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Maybe you can find your answer here https://www.quora.com/What-is-the-difference-between-32-bit-and-64-bit-operating-systems-In-this-context-what-does-bit-mean
computers used to have less --8 or 16 bit. the more bits, the more the computer can process. eight bits = one letter at a time. with 64 bit applications, they can't be run on computers that only have 32 bit OSs.
Jeremie is there any difference between data type's memory used in the application...
I am talking about 32 bit and 64 bit programming... not Operating system....
It is the no of bits that can be processed at an instant(called as a T state in microprocessors). In a 32bit processor, if we want to add two 32bit numbers, then the two numbers can be easily be added by the processor. But if we want to add two 64bit numbers in a 32bit processor, then the processor has to do multiple operations to get the job done(i.e. requires more T states). Simply speaking, more the number of bits of processor capacity, bigger the operations can be made fastly. As a high level programmer you don't need to bother much about these details, but knowing low level details will increase the ability to write programs efficiently.
The terms 32-bit and 64-bit refer to the way a computer's processor (also called a CPU), handles information. Processor calls data from Memory i.e. RAM by giving its address to MAR (Memory Address Register). Selector electronics then finds that address in the memory bank and retrieves the data and puts it in MDR (Memory Data Register) This data is recorded in one of the Registers in the Processor for further processing. Thats why size of Data Bus determines the size of Registers in Processor. Now, if my processor has 32 bit register, it can call data of 4 bytes size only, at a time. And if the data size exceeds 32 bits, then it would required two cycles of fetching to have the data in it. This slows down the speed of 32 bit Machine compared to 64 bit, which would complete the operation in ONE fetch cycle only. So, obviosly for the smaller data, it makes no difference if my processors are clocked at the same speed. Again, with 64 bit processor and 64 bit OS, my instructions will be of 64 bit size always... which unnecessarily uses up more memory space. http://net-informations.com/q/mis/x86.html