How programs are compiled or interpreted in Intro to Computing - Practice Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main difference between a compiler and an interpreter?

Imagine you want to translate a book from one language to another. Which of the following best describes how a compiler and an interpreter work?

A A compiler translates the entire book at once before you read it; an interpreter translates the book sentence by sentence as you read.

B A compiler translates only the first chapter; an interpreter translates the whole book at once.

C A compiler translates the book into pictures; an interpreter translates it into sounds.

D A compiler reads the book aloud; an interpreter writes the book down.

💡 Hint

Think about when the translation happens: all at once or bit by bit?

A compiler translates the entire program into machine code before running it, like translating a whole book before reading. An interpreter translates and runs the program line by line, like translating sentence by sentence while reading.

❓ trace

intermediate

Trace the output of an interpreted program

Consider this simple program interpreted line by line. What will be printed?

Intro to Computing

x = 5
print(x)
x = x + 3
print(x)

A 5\n5

B 8\n8

C 8\n5

D 5\n8

💡 Hint

Follow the program line by line and note the value of x at each print.

The interpreter runs line by line: first x is 5, so it prints 5. Then x becomes 8, so it prints 8.

❓ Comparison

advanced

Which program runs faster and why?

Two programs do the same task. One is compiled, the other interpreted. Which runs faster and why?

A The interpreted program runs faster because it skips some code lines.

B Both run at the same speed because they do the same task.

C The compiled program runs faster because it is translated into machine code before running.

D The interpreted program runs faster because it translates code as it runs.

💡 Hint

Think about when the translation happens and how that affects speed.

Compiled programs run faster because the entire code is translated into machine code before execution, so the computer runs it directly. Interpreted programs translate code line by line during execution, which adds overhead and slows it down.

❓ identification

advanced

Identify the step where compilation happens in this flowchart

Look at the flowchart below describing how a program runs. Which step is the compilation step?

A Compiler

B Source Code

C Machine Code

D Execution

💡 Hint

The compiler is the tool that translates source code into machine code.

The compilation step is done by the compiler, which takes source code and produces machine code that the computer can execute.

🧠 Conceptual

expert

Why might a language use both compilation and interpretation?

Some programming languages use both compilation and interpretation. Why would this be done?

A Because the compiler cannot translate all code, so the interpreter finishes the job.

B To combine fast execution from compilation with flexibility from interpretation.

C To confuse programmers and make debugging harder.

D Because interpretation is always faster but less accurate than compilation.

💡 Hint

Think about the benefits of each method and how they might complement each other.

Languages like Java compile code into an intermediate form (bytecode) for speed, then interpret or just-in-time compile it for flexibility and platform independence.