C programming — spot the error related to forward declarations and prototypes.\n\n#include<stdio.h>\n#include<string.h>\n\nvoid modify(struct emp*); /* prototype uses struct emp before its declaration /\n\nstruct emp\n{\n char name[20];\n int age;\n};\n\nint main()\n{\n struct emp e = {"Sanjay", 35};\n modify(&e);\n printf("%s %d", e.name, e.age);\n return 0;\n}\n\nvoid modify(struct emp p)\n{\n p->age = p->age + 2;\n}\n\nWhat is the correct assessment for standard C?

Introduction / Context:
This question examines how C handles tags (struct names) with respect to declarations and prototypes. Using a structure tag in a function prototype before the tag is declared requires at least a forward declaration of the tag.

Given Data / Assumptions:

• The function prototype void modify(struct emp); appears before struct emp is declared.
• No forward declaration (struct emp;) precedes the prototype.

Concept / Approach:
In C, identifiers must be declared before use. A struct tag introduces a distinct namespace. To mention struct emp in a prototype prior to the full definition, you must forward declare it: struct emp; After that, the prototype may use struct emp safely, and the full definition can follow.

Step-by-Step Solution:

Verification / Alternative check:
Adding struct emp; makes the code compile; modify then increments age by 2 and the program prints "Sanjay 37".

Why Other Options Are Wrong:

• Structure definition error: The definition itself is fine.
• No error: Violates declaration-before-use for the tag in standard C.
• Linker error: The issue is purely compile-time, not linking.

Common Pitfalls:
Assuming prototypes can reference undeclared tags; forgetting that struct tags form their own namespace and need forward declarations when used early.

Final Answer:
Error: in prototype declaration unknown struct emp