Assessment Tool

Lecture 18: Structures

Content Tested: When to use structs versus arrays

Lecture Content:

Data structures
Heterogeneous structures
Type definitions
Field selection
Structs as parameters

Goals:

Develop analytic skills
Develop ability to draw reasonable inferences from observations
Improve memory skills
Develop appropriate study skills, strategies, and habits
Learn terms and facts of this subject
Learn concepts and theories of this subject

Assessment Technique: Categorizing Grids

Purpose:

This activity allows instructors to see if students understand appropriate uses of arrays and structs.

Activity:

This activity will give you the opportunity to decide on appropriate tools for a task. For each of the following scenarios, please indicate if you should use an array or a struct. After deciding on the appropriate data structure, please describe the contents of the data structure as it applies to each situation.

Situation	Array or Struct?	Contents of data structure
1. Keeping track of rainfall data for a year
2. Creating a record for a person in your e-mail address book
3. Sorting high temperatures for the previous month
4. Finding the median score of your last 20 bowling scores
5. Keeping track of the current state of a crossword puzzle
6. Keeping track of a day's weather -- rainfall, high temperature, low temperature, average pressure, percent humidity
7. Storing a customer profile with their account number, current balance, expiration date of charge account
8. Keeping track of 2 players' positions on a 2-dimensional grid

Possible Solutions:

Situation	Array or Struct?	Contents of data structure
1. Keeping track of rainfall data for a year	Array	An array of double values where each value represents a single day's rainfall
2. Creating a record for a person in your e-mail address book	Struct	The struct would contain the person's name (character array) and their e-mail address (character array) and possible a nickname (character array)
3. Sorting high temperatures for the previous month	Array	An array of ints (temperatures usually recording as ints) where each integer is a high temperature from the previous month
4. Finding the median score of your last 20 bowling scores	Array	To find the median, we'll need to sort the scores. The array contains ints where each int represents one of the 20 bowling scores
5. Keeping track of the current state of a crossword puzzle	Array	Probably a 2-D array of characters where ' ' represents a non-filled in square and 'X' (capital X) represents a black square. Other lowercase characters represent the current words.
6. Keeping track of a day's weather -- rainfall, high temperature, low temperature, average pressure, percent humidity	Struct	The struct contains the following fields: rainfall (double), high_temp (int), low_temp (int), pressure (double), and humidity (int).
7. Storing a customer profile with their account number, current balance, expiration date of charge account	Struct	The struct contains the following fields: account_number (int), current_balance (double), month_exp (int), and year_exp (int)
8. Keeping track of 2 players' positions on a 2-dimensional grid	Struct or Parallel Arrays	The struct would keep track of the x and y coordinates of a player. With 2 players, we would have two variables of this new type. OR we could store the x coordinates of both players in an array and the y coordinates of both players in a different array.

Possible Uses of Activity:

Have students work in groups to complete this activity. The instructor may want to circulate throughout the groups to ensure that each group is making progress. After the groups have completed their lists, the instructor can ask for votes on each item. It is important that the instructor explains why each data structure is appropriate for the task.
Have students work individually on their lists and then form groups of 4-5 people to discuss their individual lists with other members of the group.