Dereferencing a pointer-to-const bound to a const object: With const int x = 5; const int *ptrx = &x; what happens when executing *ptrx = 10; then printing x?

Introduction / Context:In C, a pointer declared as const int * is a pointer to a read-only integer. The qualifier applies to the pointed-to object as accessed through that pointer. Attempting to assign through such a pointer is forbidden and should trigger a compiler error, safeguarding program correctness by preventing unintended writes to protected data.

Given Data / Assumptions:

• const int x = 5;
• const int *ptrx = &x;
• Statement: *ptrx = 10; followed by printing x.

Concept / Approach:

• The expression *ptrx designates a non-modifiable lvalue because ptrx points to const-qualified int.
• Assigning a new value to a non-modifiable lvalue is illegal; compilers issue messages like 'assignment of read-only location'.
• Therefore, the program fails to compile at the assignment; no runtime output is produced.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• 5 or 10: imply successful execution, but the assignment will not compile.
• Garbage value: not applicable; the code does not run.
• Warning-only scenario: standards-compliant compilers treat this as an error when you attempt the assignment.

Common Pitfalls:

• Misunderstanding that const applies to the pointer vs the pointee; here, the pointee is const.
• Believing that casting away const makes it safe to write; it does not if the original object was defined const.

Final Answer: