What will be the result of calling num[0] = 2 in the function func(const int num[])?

In the function definition func(const int num[]), the parameter num[] is defined as a pointer to a constant integer array. This means that the elements of the array are read-only within the scope of the function, and any attempt to modify the contents of the array is prohibited.

When executing num[0] = 2, you are attempting to assign a value to the first element of the array. However, since the array has been declared as constant, this assignment violates the rules of const correctness in C and C++. The compiler recognizes the assignment as an attempt to modify a constant value, which leads to a compile-time error.

This behavior is crucial in programming because it enforces the immutability of parameters that are meant to be constant. Such design helps ensure that certain data is protected from unintended modifications, thus enhancing the overall stability and reliability of the code.

In summary, trying to modify a constant array parameter leads to a compile-time error, confirming that this is the correct interpretation of the function's constraints regarding the immutability of input values.