CIS3355: Business Data Structures
Fall, 2008
 

Numeric/Character Arrays Part 2

Let's write the code necessary to carry out the menu options listed in part 1:

Choice 1: Display the list of people.

This is pretty simple. We know how many people there are (we stored this value in variable/location numberpeople). Now all we have to do is print out the list using a for loop. I added the variable offset (as a short integer) into my list of variable declarations for this purpose. So the basic command is simply:

for (offset = ??; offset < ??; ??)

I think you can figure out what is missing. Here is how my output appears:

You'll notice that after I finished listing the people, I prompted the user to return to the main menu, and we did.

You will also notice that my output is formatted. Since we didn't spend much time in formatting, I will give you the print string:

printf("%-20s %3d %5.3f\n,personname[offset], personage[offset], persongpa[i])

There are easily fixed errors in the code above.

Choice 2: Add a new person to the list

Again, this is pretty simple. We already know that there numberpeople on the list. All we have to do  stored at get the user's input and store them at index/offset [numberpeople]. Then we have to increment the value of numberpeople.

That might initially sound strange (storing the values at offset numberpeople and THEN incrementing the value. But think about it. Right now, the value of numberpeople is 5 (five), but they on stored on offsets [0] ... [4]. We want to store our new values at offset [5] (the present value stored at location numberpeople), and then increment the value stored at numberpeople to 6 (the number of people NOW on our list).

Here is how my program did it:

Notice that my program printed out the new list before returning to the main menu. HOW??  I simply copied and pasted the code I used in my listing routine (above). We will clean this up later.

There are a few things you have to be aware of. Cin and cout have some anomolies associated with them. Using the commands:

cout << "Enter the new person's age: ";
cin >> personage[numberpeople];

Should give you no problems. However, if you use the command:

cout << "Enter the new person's age: ";
cin >> personage[numberpeople];

You might run into problems (especially if you enter spaces and other delimiters. So, I will give you some straight-forward C commands to get the user input and store it (all you need to do is put this snippet of code in your program):

printf("Enter the new person's Name: ");
gets(temp);
strcpy(personname[numberpeople], temp);

The only command that needs a little explanation is strcpy. strcpy is a function which copies a string to another string. It takes two arguments: (The string you want to copy to, The string you want to copy from). Actually, it takes:

(The address you want to copy the string to, The address of the string you want to copy from)

The function is located in the file string.h, so make sure you include the file at the top of your file.

Choice 3: Change a person's name

This is also pretty easy, but there is something you should do beforehand. You will notice that choices 3, 4, and 5 require you to first identify the person whose record the user wants to change. That means you need to get the offset of the array number, and then replace whatever is in that location with the user input.

Let's take a look at my output first:

Notice that after menu option 3 was chosen, I once again displayed the list (A copy and paste job), but this time with the index/offset number before the person's information. I then checked to make sure that the user entered a valid number (this uses the same basic logic that we used to check for a valid menu choice), and stored it at location personnumber. I didn't let the user get away with making an invalid choice. If they entered a valid choice, this is what the output would look like:

All I did was print out the name, and get the information. Once again, be careful with cin. Again, I used the code:

printf("Enter a new name for %s: , personname[??]);
gets(temp);
strcpy(personname[??], temp);

I think you can figure out the missing information (and catch the other simple error).

Once again, I printed out the entire list of people. How?? the same way I did it the other two times.

Choice 4: Change a person's age

This is simply a take-off on changing a person's name (actually much simpler). Once again, I found out the address where the information is stored (by getting the array offset), prompting the user, getting the user input, and printing the information. Here is my output:

I used the command:    cin >> personage[personnumber]; to get the user input.

Choice 4: Change a person's GPA

This is almost identical to choice 3, except that we are getting a real number instead of an integer. Once again, I found out the address where the information is stored (by getting the array offset), prompting the user, getting the user input, and printing the information. Here is my output:

Once again, I used the cin command.

Get this up and running, and we will go onto the final part of the assignment.