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Build a Complete Student Report

Build a Complete Student Report

Combine records, a vector, validation, functions and a summary into one report.

Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted.

Before this lesson, review Separate Declarations and Definitions when needed.

What you’ll learn

  • Use student report project to build a Complete Student Report.
  • Explain how the complete example produces Invalid: Saira → Average: 76.
  • Make the practice change and explain why the result changes or stays the same.

Follow a complete C++ example

Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted.

Read the declarations above main before tracing its statements. Each declared name supplies the value, type or operation used later. The std:: prefix selects a name from the standard library, and cout << sends a value to the output stream.

C++17 · main.cpp · complete program

#include <iostream>
#include <string>
#include <vector>

struct Student  {
  std::string name;
  int marks;
}
;
int main()  {
  std::vector<Student> students {
    {
      "Diya", 72
    }
    ,  {
      "Aarav", 80
    }
    ,  {
      "Saira", 101
    }
  }
  ;
  int total = 0;
  int count = 0;
  for (const Student& student : students)  {
    if (student.marks < 0 or student.marks > 100)  {
      std::cout << "Invalid: " << student.name << '\n';
      continue;
    }
    total += student.marks;
    ++count;
  }
  if (count > 0)  {
    std::cout << "Average: " << static_cast<double>(total) / count << '\n';
  }
  return 0;
}

Expected output

Invalid: Saira
Average: 76
Run in C++ compiler →

Connect the code to its result

C++17 · source used in this explanation

#include <iostream>
#include <string>
#include <vector>

struct Student  {
  std::string name;
  int marks;
}
;
int main()  {
  std::vector<Student> students {
    {
      "Diya", 72
    }
    ,  {
      "Aarav", 80
    }
    ,  {
      "Saira", 101
    }
  }
  ;
  int total = 0;
  int count = 0;
  for (const Student& student : students)  {
    if (student.marks < 0 or student.marks > 100)  {
      std::cout << "Invalid: " << student.name << '\n';
      continue;
    }
    total += student.marks;
    ++count;
  }
  if (count > 0)  {
    std::cout << "Average: " << static_cast<double>(total) / count << '\n';
  }
  return 0;
}

Expected output

Invalid: Saira
Average: 76

Combine records, a vector, validation, functions and a summary into one report. Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted.

Trace the result: Read the complete program below from its starting values to the output operations. Each std::cout statement displays the value supplied at that point; \n begins the next line. The resulting lines, in order, are Invalid: Saira → Average: 76. In this example, distinguish what the program calculates or changes from what it actually displays.

Build a Complete Student Report: cause and effect

  1. Operation

    Combine records, a vector, validation, functions and a summary into one report.

  2. Effect on school data

    Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted.

  3. Observed result

    The program displays these lines after the shown operations.

    Invalid: Saira
Average: 76
Conceptual relationship for the actual program above; this visual does not execute C++.

Important mistakes and boundaries

This is an in-memory teaching report. It does not add persistent storage, Unicode normalization, authentication or a production grading policy.

Change the school example

C++17 · edit this complete example

#include <iostream>
#include <string>
#include <vector>

struct Student  {
  std::string name;
  int marks;
}
;
int main()  {
  std::vector<Student> students {
    {
      "Diya", 72
    }
    ,  {
      "Aarav", 80
    }
    ,  {
      "Saira", 101
    }
  }
  ;
  int total = 0;
  int count = 0;
  for (const Student& student : students)  {
    if (student.marks < 0 or student.marks > 100)  {
      std::cout << "Invalid: " << student.name << '\n';
      continue;
    }
    total += student.marks;
    ++count;
  }
  if (count > 0)  {
    std::cout << "Average: " << static_cast<double>(total) / count << '\n';
  }
  return 0;
}

Your task: Change Saira’s mark to 76. Before running your edited program, predict the new output and explain which stored value, condition or object changes. Keep the rest of the example intact.

Use the complete source repeated here; this task does not depend on remembering code from another section.

Worked answer and reasoning

Worked variation: Change Saira’s mark to 76. All three records qualify and their average remains 76.

Combine records, a vector, validation, functions and a summary into one report. Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted.

This is an in-memory teaching report. It does not add persistent storage, Unicode normalization, authentication or a production grading policy.

For a baseline run, save this source as main.cpp and use clang++ -std=c++17 -Wall -Wextra -pedantic main.cpp -o school, or equivalent g++ flags. Recompile after editing so that you run the updated executable.

The source and output below belong to the edited program. Compare them with the original example to see the consequence of this single change.

C++17 · worked variation · complete program

#include <iostream>
#include <string>
#include <vector>

struct Student  {
  std::string name;
  int marks;
}
;
int main()  {
  std::vector<Student> students {
    {
      "Diya", 72
    }
    ,  {
      "Aarav", 80
    }
    ,  {
      "Saira", 76
    }
  }
  ;
  int total = 0;
  int count = 0;
  for (const Student& student : students)  {
    if (student.marks < 0 or student.marks > 100)  {
      std::cout << "Invalid: " << student.name << '\n';
      continue;
    }
    total += student.marks;
    ++count;
  }
  if (count > 0)  {
    std::cout << "Average: " << static_cast<double>(total) / count << '\n';
  }
  return 0;
}

Expected output

Average: 76
Run in C++ compiler →

Check your understanding

C++17 · original program for this question

#include <iostream>
#include <string>
#include <vector>

struct Student  {
  std::string name;
  int marks;
}
;
int main()  {
  std::vector<Student> students {
    {
      "Diya", 72
    }
    ,  {
      "Aarav", 80
    }
    ,  {
      "Saira", 101
    }
  }
  ;
  int total = 0;
  int count = 0;
  for (const Student& student : students)  {
    if (student.marks < 0 or student.marks > 100)  {
      std::cout << "Invalid: " << student.name << '\n';
      continue;
    }
    total += student.marks;
    ++count;
  }
  if (count > 0)  {
    std::cout << "Average: " << static_cast<double>(total) / count << '\n';
  }
  return 0;
}
Before making the practice edit, what does the original C++17 program print?
Choose one answer. You can try again.

Answer and explanation

Invalid: Saira Average: 76

Combine records, a vector, validation, functions and a summary into one report. Each valid student contributes one mark to the total, while invalid records are reported rather than quietly counted. This is an in-memory teaching report. It does not add persistent storage, Unicode normalization, authentication or a production grading policy.

What to remember

Combine records, a vector, validation, functions and a summary into one report. This is an in-memory teaching report. It does not add persistent storage, Unicode normalization, authentication or a production grading policy.

Useful connections: Separate Declarations and Definitions, Give a Task a Name.

Language and design guidance: C++ Core Guidelines and C++ working draft. The draft describes an evolving language; these examples deliberately target C++17.

Reaching the recap and completing the quizzes are separate milestones.

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