312-174

Lab 3

Spring 2000

Due (PreLab, bridge): Friday, 4 Feb 2000, beginning of class.

Due (In-Lab/PostLab): Monday, 7 Feb, beginning of class.

Goals:

1. Understand dynamic memory ( new and delete ).

2. Understand const declarations.

3. Create a robust string ADT.

Requirements.

1. Complete prelab 3 and the bridge exercise from the Data Structures in C++ lab manual by Roberge. You may work in pairs for the PreLab and bridge.

   Turn in your completed pages 45, 49, and 51 in class on Friday. Place all the files that I need to run your solution into a folder labled with your last name(s) and drag it into the appropriate prelab folder in the Turn-In folder on Nova. If I cannot open your folder, double click on your project file, and run your solution (or at least look at it in C++ builder if you haven't completed it), you will not get credit for handing it in.

2. You must next complete lab 3 exercise from the lab book. The Lab must be done individually. This part is due by the beginning of class on Monday, 7 February.

3. Finally, complete postlab exercise 2 . This must be done individually and is due Monday 7 February at the beginning of class.

   Turn in pages 56, 57, and 59 in class monday. Place all of the files that I need to run your in-lab solution into a folder labled with your last name and drag it into the appropriate lab folder in the Turn-In folder on Nova.

Late prelabs, bridges, and postlabs will be penalized as described in the study guide.

All results must be put into the appropriate lab folder on the cs174jb nova account.

All prelabs must have a heading identifying the people who worked on the project. Programs must also contain appropriate comments. See style sheets.

Additional requirements:

1. Note that your subscript operation must check that the subscript is in bounds. If the subscript is out of bounds, return a ! character.

2. The comparison operation (==) must compare two strings character by character.

3. You must use dynamic memory allocation for storing the string. This involves the new and delete operators. (see below).

Hints:

• The new operator is used to create new memory space for a variable. The variable must be a pointer. To create a new integer variable and assign it memory, for example, you would write:

  int *x;

  x = new int;

  To create memory for an array, you must specify how large the array will be:

  int *arr1;

  arr1 = new int[10];

• When you create dynamic memory, it never goes away until you explicitly delete it (at least in C and C++). If you don't delete the variable, the allocated memory remains allocated to your program until the program dies, even if you don't need it any more. This is a common problem in applications and even in Windows 95/98 itself. It's called a memory leak. It is especially egregious in Windows since you never shut the OS itself down. Thus, you find that the longer you run the computer without shutting it down, the less and less memory you have available.

  delete works by simply writing the keyword delete and the name of the variable that you want to delete. Note that the variable name is still valid in the program and you can allocate new memory to it if you wish.

  To delete the memory from an array, you must indicate it is an array by preceding the variable name with brackets, but you cannot specify how much memory to delete. Thus to delete the memory allocated to the array buffer I would say:

  delete [ ] buffer;

  It would be illegal to say delete [20] buffer;

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Last Modified: 4 January 2000

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