Trying to resyrict entry and running total to 32 bit int, but get warning

Total newbie question. I'm trying to restrict a user entry to a 32 bit integer. I keep getting the following warning and when I try to use the restriction it won't work:

[Warning] this decimal constant is unsigned only in ISO C90

This is my code:

Code:

if(testNum == 1 && testLetter == 0)
{
   if(entry[0] == 45)
   {                          
      for(i=1; i<strlen(entry); i++)
      {
       total = total*10+entry[i]-'0';                       
      }
       total = total*-1;
   }
   else
      for(i=0; i<strlen(entry); i++)
      {
       total = total*10+entry[i]-'0';
      }
 if((total > 2147483647) || (total < -2147483648) || (total+runTotal>2147483647) ||  (total+runTotal < -2147483648))
 {
  printf("Number out of range.");
}else
  runTotal += total;
  total = 0;      
  printf("\nNumber:%d\n",runTotal);  
}

Yes I'm sure there are more efficient ways of doing this, but I'm just trying to learn C and get a feel for type sizes and how to work with them.

A 32-bit signed integer can NOT hold a value larger than 2147483647. Thus, checking whether a 32-bit signed integer exceeds this value is illogical. It cannot happen. As I said in another post just a day or two ago, this is like asking, "Is this object outside the universe?" The answer is no.

If you try to do this

Code:

if ( a + b > INT_MAX ) {
  // too late, overflow happened
}

Instead, do this

Code:

if ( a > INT_MAX - b ) {
  // a+b would overflow, so be careful!
}

INT_MAX is in limits.h

Makes perfect sense! Thanks.