Lesson How Do You Store All This Data?

Learning Objectives

After this lesson, students should be able to:

• Initialize a two-dimensional array.
• Initialize a new instance of a vector class.
• Store RGB values in a vector.
• Read data from vector and write to a new image.
• Apply new knowledge to the unit's Grand Challenge question.

Tennessee State Standards for C++ Programming Applications (2005)

• Standard 5.0 - The student will write and document an executable program in C++ Programming Language.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

Worksheets and Attachments

Introduction/Motivation

In this lesson, you will learn how a computer image is composed. You will need to understand that a digital image is nothing more than a grid of colors. The grid can easily be stored and manipulated by using nested loops. Following the lesson, students can complete the associated activity Putting It All Together: Programming Robotics Peripheral Vision.

Lesson Background and Concepts for Teachers

Lecture Information

• Two-dimensional arrays are used to store data. Each data point is identified by its horizontal and vertical position in the array. Think of the data as being stored in a grid.
• This address system is similar to the way points on a graph are addressed on an x-y plane, that is, the coordinate points (1, 2) would be one unit from the origin along the x-axis, and 2 units from the origin along the y-axis.

• Similarly, in an array, two subscripts are given, the first standing for the row number, the second representing the column number. By convention, rows and columns are both numbered from 0. Figure 1 shows an example 4 x 3 array and the subscripts representing each point within the array. (Note, the [a][b] notation is unique to C, most other languages refer to the same address as [a,b]).
• The following website explains the use of arrays in computer programming in more detail and gives example coding: https://www.tutorialspoint.com/computer_programming/computer_programming_arrays.htm

Summary

• Two ways to pass a pointer to a two dimensional array: subscript notation and typecasting.
• Subscript notation requires that data type of the second subscript needs to match based on the function.
• Typecasting in the function call uses a pointer with offsets inside the function so that information in arrays of differing dimensions can be processed using the same function.
• A vector template class allows for a dynamic array, which can be expanded to account for input of different amounts of information.

Associated Activities

• Putting It All Together: Programming Robotics Peripheral Vision - In the concluding activity of the unit, students write the code to solve the Grand Challenge. The solution takes two images captured by robots and combines them to create an image that can be focused at different distances, mirroring human vision.

Vocabulary/Definitions

array: A block of related data elements, each of which is identified by one or more subscripts.

subscript: Coordinate giving location in a single dimension in an array. Two subscripts together create an address of an element in a two-dimensional array.

Assessment

As homework, have students complete the Data Storage Assignment Handout, which asks them to read data from a 16 x 16 image grid and store the data in an array. Then they are challenged to see if they can flip the image around by using nested loops. Assess their learning by their completion of the 16 x16 grid manipulation code and answers to the handout questions. Then proceed to conduct the associated activity, Putting It All Together: Programming Robotics Peripheral Vision.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under National Science Foundation RET grant nos. 0338092 and 0742871. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.