Menu
We have 8-bit, 16-bit, 32-bit and 64-bit hardware architectures and operating systems. But not, say, 42-bit or 69-bit ones.
Why? Is it something fundamental that makes 2^n bits a better choice, or is just about compatibility with existing systems? (It's obviously convenient that a 64-bit register can hold two 32-bit pointers, or that a 32-bit data unit can hold 4 bytes.)
354
Because two is the base of the binary numeral system, powers of two are common in computer science. Written in binary, a power of two always has the form 100...000 or 0.00... 001, just like a power of 10 in the decimal system.
Base 2 prefixes make sense for memory capacity because memory chips have a power-of-two capacity. Base 2 prefixes makes sense for address space because n bits can identify 2^n different addresses.
You can't store anything other than a 1 or a 0 in a bit, so you can store 2 different numbers in a bit (but not at the same time).
That's mostly a matter of tradition. It is not even always true. For example, floating-point units in processors (even contemporary ones) have 80-bits registers. And there's nothing that would force us to have 8-bit bytes instead of 13-bit bytes.
Sometimes this has mathematical reasoning. For example, if you decide to have an N bits byte and want to do integer multiplication you need exactly 2N bits to store the results. Then you also want to add/subtract/multiply those 2N-bits integers and now you need 2N-bits general-purpose registers for storing the addition/subtraction results and 4N-bits registers for storing the multiplication results.
59
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
