A gist for a toUpper function written in C

C - toUpper function

p1 = cadena1;
p2 = cadena2;

for (int i = 0; i < strlen(cadena1); i++)
{
  if (*p1 > 'a' && *p1 < 'z')
    *p2 = *p1 + ('A' - 'a');
  else *p2 = *p1;
  p1++;
  p2++;
}