Thread: sequential file program

This program is quite elegant in it's use of pointers. Except for the memory leak, it's a gem, and clearly, not your original code. However, after the original wheel, there has never been an original outside rim shape for any wheel, either. They're all round.

NHBad, take a look at the transaction code, and write out in just plain English, what would be the programs logic for each code. Something like:

Code is 0:
a) add a new blank record to the database with an ID number and name.
b) whatever

Code is 1:
a) etc.

etc.

Then we'll take that and form it up into code, using that logic. So if your logic is haywire, the resulting transaction function code, will also be haywire.

Time is of the essence here. If you take a week or ten days to get back with your input, you're taking a big chance nobody will still be interested in this program. In about a week, I will be starting another programming project, and be quite unavailable. If you want to finish this project with assistance from this forum, I'd put it in high gear. As you've seen, a simple bump is not much help.

Originally Posted by needhelpbad

okay, so the types are:

Code:

4. The keys should be in sorted order, with duplicates.  The interpretation is as follows:
Type = 0, insert a new record with name name and key key, and all other values 0.  
key should have at least one character, that is, strlen (key) > 0.

Type = 1, 2, or 3, add value points to test.  (value may be negative.)  
Check for constraint on resulting test score.	

Type = 4, add one assignment and value points for homework, checking the constraint. 
 value should be non-negative, and less than or equal 5.

Type = 5, add value points for homework, without changing hwCount.  
Total hwPoints should not exceed 5 * hwCount.

Thus, how I see it goes is:

So fleshing this out to code, partway:

Code:

switch (trans)   {
   case 0: inserts a new record with a name and key in their respective spots with rest of
                the values zero; 
                break;  

   case 1: insert value for test1; break;
   case 2: insert value for test2; break;
   case 3: insert value for test3; break;

   case 4: add a value to hwCount; 
                add additional value points for homework, maxing at 5;
                break;

   case 5: add value points to the homework parameter (hwPoints) without changing
                hwCount with the total not exceeding 5*hwCount
                break;

}

I'll add some more to it, later. Looks like a start, though.

obviously im new to this, but ive never seen "switch"

how does it act, compared to such as a struct or a void?

Originally Posted by needhelpbad

obviously im new to this, but ive never seen "switch"

how does it act, compared to such as a struct or a void?

I don't even know what that question means. A struct is an object (a group of variables, held together by a common name), and doesn't act at all. Void is just a keyword used to denote that a function either doesn't return a result or doesn't take any parameters (depending on where it's used), or as a sort of generic type (a "void pointer" is a pointer to ... something that we don't know what it is).

A switch is program control, like if, or while, or for. Get your textbook (or favorite C tutorial site), and look up "switch" in the index.

A switch statement is just like a series of if statements, and is very useful and elegant to use, where you have a large number of choices to be made by your program.

You could code it like this:

Code:

if(trans == 0)   {
    //list the various things to do if trans is 0
}
else if(trans == 1)   {
   //list the various things for the program to do if trans is 1
}
else if(trans == 2)   {
   //etc.

etc.

okay, that makes a lot more sense, ill see what i can do with it

I'd start with something simpler, at first. The switch statement for the sequential file program will still need more code, in order to function.

Code:

int number;

printf("\n Enter a number between 1 and 3");
scanf("%d, &number);

switch (number)   {

   case 1: printf("\n You entered a one"); break;
   case 2: printf("\n You entered a two"); break;
   case 3: printf("\n You entered a three"); break;

//but watch this:
   case 0: printf("\n That's not between 1 and 3");  //no break
   case 4: printf("\n Please read more carefully, next time");  //no break

   default: printf("\n Because I won't always be here to remind you"); break;
}

Switch statements have a unique "fall through" feature, unlike anything else in the C syntax, that I know of. It can be very useful, but it will catch you badly if you forget the break statement you usually need, at the end of each case statement.

looking how this transaction data is coming, does my actual seq_trans file look like it would apply?

Code:

3	100	5	Jeff	
4	101	5	Mark	
1	102	3	Jenn	
2	103	5	Chris	
4	104	4	Matt	
3	105	3	Dan	
0	106	4	Dave	
5	107	14	Rich	
3	108	2	Mike
1	109	4       Tony	
4	110	5	Rob	
2	111	-4	Sonny	
3	112	4	Luke	
4	113	3	April	
2	114	9	Sheryl	
4	115	4	Tom	
5	116	18	Lamont	
1	117	3	Steve	
2	118	1	Jake	
3	119	3	Austin	
0	0	0

and is this how the coding would go for the switches? be gentle.

