In programming, how do static and dynamic memory allocation differ, and which examples illustrate each type correctly?

Introduction / Context:
Memory allocation is a fundamental concept in languages like C and C++. Programmers frequently choose between static and dynamic allocation depending on the problem. Confusion often arises about where each kind of memory lives and when it is reserved. This question tests your understanding of the conceptual difference and common examples of static versus dynamic allocation.

Given Data / Assumptions:

• Static allocation is associated with compile time decisions about size and lifetime.
• Dynamic allocation is associated with runtime decisions made by the program while it runs.
• Languages such as C and C++ provide functions like malloc free and operators like new delete for dynamic allocation.
• Global variables and local arrays with fixed size are common examples of static allocation.

Concept / Approach:
Static memory allocation occurs when the compiler decides the size and location of data at compile time. Examples include global variables, static variables inside functions, and fixed size arrays allocated on the stack. Their memory is reserved in advance and remains allocated for the whole program run or for the duration of the block. Dynamic memory allocation occurs when the program explicitly requests memory from the heap at runtime using calls such as malloc, calloc, or new. The exact amount can depend on user input or other runtime conditions, and the program must later release the memory with free or delete to avoid leaks.

Step-by-Step Solution:
Step 1: Consider a declaration like int a[100]; at global scope or inside main with fixed size. The compiler knows at compile time that one hundred integers are required. Step 2: Recognise that such memory is reserved either in the static storage area or on the stack before the program or function executes, which is static allocation. Step 3: Now consider code like int n; scanf("%d", &n); int* p = (int*)malloc(n * sizeof(int)); where n is chosen at runtime. Step 4: Here, malloc requests a block of n integers from the heap at runtime. This is dynamic allocation and can succeed or fail depending on available memory. Step 5: To be correct, dynamic memory must be released later using free(p) or delete p, otherwise a memory leak occurs.

Verification / Alternative check:
If you try to write int a[n]; in old style C where n is not a compile time constant, the compiler may reject it or treat it as a variable length array. In contrast, using malloc with n always works when enough heap memory exists. This shows that static allocation expects sizes known at compile time, while dynamic allocation adapts at runtime. Tooling and debuggers also label these regions differently as stack or heap, confirming the conceptual difference.

Why Other Options Are Wrong:
Option b incorrectly states that static allocation uses only heap, which is the opposite of normal usage. Option c claims that static and dynamic allocation belong to different language paradigms, which is not accurate; both appear in many languages. Option d confuses memory allocation in RAM with disk storage, which is outside the scope of typical static versus dynamic allocation discussions.

Common Pitfalls:
A common mistake is assuming that dynamic allocation is always better because it is flexible, forgetting that it introduces complexity and risk of leaks. Another is assuming that stack memory is always safer without considering stack size limits. Good design uses static allocation for fixed structures and dynamic allocation for variable size or long lived objects.

Final Answer:
Static and dynamic allocation differ in timing and location, and the correct statement is that static allocation reserves memory at compile time for fixed size objects, while dynamic allocation reserves memory at runtime using new or malloc based on current needs.