Adding records to a 2 dimensional database.

Hi Guys,

Im working on an exersiz that requires the user input a name , 4 scores and an ID number for the record being added.

I had it all going but when I try to add the ID numbers taken from the user and do a check to see if the number is taken ive got a little lost.....

I wonder if anyone can point out the flaws in my function below?

Regards as ever
Colin

Code:

void add_new_name(void)

{

int found=0;
int record_id;
int loop=0;
clrscr();

/* Add the name and DOB & ID to the database*/

printf("\n\n\t\t   Enter new name and Grades\n\n");
printf("Enter new name: ");
gets(names_database[index].name);
flush(stdin);

printf("Please enter 4 grade marks in as a percentage value:\n\n");
scanf("%d%d%d%d",&names_database[index].grade1, &names_database[index].grade2,&names_database[index].grade3,&names_database[index].grade4);
fflush(stdin);

printf("Please enter an ID number between 100-999\n");
scanf("%d",&record_id);
fflush(stdin);


while(found=0 && loop < MAX)
{

 if(record_id == names_database[loop].id)

{
printf("This ID number is taken");
printf("Please Re-enter an ID number between 100-999\n");
scanf("%d",&record_id);
fflush(stdin);
}

loop++;

}

if(found=0)
{
names_database[loop].id = record_id;
}

/* Increment the student array */
index++;

}

>> gets(names_database[index].name);
>> flush(stdin);

1) don't use gets() - use fgets() to prevent buffer overflow.
2) fflush() is not intended for input streams - read the FAQ for more reliable ways to do that.
3) what happens when you enter the function and index > MAX?


>> while(found=0 && loop < MAX)

I don't see where 'found' is actually used, but at any rate, you're setting it - not testing it - with the value of zero each iteration. and there's no sense in testing data from 'index' through 'MAX' since there isn't any valid data there anyway.

>> if(found=0)

again, this should be ==.

>> if(record_id == names_database[loop].id)

what happens if the new 'record_id' corresponds to a value already passed in previous iterations of the loop? for instance, let's say the first 4 id's are:

98
21
72
35

suppose the user chooses '72'. when you find that value at position three you prompt for a new number and the user chooses '98' - since you didn't restart loop you'll never know that number is already taken, too.

>> names_database[loop].id = record_id;

'loop' is going to be MAX - 1, what you want is the element at 'index'.

Hi Sebastiani

Thanks for your reply,

Im still a little stuck, forgive me Im a newbie to C.....

Im sure its my loop thats wrong but I cant puzzle it out as yet.

Here is what I tried after your suggestion, I cant think how to recheck the ID once its has been entered again??

Perhaps you couls assist me again.

Thanks again

Code:

while(found==0 && loop < MAX)  /*Max is defined as 999*/
{

if(record_id == names_database[loop].id)

{
found=1;
printf("This ID number is taken");
printf("Please Re-enter an ID number between 100-999\n");
scanf("%d",&record_id);
fflush(stdin);
}

loop++;

}

if(found==0)
{
names_database[loop].id = record_id;
}

/* Increment the student array */
index++;

something like:

Code:

 int retry = 1; 
 while(retry) 
 {
  retry = 0; 
  loop = 0;
  while(loop < index)  
  {
   if(record_id == names_database[loop].id)
   {
    printf("This ID number is taken");
    printf("Please Re-enter an ID number between 100-999\n");
    scanf("%d",&record_id);
    fflush(stdin);
    retry = 1;
    break; 
   }
  loop++;
  }
 }

>> names_database[loop].id = record_id;

again, you're not assigning the id to the proper array element.

Hi there,
Thanks for your quick reply,

Can you tell me what "while(retry)" means??

Thanks again

It is a variable that is set to 1 when the user has to enter the data.

That way the user will keep getting that message and have to enter the data until they enter valid input.

conditionals always evaluate the non-zero-ness of a condition. so:

while(retry)

is semantically the same as:

while(retry != 0)

Thanks Guys,

I will see how I get on....Your comments are very appreciated.

Regards as ever.