int i = 0; //string iterator
char buf[3] = {0};
int partcnt = 0;
int numdots = 0;

//start reading the input
for (;;i++)
{
//read a character from str => str[i]

//test that it is valid
if ((str[i] '9') && str[i] != '.' && str[i] != '')
{
return FALSE;
}

//str[i] is a valid character

//if it is a number 0-9
if( str[i] >= '0' && str[i] = 3)
{
return FALSE;
}

//add it to the buffer
buf[partcnt] = str[i];
partcnt++;

continue;
}

//if we are at a dot or the end
if (str[i] == '.')
{
//check that we have a valid number of chars in buff.
//they are sureley valid numbers because they were verified in the condition above
if (partcnt == 0)
{
//no chars before dot, sorry
return FALSE;
}

//check validity of the buffer contents
int k;
int rank = 1;
int val = 0;

if (buf[0] == '0' && partcnt != 1)
{
return FALSE;
}

//first parse the number
for (k = partcnt-1; k>=0; k--)
{
val += ((buf[k] - '0') * rank);
rank *= 10;
}
//then check the val
if (val 255)
{
return FALSE;
}

//value is good then continue but do not forget to reset the buffer
partcnt = 0;
buf[0]=buf[1]=buf[2] = '';

numdots++;
if (numdots > 3)
{
return FALSE;
}

continue;
}

//final case
if (str[i] == '')
{
if (numdots != 3)
{
return FALSE;
}
if (partcnt == 0)
{
return FALSE;
}

//check validity of the buffer contents
int k;
int rank = 1;
int val = 0;

if (buf[0] == '0' && partcnt != 1)
{
return FALSE;
}

//first parse the number
for (k = partcnt-1; k>=0; k--)
{
val += ((buf[k] - '0') * rank);
rank *= 10;
}
//then check the val
if (val 255)
{
return FALSE;
}

return TRUE;
}

}//endfor