Is it possible to create an integer of any size with dynamic memory?

Question

Is it possible to use dynamic memory allocation, or some other method, to make a 1000-bit (or 1024-bit) integer variable?

Obviously, this is an insane amount, but I'm just using this amount as an example. Basically, can I make an integer any size I want? I'm thinking maybe dynamic memory allocation would work, or perhaps something to do with char arrays?

No. The CPU can only do arithmetic on its native integer sizes. — Paul Ogilvie, Jul 03 '21 at 13:09
You can allocate any amount of memory and call it an "integer" but you have to do the manipulation and arithmetic yourself. — Paul Ogilvie, Jul 03 '21 at 13:10
Not quite any size, just as much as the system will give you. That may be larger than physical memory; the operating system can use swap space to provide additional memory, but there is some limit. — Eric Postpischil, Jul 03 '21 at 13:24

Mureinik · Accepted Answer · 2021-07-03T13:15:50.273

3

Depends on what exactly you mean.
If you mean "a fully functional int that the compiler knows how to handle and can be used with the built-in arithmetic operators", the answer would be no.
If you mean "allocate an arbitrary size of memory that I'll treat as a continuous integer and write my own custom mathematical functions for", the answer is most definitely yes, and there are in fact several libraries that do exactly that.

edited Jul 03 '21 at 13:15

answered Jul 03 '21 at 13:12

Mureinik

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Perfect! My reasoning for this is a mix of curiosity and practical applications (i.e. writing a code to find giant prime numbers). I'm mostly curious as to how computer are able to store and process numbers with millions of digits. – Victor Resnov Jul 03 '21 at 13:15

score 2 · Answer 2 · answered Jul 03 '21 at 13:11

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Yes. For example the GNU Multiple Precision Arithmetic Library (GMP) does this.

answered Jul 03 '21 at 13:11

orlp

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Is it possible to create an integer of any size with dynamic memory?

2 Answers2