.h>     /* strtoul */

int main ()
{
  char buffer [256];
  unsigned long ul;
  printf ("Enter an unsigned number: ");
  fgets (buffer, 256, stdin);
  ul = strtoul (buffer, NULL, 0);
  printf ("Value entered: %lu. Its double: %lu\n",ul,ul*2);
  return 0;
}

Enter an unsigned number: 0x7ff
Value entered: 2047. Its double: 4094