Const object initialization rule in C: diagnosing assignment after declaration\n\n#include<stdio.h>\n\nint main()\n{\n const int x; /* uninitialized /\n x = 128; / attempted assignment after declaration */\n printf("%d\n", x);\n return 0;\n}

Introduction / Context:
This question evaluates understanding of const object initialization in C. A const object must be initialized at the point of its definition; further assignments are not allowed.

Given Data / Assumptions:

• x is declared as const int without an initializer.
• Later, x = 128 attempts to assign a new value.
• Standard C rules apply.

Concept / Approach:
Declaring const int x; creates a read-only object. Because it cannot be assigned to after declaration, you must initialize it immediately, e.g., const int x = 128;. Attempting to assign later violates const, producing a compile-time error.

Step-by-Step Solution:
Parse declaration: const int x; → needs initializer to set value.Line x = 128; → illegal: assignment to const object.Fix by writing const int x = 128; and removing the later assignment.

Verification / Alternative check:
Compile both versions: the incorrect one fails; the corrected one compiles and prints 128.

Why Other Options Are Wrong:
(a) “unknown data type” is false—const int is valid. (c) “stack overflow” is irrelevant. (d) claims no error, which is incorrect.

Common Pitfalls:
Believing const only prevents taking the address or only applies to pointer targets; assuming you can “set once later.”

Final Answer:
Error: const variable have been initialised when declared.