Code:

switch(trans) {

if(trans == 0)   {

printf("Enter a key and name, respectively.");
scanf("%d%d", &theId, &theName);

theTest1 = 0;
theTest2 = 0;
theTest3 = 0;
theHwCount = 0;
theHwPoints = 0;

   }
else if(trans == 1)   {

printf("Enter value for test 1");
scanf("%d", &theTest1);

   }
else if(trans == 2)   {

printf("Enter value for test 2");
scanf("%d", &theTest2);

   }
else if(trans == 3)   {

printf("Enter a value for test 3");
scanf("%d", &theTest3);

   }
else if(trans == 4)   {

printf("Enter a value for homework count");
scanf("%d", &theHwCount);
printf("Any additional points for homework? (0 -> 5)");
scanf("%d", &theHwPoints);

   }
else if(trans == 5)   {

printf("Enter a value for extra homework points, not exceeding 5 times actual homework count");
scanf("%d", &theHwPoints);

   }
}

Originally Posted by needhelpbad

looking how this transaction data is coming, does my actual seq_trans file look like it would apply?

Code:

3	100	5	Jeff	
4	101	5	Mark	
1	102	3	Jenn	
2	103	5	Chris	
4	104	4	Matt	
3	105	3	Dan	
0	106	4	Dave	
5	107	14	Rich	
3	108	2	Mike
1	109	4       Tony	
4	110	5	Rob	
2	111	-4	Sonny	
3	112	4	Luke	
4	113	3	April	
2	114	9	Sheryl	
4	115	4	Tom	
5	116	18	Lamont	
1	117	3	Steve	
2	118	1	Jake	
3	119	3	Austin	
0	0	0

I don't believe so. It should have repeats of ID and name with their test score additions, etc.

and is this how the coding would go for the switches? be gentle.

Code:

switch(trans) {

case 0: //no if(trans == 0)   { needed.

printf("Enter a key and name, respectively.");
scanf("%d%d", &theId, &theName);

theTest1 = 0;
theTest2 = 0;
theTest3 = 0;
theHwCount = 0;
theHwPoints = 0;

   }
case 1: //no else if(trans == 1)   { needed.

printf("Enter value for test 1");
scanf("%d", &theTest1);

   }

case 2: //no else if(trans == 2)   { needed

printf("Enter value for test 2");
scanf("%d", &theTest2);

   }
//etc.
else if(trans == 3)   {

printf("Enter a value for test 3");
scanf("%d", &theTest3);

   }
else if(trans == 4)   {

printf("Enter a value for homework count");
scanf("%d", &theHwCount);
printf("Any additional points for homework? (0 -> 5)");
scanf("%d", &theHwPoints);

   }
else if(trans == 5)   {

printf("Enter a value for extra homework points, not exceeding 5 times actual homework count");
scanf("%d", &theHwPoints);

   }
}

Nope, sorry. The "job" of a switch statement is to remove a lot of if statements. Here, you start with a switch statement, and then proceed with the if statements, anyway.

Play and experiment with the simple switch statement I gave you earlier, and you'll get the hang of it.

That's a good start to using a switch statement. An important error control feature is this:

Code:

scanf("%d", &number);

switch (number)   {

   case 0: //code for zero; break;
   case 1: //code for one; break;
   etc.

   default: printf("\n      Error #1 has Occurred in the Program!");
                //your program should never reach this line, but has
}

You would be surprised how often a simple error-catcher like default in a switch statement, can catch a bug in your code. I don't always use it for a simple program, but I recommend it, and use it for non-trivial programs.

It's a 10.

For the sequential file program, the logic you show is not complete, but it's a start.

adding in the default;

Code:

int trans;

printf("\n Which transaction type is needed? (0-5)");
scanf("%d", &trans);

switch(trans) {

case 0: 
printf("Enter a key and name, respectively.");
scanf("%d%d", &theId, &theName);

theTest1 = 0;
theTest2 = 0;
theTest3 = 0;
theHwCount = 0;
theHwPoints = 0;
break;

case 1: 
printf("Enter value for test 1");
scanf("%d", &theTest1);
break;

case 2: 
printf("Enter value for test 2");
scanf("%d", &theTest2);
break;

case 3:
printf("Enter a value for test 3");
scanf("%d", &theTest3);
break;

case4:
printf("Enter a value for homework count");
scanf("%d", &theHwCount);
printf("Any additional points for homework? (0 -> 5)");
scanf("%d", &theHwPoints);
break;

case 5:
printf("Enter a value for extra homework points, not exceeding 5 times actual homework count");
scanf("%d", &theHwPoints);
break;

default: printf("You have encountered an error!");

}

I'm not noticing where my logic is imcomplete, I am sure I have a bunch wrong or that could be fixed, I am just not recognizing it

Don't these values have to be written to the file?

I think so.

seems like the easiest things are the easiest to miss..

so I know I would have to intertwine writeRecord function in there, but..im not sure how it would work

for something like case 3, would it be..

Code:

case 3:
printf("Enter a value for test 3");
scanf("%d", &theTest3);
writeRecord(&theTest3);

//or maybe

writeRecord(theStudentPtr->test3);
break;

or something along those lines?