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What is meant by a 32 bit processor, or generally an n-bit processor?

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Whilst you will probably get a good answer below, I would recommend reading Wikipedia - en.wikipedia.org/wiki/32-bit –  William Hilsum Sep 23 '10 at 2:39
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I think understanding how a processor works, in general, will naturally explain what the 32 means. Essentially it's the size of the registers on the chip itself –  Joe Philllips Sep 23 '10 at 3:57
    
A bit is unit of storage in computer.data stored in computer in cpu in registers. stroing capacity of register expressed interms of "bits". only two types of bit is possible(0 & 1). ex: 16-bit register stored only 16-bit size data. and also processing also with 16-bit data only. –  user117334 Feb 8 '12 at 5:32
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3 Answers

up vote 10 down vote accepted

The simplest explanation is that a 32bit processor can work with numbers from 0 through to 2^32 (4,294,967,295). This means it can address only that many bytes of system memory (just short of 4GB's), and only do calculations on numbers where the answer is less then that.

a 64bit processor can work with numbers from 0 through to 2^64 (18,446,744,073,709,551,615), giving it a much higher address space.

To continue to your n-bit question: It will simply be able to work with numbers on 2^n.

Wikepedia has a good series of articles about bit width and the maths behind it all.

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The 'working with numbers up to 2^n' is misleading. The 32bit Pentium can generate 64bit results, e.g. mul ebx calculates eax*ebx and stores the 64bit result in edx:eax. Generally, it's the size of a register, but even this has been misleading in the past. –  Skizz Sep 23 '10 at 8:30
    
This is a slightly misleading answer. The address, data, and internal buses do not have to match in size. For example, the 16-bit 286 processor had a 24-bit address bus. The 16-bit 8088 processor (due to internal primary data size) had an 8-bit data bus and a 20-bit address bus (and could generate 32-bit results for very specific operations). :-) –  Brian Knoblauch Sep 23 '10 at 14:16
    
well you guys are getting geeky about the issue. the answer is not wrong conceptually; only technically. But give the obvious low know-how of the user ; i think its a fair answer –  Ritwik G May 4 '11 at 10:53
    
Specific to Intel/AMD 64-bit CPUs - they also feature more general purpose registers - this also helps performance as it can prevent the CPU from accessing slower RAM more. However more registers is not necessarily a function of CPU "bitness." –  ultrasawblade Mar 31 '12 at 14:36
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A Bit is the smallest unit of information storage in a computer processor. Just like a switch can be either off or on, the bit can also have either one of two states often denoted 0 and 1.
The processor/CPU itself is composed primarily of a dozen or so buckets of these bits which are called Registers. So registers are buckets of bits that can hold data in a processor. Some of these are general purpose registers (originally name A,B,C...) and others are special purpose (with more funky names). There are other parts of modern processors for other functionalities like basic arithmatic by arithmetic logic unit (ALU) etc etc.

Earlier processors had registers with smaller number of bits like 8-bit and 16-bit etc. Currently we have processors with register sizes of 32 and 64 bit.

So a 32-bit processor has information storage buckets called registers each of which is 32-bit long. And their naming style have also evolved with their sizes from AX, BX, CX for the 16-bit types ....to now a days to EAX, EBX, ECX etc for the 32 bit registers. The special purpose registers in a 32-bit processor are also 32-bit long but they have horrible names that I am trying hard to forget:)

Enough theory .... Now lets see a snapshot of a modern 32-bit processor's some general purpose registers to get an idea of the relation of registers and bits:

alt text

Following is another snapshot of the processor, this time taken from a slightly higher altitude:

alt text

Finally a 10,000 feet altitude view of the processor in the overall scheme of computers data holding components.

alt text

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well, answer some questions then to get points! =) –  lajuette Sep 23 '10 at 9:22
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This answer should already seems to bring you enough points. You can edit the answer now to included the images. –  Suma Sep 23 '10 at 10:25
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8, 16, 32, 64... bit computing basically talks about how much information can be "passed around".

A bit is the basic information. 1 or 0. An 8 bit machine can process a chunk of information that is 8-bits wide. 16 bit machine can handle a bit that is 16 wide, basically doing 2 instructions for each cycle when compared to the 8 bit machine.

32, 64 bit computing refers to CPUs that work with data in those sizes, allowing more data to be passed per "cpu cycle". All other things being equal, it's easy to see how more = better/faster.

PCMag definition of 16 bit computing
PCMag Bit Specifications

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