Capítulo 3 - Novo exemplo

Summary

This video script explains the technique of desk testing to debug and validate a program that swaps the values of two variables, A and B. Initially, the program contains an error where both variables end up with the same value due to overwriting. The solution involves introducing a third variable, `aux`, to preserve the original value of A during the swap. Through a detailed desk test, the corrected program produces the expected output, with A and B swapped correctly. The script highlights how desk testing can be used to identify and fix logical errors before running the code.

Takeaways

• 😀 The algorithm aims to swap the values of two variables, A and B.
• 😀 The test de mesa (test table) technique is used to simulate and track the program’s execution step by step.
• 😀 The initial algorithm fails because it overwrites the value of A when trying to assign the value of B to it.
• 😀 The result of the incorrect algorithm is that both variables, A and B, end up with the same value, which is an error.
• 😀 The test de mesa helps identify this issue by showing the steps and changes in variable values in a table format.
• 😀 To fix the algorithm, a third variable (C) is introduced to preserve the original value of A before it is overwritten.
• 😀 The corrected algorithm first stores the value of A in variable C, then assigns the value of B to A, and finally assigns the value of C (original A) to B.
• 😀 After the fix, the correct swap is achieved with A = 3 and B = 12, as expected.
• 😀 The test de mesa method is valuable for debugging and ensuring the correctness of algorithms before execution.
• 😀 The test de mesa technique can be applied to programs with various structures, such as sequences, selections, and other control flow structures.

Q & A

What is the main objective of the algorithm described in the script?

The main objective of the algorithm is to read two numbers, A and B, and swap their values, displaying the results after the swap.

What error was identified in the original solution for swapping the values of A and B?

The error was that after the swap, both A and B ended up with the same value because one variable's value was overwritten before it could be transferred.

How can the error in the original solution be corrected?

The error can be corrected by introducing a third variable (aux) to temporarily store one of the values, preventing it from being overwritten during the swap.

What is the role of the third variable (aux) in the corrected solution?

The third variable (aux) temporarily holds the original value of A before it is overwritten by the value of B, allowing the swap to be performed correctly.

What is the outcome of running the corrected solution with A = 12 and B = 3?

After running the corrected solution, the final values of the variables are A = 3 and B = 12.

What is the importance of desk testing in this scenario?

Desk testing is important because it simulates the program's execution and helps identify errors in logic before running the program on a computer.

How does desk testing help in debugging a program?

Desk testing helps by allowing a programmer to track the flow of variables and ensure the logic is correct, identifying errors before actual execution.

In what type of program structures can desk testing be applied?

Desk testing can be applied to programs with various structures, including simple sequential, selection, and even more complex structures like loops and function calls.

Why is it necessary to use a third variable for swapping two values in the provided algorithm?

A third variable is necessary to hold one value temporarily, as direct assignment of one variable's value to another would overwrite the original value, leading to incorrect results.

What was the expected output after the fix, and how was it achieved?

The expected output after the fix is A = 3 and B = 12. This was achieved by using the third variable to correctly swap the values without overwriting them.