Question

[15 marks] Suppose that students enrolled in one course are required to take four tests, and each student’s final grade for this course is the average of his/her grades of these four tests. This question asks you to write a program that can be used to compute the lowest final grade, highest final grade and the average final grade.

General Requirements: Use a5q1.c as the name of your C source code file. We will use the following command on bluenose to compile your program:

gcc -std=c99 -o grades a5q1.c

Your program should NOT print anything to prompt for user input. As many numbers have to be read from stdin to test your programs, you are expected to use input redirection to read the input from a file. More precisely, you can run your program using the following command:

./grades < grades.1
In the above command, the file grades.1 is a plain text file of the following format:

(a) The first line has one integer. If this integer is 1, 2, or 3, then you are asked to compute the lowest, highest, or average final grade, respectively.

(b) The second line also has one integer, and it is the number of students.

(c) Starting from the third line, each line stores the grades of one student. More precisely, it contains four integers (separated by spaces) in the range [0,100], which are grades this student obtained in the four required tests.

For example, consider the following input file:

1
3
90 80 77 79
65 78 81 88
92 91 95 93

It means that you are asked to find out the lowest final grade. There are three students. The first student got 90, 80, 77, 79 as grades in his four tests, and so on.

Your program should then compute the lowest, highest or average final grade according to the first integer read, and print the result as a floating point number, keeping two digits after the decimal point. A trailing newline is also printed. For this input, the first student’s final grade is (90 + 80 + 77 + 79)/4 = 78, which is the lowest among the three students. Thus the output is:

78.00

Error Handling: You can assume that user input contains integers only. However, your program should print an appropriate error message and terminate in each of the following cases:

(a) The first number of the input is not 1, 2, or 3 (i.e., an incorrect option is given). (b) The second number is not positive.

2

(c) Each grade in the input is not an integer in the range [0, 100].
If there is more than one problem with user input, your program just has to detect one

of them.

Testing: To test your program automatically, we will use it as a UNIX filter.
For the example above, we will test it using the following command in the directory

containing the executable program (assume that grades.1 is the input file)

  ./grades < grades.1

To help you make sure that the output format of your program is exactly what this questions asks for, several files are provided in the following folder on bluenose to show how exactly your program will be automatically tested:

  /users/faculty/prof2132/public/a5test/

In this folder, open the file a5q1test to see the commands used to test the program with three test cases. The output files, generated using output redirection, are also given.

To check whether the output of your program on any test case is correct, redirect your output into a file, and use the UNIX utility diff (learned in Lab 3) to compare your output file with the output file in the above folder, to see whether they are identical.

Since these output files are given, we will apply a penalty to any program that does not strictly meet the requirement on output format. This includes the case in which your output has extra spaces, or has a missing newline at the end.

We will use different test cases to test your program thoroughly. Therefore, construct a number of test cases to test your program thoroughly before submitting it.

Hint: You are not required to organize your program using functions yet for this assignment (it will be required for Assignment 6). However, if you do use functions, then, when handling errors, you may need to terminate the program when a function that is not main is being executed. Read page 203 of the text book to find out how to use the exit function to do this.

Answer 1

Given below is the code for the question.

1. Save the code in a file name a5q1.c

2. Compile using
gcc -std=c99 -o grades a5q1.c

3. Save the following input lines in a file named grade1.txt
1
3
90 80 77 79
65 78 81 88
92 91 95 93

4. Run the program using input redirection from file
./grades < grades1.txt

Please do rate the answer if it helped. Thank you.

#include <stdio.h>
int main()
{
  
int statsChoice;
int numStudents;
float grade, final, lowest = -1, highest = 0, average = 0;
int error = 0;
int i, j;
  
//get the choice 1, 2, 3 which calcualation needs to be done lowest, highest or average
scanf("%d", &statsChoice);
if(statsChoice < 1 || statsChoice > 1)
{
printf("Invalid choice! Should be 1, 2 or 3\n");
}
else
{
//get the number of students
scanf("%d", &numStudents);
if(numStudents <= 0)
{
printf("The number of students should be positive\n");
}
else
{
for(i = 1; !error && i <= numStudents; i++) //for each student
{
final = 0;
for(j = 1; !error && j <= 4; j++) //get 4 grades
{
scanf("%f", &grade);
if(grade < 0 || grade > 100)
{
printf("Grades should be in the range of [0,100]\n");
error = 1;
}
else
{
final += grade;
}
}
  
final /= 4;
  
switch(statsChoice)
{
case 1: //find lowest grade
if(lowest == -1 || final < lowest) //if lowest is not yet set or this new grade is lesser
lowest = final;
break;
case 2: //find highest grade
if(final > highest) //this new grade is higher
highest = final;
break;
case 3:
average += final;
break;

}
}
  
  
//display the output
  
if(statsChoice == 1)
printf("%.2f\n", lowest);
else if(statsChoice == 2)
printf("%.2f\n", highest);
else if(statsChoice == 3) //average calculation?
{
average /= numStudents;
printf("%.2f\n", average);
}
}
}
return 0;
}

--------output--------

amoeba-2:Test1 rajis gcc -std-c99 -o grades a5q1.c amoeba-2:Test1 rajis ./grades < grades1.txt 78.00 amoeba-2:Testl rajis|