In programming language theory, which statement best captures what a programming language does with respect to computer instructions and machine dependence?

Introduction / Context:
Programming languages are formal systems used to express computations. They define how instructions are written (syntax) and what they mean (semantics), enabling compilers or interpreters to translate or execute programs on various machines. The relationship to specific hardware varies: some languages are highly portable and abstract; others are tailored to particular architectures or environments.

Given Data / Assumptions:

• Programming languages specify constructs like expressions, statements, types, and control flow.
• Compilers/interpreters map high-level programs to machine code or bytecode.
• Machine dependence is not absolute; it depends on language design and implementation.

Concept / Approach:

The primary function of a programming language is to define the form of the instruction—what can be said and how to say it precisely—along with the meaning when executed. Portability and dependence are properties of implementations and language abstractions. For example, C exposes low-level details that can vary across platforms (sizes, endianness), while Java or Python abstract more and target virtual machines or interpreters to reduce dependence.

Step-by-Step Solution:

Verification / Alternative check:

Language specifications (for example, the C standard, the Java Language Specification) define syntax/semantics, while compilers handle mapping to machines, confirming the core role of a language.

Why Other Options Are Wrong:

“Always machine dependent” and “never machine dependent” are absolutes contradicted by real-world variance.

“All of the above” cannot be true because the preceding options conflict.

Common Pitfalls:

Confusing the language definition with specific compiler behavior or platform ABI details; portability depends on both design and implementation.

Final Answer:

A programming language defines the form and structure (syntax and semantics) of instructions