C Object Instantiation: Stack vs. Heap: `new` or Not `new`?

Instantiating Objects: With or Without New

When creating objects in C , programmers can use either the "new" operator or instantiate them directly without it. While both approaches create objects, they differ in several key aspects.

Without New

Instantiating an object without "new" directly reserves memory for it in the current scope. This is typically done on the stack and results in an object with an automatic lifetime. The object is created and destroyed automatically within the scope it was defined.

For example:

Time t(12, 0, 0); // t is a Time object

In the code above, the "Time" object "t" is created on the stack and its lifetime is bound to the current scope.

With New

Using "new" to instantiate an object allocates memory for it dynamically on the heap. This allows the object to be created and destroyed explicitly when its lifespan ends. The pointer "t" stores the heap address of the object.

For example:

Time* t = new Time(12, 0, 0); // t is a pointer to a dynamically allocated Time object

Here, the pointer "t" is assigned the heap address of the newly created "Time" object. The object's lifetime is independent of scope and persists until the "delete" operator is used to free its memory.

Key Differences

• Memory Allocation: Objects created without "new" allocate memory on the stack, while "new" allocates memory on the heap.
• Lifetime: Objects instantiated without "new" have an automatic lifetime, while objects created with "new" have a dynamic lifetime and must be manually deleted.

It's important to note that these differences are implementation-specific, as the C standard does not explicitly define stack and heap behavior. However, in most practical implementations, stack memory is used for automatic objects, and heap memory is used for dynamic objects.

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