Memory Management in C and C++

In this tutorial, let’s look into how memory is managed in C++

🗑️Architecture

️️This darchitecture shows the hierarchy of how the memory is stored and managed in a C or C++ program. For any C or C++, the data gets stores in this architecture similar to this. Let’s start from the bottom of the diagram.

• Text: This segment stores instruction that needs to be executed.
• Static/Global: This segment is used to store global variables. Once the execution of main( ) is over; the data stored in this segment is popped out.
• Heap: Used to allocate memory for dynamically allocated variables.
• Stack: Used to the store the function calls and it’s respective local variables.

Let’s take an example:

For the above CPP program, this is how the memory allocation will look like;

Once each function block is executed and returned with some value, the memory is popped out from the stack segment.

🔺Why Heaps?

Now, let’s see how Heap segments are used to store data. Heaps are dynamic in size. Hence they are used to allocated dynamic variables.

In C, the following functions are used to allocate dynamic memory to the variables and arrays.

• malloc( ) //memory allocation
• calloc ( ) //contiguous memory allocation
• realloc ( ) // memory reallocation
• dealloc ( ) // memory deallocation

In C++, the following operators are used

• new
• delete

Let’s see an example by dynamically allocating memory for a variable in C

For the above code; the function calls and local variables get pushed to the stack segment. The variable “p” points to the address (say 200). When checked in address 200 (in heap), we could find the value of p. This is how the heap works. Heaps can be used to create a memory block to store a value and point the address of the block to the respective pointer variable.

📓 Points to remember

• Heap segment is used for dynamic memory allocation.
• The size of the heap is dynamic and based on the user’s input.
• The stack is used for storing function calls and local variables
• The size of the stack depends on the “stackframe” generated while calling functions, also depends on the number of methods. It varies from OS and the compiler.
• Static/Global segment is used to store global variables. The text segment for instructions.