UTPA STEM/CBI Courses/Computer Science/Selection

Course Title: Computer Science I

Lecture Topic: Selection

Instructor: Laura Grabowski

Institution: UTPA

Backwards Design

Course Objectives

• Primary Objectives- By the next class period students will be able to:
  • Understand concepts of how selection structures work: Test current condition (while program executes), outcome of test, decision based on outcome
  • Understand how different selection structures work (if, if/else, nested if/else, switch)
  • Write C++ code for different selection structures

• Sub Objectives- The objectives will require that students be able to:
  • Write logical and relational expressions
  • Identify syntax errors in selection statements

• Difficulties- Students may have difficulty:
  • Understanding the underlying concepts involved
  • Remembering the correct syntax for the conditional expressions

• Real-World Contexts- The concepts of decision-making are grounded in the real world -- we do it all the time. The details of this lesson, however, relate specifically to the context of learning how to design and write computer programs. In that context, some interesting applications include:
  • Designing video games
  • Comparison-based searching and sorting algorithms

Model of Knowledge

• Concept Map
  • Analysis of problem, requires
    • Critical thinking skills
    • Summarizing skills
  • Design of solution (algorithm design), requires
    • Problem decomposition skills
    • Understanding of underlying programming concepts
      • Data types
      • Sequence
      • Control structures
        • Selection -- this lesson
        • Repetition
      • Modular programming (functions)
      • Arrays
      • Abstract data types
        • Structures
        • Classes
      • Pointers
      • Data structures and algorithms
        • Trees
        • Searching
        • Sorting
    • Use of design tools -- pseudo-code writing skills
  • Implementation of solution
    • Tools of the trade
      • Learned in Lectures through
        • Slides
        • Analogies
        • Sample programs
        • Group exercises
      • Using C++ to implement underlying concepts (listed above)
      • Applying underlying concepts, covered in lectures using
        • In-class exercises
        • Lab assignments
        • Homework assignments

• Content Priorities
  • Enduring Understanding
    • Understand fundamental programming concepts
    • Understand basics of algorithm design
    • Be able to design, write, debug, and test simple programs in C++
  • Important to Know and Do
    • Familiarity with programming environments such as Microsoft Visual C++
    • Document algorithm design with tools such as pseudo-code and flow diagrams
  • Worth Being Familiar with
    • Time management

Assessment of Learning

• Formative Assessment
  • In Class (groups)
    • Pre-lesson quiz after student has read chapter.
    • Team coding exercises: Work with the group to write code for selection statements.
    • Code traces. Walk though code fragments provided and determine how statements will execute based on differing conditions at run-time.
  • Homework (individual)
    • Lab assignments using selection
    • Worksheet: writing selection code fragments, executing code traces
• Summative Assessment
  • Unit quiz
  • Exam

Legacy Cycle

OBJECTIVE

By the next class period students will be able to:

• Understand concepts of selection structures: Test current condition (while program executes), outcome of test, decision based on outcome
• Understand how different selection structures work (if, if/else, nested if/else, switch)
• Write C++ code for different selection structures

The objectives will require that students be able to:

• Write logical and relational expressions
• Identify syntax errors in selection statements

THE CHALLENGE

You want to enter a game programming contest. You need to write a program to play the game “Rock-Paper-Scissors”. To win the contest, your game must be able to beat a human player in at least five out of ten consecutive games. How can you make your program win the contest?

GENERATE IDEAS

• Play several rounds of two-player “Rock-Paper-Scissors” with your group.
  • Make sure everyone understands how the game works.
  • Observe, record your ideas about, and then discuss:
    • What strategies did you try?
    • What strategies seem to win?
• Think about and write down your ideas about how you might write an algorithm to implement the game (individually).
• Discuss your algorithm ideas with your group.
• Brainstorm on what you need to implement your algorithms in C++
  • What do you know that you can use?
  • What do you sort of remember but need to review or have more details on?
  • What don’t you know that you need to know in order to solve the problem?

MULTIPLE PERSPECTIVES

• From the group discussions, groups share with class
  • What sorts of strategies do you need to implement to program the game?
  • What do you know? What do you need to know to solve the problem?
• Lecture on selection (if, if/else, nested if/else) to help students gain understanding of selection structures. Organizing question for the lecture is “What do we need to know in order to write our “Rock-Paper-Scissors” program?
  • The rules of the game
  • How to compare the players’ actions (relational and logical tests) and make decisions based on what is happening at program run-time (selection).

RESEARCH & REVISE

• Students will work in groups to complete an exercise on writing code for simple selection statements.
• Students will outline their ideas for the “Rock-Paper-Scissors” program.

TEST YOUR METTLE

Students will receive feedback on their exercise solutions and on their game program ideas. Students will be given a quiz at the beginning of the next class.

GO PUBLIC

Students will be able to answer the questions about how to make run-time decisions in a program. Students will also complete lab assignments and homework assignments that focus on using selection structures.

Pre-Lesson Quiz

For Questions 1-4, use the following declarations to evaluate the given expressions as TRUE or FALSE.

int x = 8;
int y = 15;
double myVal1 = 2.5;
double myVal2 = 5.8;

1 x < y

	TRUE
	FALSE

2 x != x

	TRUE
	FALSE

3 myVal1 > myVal2

	TRUE
	FALSE

4 myVal2 < 5.9

	TRUE
	FALSE

5

Given the declarations

bool legalAge;
int age = 23;

is legalAge true or false after the following statement is executed?

legalAge = (age >= 21);

	TRUE
	FALSE

Test Your Mettle Quiz

1 Which of the following C++ statements is an example of one-way selection?

	if (score < 60) grade = ‘F’ else grade = ‘P’;
	if (score < 60) grade = ‘F’;
	if (score < 60) grade = 'F' else if (score > 89) grade = 'A';

2

The expression

if hours < 40

contains a syntax error. Which of the following corrects that error?

	if hours < 40;
	if int hours < 40
	if (hours < 40)

3

The expression

if (balance = 0)

contains a logical error. Which of the following corrects that error?

	if (balance == 0)
	if (balance = 0);
	if (balance != 0)

4 What will be the output of the following code if the input is 5?

int value;
bool correct = false;
cin >> value;
if (value == 8)
   correct = true;
if (correct)
   cout << "Great job!"
else
   cout << "Nope, fooled you!"

	Great job!
	Nope, fooled you!
	Nothing is output