Which is a simple switch-case that prints a message for 0, 1, or default?

Which is a simple switch-case that prints a message for 0, 1, or default?

• A. switch (val) { case 0: /* print zero */; break; case 1: /* print one */; break; default: /* print other */; }
• B. switch (val) { case 0: /* print zero */; case 1: /* print one */; break; default: /* print other */; }
• C. switch (val) { if (val == 0) /* print zero */; }
• D. switch (val) { case 0: print("zero"); case 1: print("one"); default: print("other"); }

Answer: (A)

The key idea is preventing fall-through in a switch by using explicit case labels paired with breaks, and providing a default for anything not listed. The correct option maps 0 and 1 to their own blocks and then stops with a break after each one, while the default handles everything else. This guarantees that for a given value one and only one message is printed. For a value of 0, the code enters the case for 0, executes the print, and then hits the break, so it won’t continue into the 1-case or default. The same logic applies to a value of 1. Any other value falls through to the default, printing the “other” message. This precise control over flow is what makes this approach reliable. The other options fail because they either omit a necessary break, causing unintended fall-through (so a 0 could also print the 1 message, etc.), or omit the proper switch-case structure altogether (using an if inside a switch isn’t how switch-case is meant to be used), or still lack breaks and would print multiple messages for a single input.

The key idea is preventing fall-through in a switch by using explicit case labels paired with breaks, and providing a default for anything not listed. The correct option maps 0 and 1 to their own blocks and then stops with a break after each one, while the default handles everything else. This guarantees that for a given value one and only one message is printed.

For a value of 0, the code enters the case for 0, executes the print, and then hits the break, so it won’t continue into the 1-case or default. The same logic applies to a value of 1. Any other value falls through to the default, printing the “other” message. This precise control over flow is what makes this approach reliable.

The other options fail because they either omit a necessary break, causing unintended fall-through (so a 0 could also print the 1 message, etc.), or omit the proper switch-case structure altogether (using an if inside a switch isn’t how switch-case is meant to be used), or still lack breaks and would print multiple messages for a single input.