Week 6 Solution

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Description

Overview

This hands-on lab allows you to follow and experiment with the critical steps of developing a program including the program description, analysis, test plan, design and implementation with C code. The example provided uses sequential, repetition statements and nested repetition statements.

Program Description

This program will calculate the average of 3 exams for 5 students. The program will ask the user to enter 5 student names. For each of the students, the program will ask for 3 exam scores. The average exam score for each student will be calculated and printed.

Interaction

Starting with this project, the interactions between the program and the user are getting complicated enough to justify a new section before the Analysis section – a section which will eventually become the User’s Guide. This section is a rather detailed presentation of how the program and the user will interact. A little reflection should make it apparent that neither the Analysis nor the Test Plan can really proceed without an understanding of how the program will work from the user’s perspective.

At the moment, the exact interaction is not defined by the Program Description, so this is our chance to make that interaction clear and convenient, and we will make choices. In this case, we choose to enter the 3 numbers, followed by a name. There should be spaces between the numbers and the between the third number and the student’s name. For this program, we will allow all the information to be on a single line. Here is an example, the prompt in black, the user input in red:

Enter 3 grades and the student’s name: 88.76 93 98.22 Mary

Analysis

New concept: reading, storing and printing a string input from the user.

This is going to require research or an example.

Required storage:

float data: new grade, sum of grades, average of those grades

string data: student’s name

Math:

sum = sum + new grade average = sum / 3

Example of one student:

input: 70 80 90 Jane sum = 0

sum = sum + 70 sum = sum + 80 sum = sum + 90

sum is 240 at this point average = 240 / 3 = 80

Output for one student

Average for Jane is 80 Looping:

for 5 students

    1. reset sum o for 3 grades

      • get grades

o get name

o compute average

o print result for one student end for 5 students

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Test Plan

To verify this program is working properly the input values shown in the table below could be used for testing.

Comments:

Can we make sure that the output is exactly two digits right of the decimal point? Yes! Can we average ANY 3 numbers? Yes!

How should this code behave if there are any deviations from the specified input format?

Any good answer is going to involve rather complicated and advanced code – beyond anything

we want to explore in this class.

Can the student’s name have any spaces or special characters? Not really.

Can the fields be separated by more than one space? You should check this through experiments.

Test Case

Input

Expected Output

1

1 1 1

a

Average for a is 1.00

2 2 2

b

Average for b is 2.00

100 200 300 c

Average for c is 200.00

-1 -2 -3 d

Average for d is -2.00

10 20 30 e

Average for e is 20.00

2

90.0

80.0

100.0 John

Average for John is 90.00

80.0

70.0

90.0 Jim

Average for Jim is 80.00

70.0

100.0

100.0 Joe

Average for Joe is 90.00

100.0 95.0

91.0 Sally

Average for Sally is 95.33

30.0

54.0

68.0 Sam

Average for Sam is 50.67

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Pseudocode

  • This program will calculate the average

  • of 3 exams for 5 students

  • Declare variables

Declare StudentName as String

Declare ExamValue, Sum, Avg as Float

// Loop through 5 Students

For (students=0; students <5 ; students++)

    • reset Sum to 0 Set Sum =0.0

Print “Enter 3 grades and student Name”

  • Nested Loop for Exams

For (exams=0; exams < 3; exams++)

Print “Enter exam grade: \n”

Input ExamValue

Set Sum = Sum + ExamValue

End For

Set Avg = Sum/3.0

Input StudentName

Print “Average for “ + StudentName + “ is “ + Avg

End For

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C Code

The following is the C Code that will compile in execute in the online compilers.

  • C code

  • This program will calculate the average

  • of 3 exams for 5 students.

  • Developer: Faculty CMIS102

  • Date: Jan 31, XXXX

#include <stdio.h>

int main(void) {

  • variable declarations: char name [100];

float sum, grade, average; int students, exams;

  • loop through 5 students

for (students = 0; students < 5; students++) { printf (“Enter 3 grades and student name: “); sum = 0;

for (exams = 0; exams < 3; exams++) {

// float uses %f, double uses %lf scanf (“%f”, &grade);

sum = sum + grade;

} // end for each exam

average = sum / 3;

scanf (“%s”, name);

printf (“Average for %s is %.2f\n”, name, average);

} // end for each student printf(“… Bye …\n”); return 0;

} // end main

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Screen Shots:

Setting up the code panel in repl.it:

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Note the Student and ExamValues for this run were:

90.0 80.0 100.0 John 80.0 70.0 90.0 Jim 70.0 100.0 100.0 Joe 100.0 95.0 91.0 Sally 30.0 54.0 68.0 Sam

You can change these values to any valid integer values to match your test cases.

Results from running the programming at repl.it

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Learning Exercises for you to complete

  1. Demonstrate you successfully followed the steps in this lab by preparing screen captures of you running the lab as specified in the Instructions above.

  1. Modify the code to be able to input any number of students (i.e. the loop is controlled by the user input). You will still only have 3 exams for each student. Support your experimentation with screen captures of executing the new code.

  1. Prepare a new test table with at least 3 distinct test cases listing input and expected output for the new code you created allowing the input of any number of students.

  1. What is the line of code doing?

char StudentName[100];

(Hint: We haven’t covered arrays, but a String can be thought of as an array of characters) ?

  1. What would happen if you moved the Set Sum = 0.0 from inside the for loop to right after the declaration. For example:

// Declare variables

Declare StudentName as String

Declare ExamValue, Sum, Avg as Float

  • Initialize Sum Set Sum = 0.0;

Support your experimentation with screen captures of executing the new code.

  1. (Optional and challenging) How could you modify the input protocol and the code to allow the user to enter more than 3 grades per student?

  1. (Optional and even more challenging) How could you modify this code to allow the user to enter a different number of grades for each student?

  1. (Optional and even more challenging) How could you modify this code to allow the user to enter a weight for each grade, as in Lab 5?

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Grading guidelines

Submission

Points

Demonstrates the successful execution of this Lab within an

30

online compiler. Provides supporting screen captures.

Modifies the code to be able to input any number of students

20

(i.e. the loop is controlled by the user input). You will still only

have 3 exams for each student. Supports your

experimentation with screen captures of executing the new

code.

Prepares a new test table with at least 3 distinct test cases

10

listing input and expected output for the new code you

created allowing the input of any number of students.

Describes what the char array line is doing.

10

Describes what would happen if you moved the Set Sum = 0.0

20

from inside the for loop to right after the declaration. Be sure

to provide screen captures to document your analysis and

results.

Document is well-organized, and contains minimal spelling

10

and grammatical errors.

Total

100

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