Questions tagged [memory-allocation]
The memory-allocation tag has no usage guidance.
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1answer
42 views
How does dynamic memory-allocation exactly work?
I have wondered about profane code. Assume we are running this code on any modern System like Unix/Linux/Mac/Windows. This code is C, but it should work with every language which is close to the ...
0
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1answer
35 views
How does the memory of a 64bit and 32bit processor work
In this article, the author states that a 64bit processor can theoretically reference 2^64 bytes of memory. What does he mean by this statement, or rather the word, reference?
Also, I visualize the ...
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0answers
11 views
Memory addressing
What does the following sentence mean?
"The 8085 micropressor has the capability of addressing 64KB of RAM?"
In general, what is the meaning of a CPU's ability to address a given amount of memory? ...
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0answers
6 views
Memory interfacing problem [duplicate]
I've learnt that the memory interfacing problem is used when we need to connect a memory that has lesser number of locations to a processor that has more address lines.
For eg. Connecting memory chips ...
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2answers
33 views
Random access memory and data
What kind of data is stored in the RAM when it is fresh out of manufacture?
Apart from certain basic instructions (if yes, what are they), are there numbers stored as well or are most of the memory ...
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0answers
21 views
Addresses with no memory allocated
I've read that a program can crash if it tries to access addresses with no memory allocated. But, how is it possible that an address has no memory allocated? When does it happen?
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2answers
44 views
How does a computer remember the address of a data variable in a program, in the main memory?
Suppose I write a program as below:
int main()
{
int a = 3;
int b = 4;
return 0;
}
Suppose the computer stores the address of 'a' as 0x00104. How does it ...
1
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1answer
30 views
Binary trees and preallocated nodes
I want to design a binary tree with preallocated nodes, in order to avoid calling malloc/free every time I want to insert/delete a node. The problem is I don't know ahead of time how many nodes the ...
1
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2answers
4k views
How is the formula for calculation in row/column major obtianed?
In my book, this formula is given for calculation of address of row major order's element $[I,J]$:
Address of $[I,J]$th element in row major order $= B + W[n(I-L_r)+ [J-L_c]]$
where B denotes base ...
1
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1answer
37 views
Allocating memory via Buddy Allocation
I'm trying to learn buddy allocation and whilst I think I understand the basics of it, there is one problem exercise with which I'm struggling with.
So I have an 8K block and I'm using buddy ...
2
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0answers
18 views
Sweeping integrated into memory allocation: Why only fixed size objects?
In our language design book, it is mentioned that GC sweep can be integrated into allocation, such that when you call malloc for example, you sweep until you find a ...
2
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1answer
811 views
What is the time complexity of memory allocation assumed to be?
It is well-known that dynamic arrays have an amortized $O(1)$ time complexity for adding one item, but a worst-case $O(n)$ complexity. This is because for particular values of $n$, there is no more ...
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2answers
41 views
If you increase the address space for an OS, does the Phys Mem used by the program increase?
I am learning about the OS.
I know: that Address Space Size = # of pages x page size
So if I increase Address Space Size, then the number of pages increases:(not the page size). However, isn't the ...
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1answer
1k views
Why do we use dynamic memory allocation in general and why did we use it in this particular example? [closed]
Dynamic Programming C/C++ implementation of LIS(Longest Increasing Subsequence) problem
...
41
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8answers
11k views
How are variables stored in and retrieved from the program stack?
Apologies in advance for the naivety of this question. I am a 50 year old artist trying to properly understand computers really for the first time. So here goes.
I have been trying to understand how ...
1
vote
1answer
840 views
How does malloc(sizeof(char)) work [closed]
AFAIK, malloc(sizeof(char)) is intended to allocate a 1-byte block of VM and strcpy requires that
the destination string dest must be large enough to receive the copy
That means theorically that ...
2
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1answer
457 views
Do modern operating systems use memory control blocks?
I was taught in my operating systems class that sections of memory in the heap are marked as free/occupied through the use of memory control blocks (MCB). The generalized definition of an MCB that was ...
2
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2answers
3k views
Row Major Vs Column Major
People prefer accessing a 2D array in row-major order than column-major order. Why row-major is efficient? Is there some advantage of row major as compare to column major wrt memory.
0
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1answer
99 views
Less used data (1 byte) in memory address holding 4 bytes [closed]
I need to store two distinct variables of 1 byte size in memory.
My memory system stores 4 bytes at one address; therefore, you cannot address byte 3 directly, and you have to logically access it ...
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0answers
165 views
Direct Mapped Cache, textbook excerpt clarification, identifying block field
I have an excerpt from my textbook concerning direct mapped cache that I would like further clarification on, the text reads.....
