41 lines
1.5 KiB
Markdown
41 lines
1.5 KiB
Markdown
---
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id: 18bl
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title: Heap_memory
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tags: [memory, C]
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created: Saturday, April 20, 2024
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---
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# Heap memory
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Along with [[Stack_memory|Stack memory]], programs make use of _heap memory_
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during runtime.
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Heap memory does not use a standardised data structure and can be accessed from
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any point within the program.
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Whereas stack memory with it's LIFO structure has memory management built-in
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when programs allocate memory from the heap they must manually deallocate it
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when it is no longer required. This process of "freeing memory" is known as
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_garbage collection_. In a language like C, this is the explicit concern of the
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programmer and is not abstracted away. Failure to properly manage garbage
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collection is what causes [[Memory_leaks]].
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Heap memory is used in combination with the stack since a given heap memory
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allocation address is stored as a stack variable during runtime. It points to
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the heap memory address whilst not being that memory itself.
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Here is an example of managing heap memory allocation in C:
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```c
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void * data;
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data = malloc(512)
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```
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The first line assigns a special _pointer_ variable (indicated by `void *`
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rather than `int` or `str`) . This is a variable only holds a memory address.
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The `malloc` method requests 512 bytes that it wants to assign to the `data`
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variable. It will return the address of the first byte in the newly allocated
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memory. `data` will then refer to the address on the stack that holds the
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address allocation on the heap.
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## Related notes
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