ProgramGuru

Choose Between Outcomes

Choose Between Outcomes

An if-else decision evaluates a condition and runs one branch.

The school can display a pass result while keeping instructions after the decision unconditional.

Before this lesson, review Store Student Names when needed.

What you’ll learn

  • Use if else to choose Between Outcomes.
  • Explain how the complete example produces Pass.
  • Make the practice change and explain why the result changes or stays the same.

Follow a complete C++ example

The school can display a pass result while keeping instructions after the decision unconditional.

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>

int main()  {
  int marks = 72;
  if (marks >= 50)  {
    std::cout << "Pass" << '\n';
  }
  else  {
    std::cout << "Practise" << '\n';
  }
  return 0;
}

Expected output

Pass
Run in C++ compiler →

Connect the code to its result

C++17 · source used in this explanation

#include <iostream>

int main()  {
  int marks = 72;
  if (marks >= 50)  {
    std::cout << "Pass" << '\n';
  }
  else  {
    std::cout << "Practise" << '\n';
  }
  return 0;
}

Expected output

Pass

An if-else decision evaluates a condition and runs one branch. The school can display a pass result while keeping instructions after the decision unconditional.

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 Pass. In this example, distinguish what the program calculates or changes from what it actually displays.

Choose Between Outcomes: cause and effect

  1. Operation

    An if-else decision evaluates a condition and runs one branch.

  2. Effect on school data

    The school can display a pass result while keeping instructions after the decision unconditional.

  3. Observed result

    The program displays these lines after the shown operations.

    Pass
Conceptual relationship for the actual program above; this visual does not execute C++.

Important mistakes and boundaries

C++ accepts contextual conversions to bool, so an accidental assignment in a condition can compile. Prefer clear comparisons and heed warnings.

Change the school example

C++17 · edit this complete example

#include <iostream>

int main()  {
  int marks = 72;
  if (marks >= 50)  {
    std::cout << "Pass" << '\n';
  }
  else  {
    std::cout << "Practise" << '\n';
  }
  return 0;
}

Your task: Use marks 40. 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: Use marks 40. Only Practise prints.

An if-else decision evaluates a condition and runs one branch. The school can display a pass result while keeping instructions after the decision unconditional.

C++ accepts contextual conversions to bool, so an accidental assignment in a condition can compile. Prefer clear comparisons and heed warnings.

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>

int main()  {
  int marks = 40;
  if (marks >= 50)  {
    std::cout << "Pass" << '\n';
  }
  else  {
    std::cout << "Practise" << '\n';
  }
  return 0;
}

Expected output

Practise
Run in C++ compiler →

Check your understanding

C++17 · original program for this question

#include <iostream>

int main()  {
  int marks = 72;
  if (marks >= 50)  {
    std::cout << "Pass" << '\n';
  }
  else  {
    std::cout << "Practise" << '\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

Pass

An if-else decision evaluates a condition and runs one branch. The school can display a pass result while keeping instructions after the decision unconditional. C++ accepts contextual conversions to bool, so an accidental assignment in a condition can compile. Prefer clear comparisons and heed warnings.

What to remember

An if-else decision evaluates a condition and runs one branch. C++ accepts contextual conversions to bool, so an accidental assignment in a condition can compile. Prefer clear comparisons and heed warnings.

Useful connections: Store Student Names, 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.

    Next lesson: Order Grade Rules →