"Consider the following example: Assume memory consists of 2^14 ...
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1answer
6k views
How to compute total internal and external fragmentation
I want to find the total external and internal fragmentation. What I understand is that external fragmentation occurs when processes are loaded and removed from memory, causing memory to be broken ...
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3answers
846 views
Does word addressable memory have more bytes than byte addressable memory?
Well, my question - if word addressable memory has more bytes than byte addressable memory - is derived from the fact that in word addressable memory each address addresses a word and in byte ...
2
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1answer
50 views
Why not space out memory allocations?
In ext4 file system, the files are spaced out as far apart as reasonably possible to allow for efficient reallocation. Why do we not do this in memory?
Why not allocate one memory as page 20, and the ...
3
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1answer
345 views
Combining adjacent memory blocks
This is a conceptual issue that I am having in designing an algorithm for a memory allocator that works in conjunction with memory pooling. Free blocks are put on one of several free lists within the ...
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2answers
1k views
Why is data fragmentation not possible on main memory (RAM)?
I am wondering why data fragmentation is a problem on main memory.
On a software level, virtual addresses are used anyway. So why can one address space not be split up into multiple segments, like a ...
0
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1answer
64 views
Memory address of variable after reassignment
When a local variable is reassigned a different value/object, does its position/address change in the stack?
6
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1answer
510 views
How do arrays work “under the hood”?
In some languages (such as C), arrays seem very simple to me. When allocating memory for these, all you need to do is pick a starting point in memory and then allocate the next ...
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2answers
7k views
Can someone explain this diagram about Slab Allocation?
I'm trying to understand how Slab Allocation works and why it is different or better than ordinary paging.
I found this diagram which I believe would be helpful if it had more explanation.
Some ...
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1answer
6k views
Would it be possible to use the cloud for RAM?
I'm not sure if this is the right place to ask but I had this idea. Since the cloud can be used for storing memory, would it be possible to use it for RAM too?
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0answers
289 views
When there's no memory, should malloc or read/write fail?
To my surprise, I recently found out that Windows would fail a large memory allocation even if little of said memory is to actually be used, e.g. even if you don't want the swap, you better not ...
2
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2answers
547 views
where is all deleted data will go from memory system/internet? [closed]
where is all deleted data will go from a memory system ?
if it is not deleting actually where it storing ?
i am always wonder about this when we are sending something to a memory system it takes ...
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3answers
13k views
How are hash table's values stored physically in memory?
Question:
How are hash table's values stored in memory such that space if efficiently used and values don't have to be relocated often?
My current understanding (could be wrong):
Let's say I have 3 ...
0
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1answer
68 views
In Ada95 how many bytes does integer occupied in memory? [closed]
Also asking for float, character, ect.
0
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1answer
53 views
Name for almost random memory distribution on the heap
If I had a heap like the following: with blue blocks being occupied memory and white blocks being free memory
What is the general name given to the situation illustrated, where the free and occupied ...
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3answers
3k views
How is heap memory allocated to a process?
I want to better understand how OS provides heap memory to a process. Here by heap memory I mean the memory allocated dynamically, say by call to malloc.
When a ...
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1answer
126 views
In case of program overlays; is it necessary to have error handling routine in memory, regardless of error?
I came accross the question regarding program overlays,
...
0
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1answer
5k views
Dynamic loading vs. dynamic linking?
What is the difference between dynamic loading and dynamic linking?
Both systems seem to allow shared libraries, but I am struggling to differentiate between them.
0
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1answer
108 views
How Does Dynamic Heap Storage Have Something to Do with Heap?
There are three typical ways to allocate memory for programs: static, stack and dynamic heap. However, when I look at the implementation of dynamic heap memory allocation from wikipedia , what I found ...
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2answers
9k views
Direct vs. Random Access
Would someone please clarify for me the difference between direct and random access?
Specifically, why does this Wikipedia article on Direct Access Storage Devices distinguish between the two:
...
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3answers
4k views
How does worst-fit memory allocation react when encountering contiguous empty memory blocks?
So I have a problem understanding how the worst-fit protocol for memory allocation reacts to contiguous blocks of empty memory. None of the examples I have found address this possibility.
For ...
11
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1answer
4k views
Swap space management during pure demand paging
The following is a doubt that I came across while doing a OS home assignment - however, it seems more concept-based than a straightforward coding question, so IMHO I don't think the homework tag is ...
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3answers
1k views
Clever memory management with constant time operations?
Let's consider a memory segment (whose size can grow or shrink, like a file, when needed) on which you can perform two basic memory allocation operations involving fixed size blocks:
allocation of ...
