Compound data types (CDTs)

Since the Avengers showed up, there’s been a lot more superheros showing up, and frankly - it’s getting quite out of hand.

We want to create a database of superheros to keep track of all of them. To do this, we first want to design a CDT to store all the information about a superhero.

Design this CDT! You should:

  • Decide what the fields should be (and their types).
  • Declare all of these fields in your struct.
  • Create the typedef for this struct and give it an appropriate name.

Keep in mind that there’s many different ways of storing the same information. Some of these have advantages over the other.

Ask your friends how they have chosen to design their data type, and discuss what the advantages/disadvantages of your approaches might be.

Now, in your main() function, declare a couple of variables of this data type, and also a pointer to this data type. After that,

  • Initialize one of the variables directly using the . operator.
  • Initialize another one using the pointer and appropriate operator.
  • Write a function that changes some of the fields of the structs you declared in your main function. (how would you do this?)

Make sure you understand the difference between using a pointer to access a struct and accessing it directly. This will be very important later in the course.

Nested compound data types

Suppose we are designing a database to handle laptop orders for Dell. We’re going to have a top-level CDT that contains information about a laptop a user ordered. Let’s say it stores the following information:

  • Model
  • Memory amount
  • Storage spec
  • Graphics card spec
  • CPU type

Now, here’s the kicker

The Storage spec is itself a CDT that contains:

  • Type of storage (HDD or SSD)
  • Capacity
  • Transfer speed

Also, the Graphics card spec is a CDT that contains

  • Number of processing elements
  • Clock speed
  • Memory capacity
  • Memory bandwidth

Declare the top-level CDT, using appropriate field names and data types. Also, declare at least one of the the storage spec or graphics card spec CDTs.

Now, in your main function, declare and initialize a laptop type variable (your top-level CDT). Answer the following questions:

  • Do we need to separately declare storage spec and graphics card spec?
  • How do we change the values in the storage spec/graphics card spec if we have a variable for the laptop CDT?
  • How do we change the values in the storage spec/graphics card spec if we have a pointer for the laptop CDT?

You’re going to be using CDTs a lot for your upcoming assignments. Make sure you understand how all of this works, so you have an easier time doing those!

Additional Exercises

  1. Create a linked list of superheros using the CDT you created above! Practice implementing the different operations you have learned about.

  2. Vectors are something we often work with in computer science. Write a CDT that represents a (3-dimensional vector), and then implement the functions add(), scale(), dot() to add 2 vectors, multiply a vector by a scalar value, and take the dot product of 2 vectors respectively. What should the input and return types be for each of these functions?

  3. Design and implement a CDT to represent a profile on the new social network “BaceFook”. What information do you think should be stored in it?

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