In the following C program that uses a function pointer, what is the error? void fun() { printf("Loud and clear"); } int main() { int (*p)() = fun; (*P)(); return 0; }

Introduction / Context:
This question checks understanding of case sensitivity in C, function pointers, and correct identifier usage. It presents code that attempts to call a function through a pointer but introduces a subtle error in the spelling of the pointer variable.

Given Data / Assumptions:

• There is a function fun that prints a message.
• A function pointer p is declared and initialized as int (*p)() = fun;.
• The code attempts to call (*P)(); instead of (*p)();.

Concept / Approach:
C is a case sensitive language. This means that identifiers such as p and P are distinct names. Declaring int (*p)() = fun; introduces a pointer variable named p, but it does not introduce any variable named P. When the compiler encounters (*P)();, it will look for a declaration of P and will not find one, which results in an error about an undeclared identifier.

Step-by-Step Solution:
Step 1: The line int (*p)() = fun; correctly declares and initializes a function pointer p that can point to fun.Step 2: The intended call to the function through the pointer should use p, for example p(); or (*p)();.Step 3: The code instead writes (*P)(); with an uppercase P.Step 4: Since P has never been declared, the compiler will report an error such as "P undeclared" or "use of undeclared identifier P".

Verification / Alternative check:
If you correct the code to use (*p)(); or simply p();, the program compiles and runs, printing "Loud and clear". This confirms that the only real issue is the mistaken use of P instead of p.

Why Other Options Are Wrong:
Option B is incorrect because function pointers can be assigned and int (*p)() = fun; is valid C.Option C is false because calling functions through pointers is a standard and supported feature in C.Option D is incorrect in modern C; int main() is the standard signature and void main is not recommended.

Common Pitfalls:
Case sensitivity errors are common in C, especially when variable names differ only in capitalization. Careful, consistent naming and the use of compiler warnings help catch such mistakes quickly.

Final Answer:
The error is that The identifier P in the call (*P)() has not been declared; C is case sensitive, so P is different from the declared pointer p.