INTERVIEW QUESTIONS C DYNAMIC MEMORY ALLOCATION IN C DETAILS

Question: What is the heap?

Answer: The heap is where malloc(), calloc(), and realloc() get memory.

Getting memory from the heap is much slower than getting it from the stack. On the other hand, the heap is much more flexible than the stack. Memory can be allocated at any time and deallocated in any order. Such memory isn’t deallocated automatically; you have to call free().

Recursive data structures are almost always implemented with memory from the heap. Strings often come from there too, especially strings that could be very long at runtime. If you can keep data in a local variable (and allocate it from the stack), your code will run faster than if you put the data on the heap. Sometimes you can use a better algorithm if you use the heap—faster, or more robust, or more flexible. It’s a tradeoff.

If memory is allocated from the heap, it’s available until the program ends. That’s great if you remember to deallocate it when you’re done. If you forget, it’s a problem. A “memory leak” is some allocated memory that’s no longer needed but isn’t deallocated. If you have a memory leak inside a loop, you can use up all the memory on the heap and not be able to get any more. (When that happens, the allocation functions return a null pointer.) In some environments, if a program doesn’t deallocate everything it allocated, memory stays unavailable even after the program ends.

The heap is where malloc(), calloc(), and realloc() get memory.

Getting memory from the heap is much slower than getting it from the stack. On the other hand, the heap is much more flexible than the stack. Memory can be allocated at any time and deallocated in any order. Such memory isn’t deallocated automatically; you have to call free().

Recursive data structures are almost always implemented with memory from the heap. Strings often come from there too, especially strings that could be very long at runtime. If you can keep data in a local variable (and allocate it from the stack), your code will run faster than if you put the data on the heap. Sometimes you can use a better algorithm if you use the heap—faster, or more robust, or more flexible. It’s a tradeoff.

If memory is allocated from the heap, it’s available until the program ends. That’s great if you remember to deallocate it when you’re done. If you forget, it’s a problem. A “memory leak” is some allocated memory that’s no longer needed but isn’t deallocated. If you have a memory leak inside a loop, you can use up all the memory on the heap and not be able to get any more. (When that happens, the allocation functions return a null pointer.) In some environments, if a program doesn’t deallocate everything it allocated, memory stays unavailable even after the program ends. Source: CoolInterview.com

Heap is the term used for the memory allocation unit in C. In C++ memory allocation is done from "The Free Store". There is just difference of terminology.

Memory allocation takes place in C from heap.

Whenever u call malloc, calloc or realloc in C the memory is allocated from heap.
Memory allocated as such must be deallocated using free. Source: CoolInterview.com

In the process address space a region of memeory reserved is called heap. Memory can be allocated from the heap using malloc(),calloc() or realloac() functions which remains available until the program ends. If you dont deallocate this memory before program ends can lead to memory leak. Source: CoolInterview.com

When you want to allocate memory / de-allocate memory dynamically one will use heap memory. The existance of memory region is depend on programmer's use how long programmer want that memory. Once you done with that memory you can de-allocate the memory, so that memory can be allocated for some other purposes. Source: CoolInterview.com

I am a Govt employee so I cannot able to manage my PGDCA classes, that's why I want to study materials for PGDCA Course. I am doing this course from Dibrugarh University, Assam, India. How I could benifit please reply----- Source: CoolInterview.com

heap is a data structur to implement
priority queues.This is the most efficent way Source: CoolInterview.com

Heap is part of stack memory,which can grow and shrink during run time.Memmory is allocated in heap by calling malloc(),calloc(),realloc() functions.For all parts of memory except heap,memory get at compilation time is same at run time.It cannot change.But heap can do it Source: CoolInterview.com

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