Interpreter as a Program that Translates a Program Statement by Statement into Machine Language

Introduction:
In the context of computer programming, a computer program that translates a program statement by statement into machine language is called an interpreter. An interpreter reads and executes the program code line by line, translating each statement into machine language and immediately executing it.

Explanation:
Below are the details explaining why the correct answer is option 'D' - Interpreter:

1. Compiler:
- A compiler is a program that translates the entire source code of a program written in a high-level language into machine language all at once.
- It generates an executable file that can be run directly by the computer without the need for any further translation.
- Unlike an interpreter, a compiler does not execute the program directly; it only translates the code.

2. Simulator:
- A simulator is a program that models the behavior of a system or process.
- It is used to simulate real-world scenarios and analyze their outcomes.
- A simulator may or may not translate programs into machine language.

3. Translator:
- A translator is a general term used to refer to any program that converts one form of code or language into another.
- It can include both compilers and interpreters.
- However, in the context of the given question, a translator does not specifically refer to a program that translates a program statement by statement into machine language.

4. Interpreter:
- An interpreter is a program that directly executes the program code line by line, translating each statement into machine language and immediately executing it.
- It does not generate an executable file like a compiler does.
- The advantage of an interpreter is that it can provide immediate feedback and can be used for interactive programming.
- However, it may be slower than a compiled program as it translates and executes the code line by line.

Conclusion:
Based on the above explanation, the correct answer is option 'D' - Interpreter, as it accurately describes a computer program that translates a program statement by statement into machine language.