You might have heard about 16-bit computers, 32-bit computers, 64-bit computers, etc. They refer to memory word length (total number of bits per memory word) of a computer. Word length of small computers is 8, 16, or 32 bits, whereas that of large computers is 64 bits or more. The obvious question that aries is- "What is the advantage of having more number of bits per word, instead of having more words of smaller size (length)?
For an answer to this question, imagine a highway with eight lanes and heavy flow of traffic. If we expand it to sixteen lanes, traffic flow speeds up considerably. "8 bits" is analogous to number of "lanes" on a microchip, More bits mean a more rapid flow of electronic signals, in other words, a faster computer. Hence, the amount of data that an 8-bit computer can transfer to and from memory in one minute, a 32-bit computer may transfer in a few seconds.
Data and instructions move to and from memory as one or more at a time. Therefore, even if the electronic circuits used are comparable in speed, computers having smaller word length will be slower in operation than computers having larger word length. This difference is analogous to providing the user of a computer having smaller word length with a small data shovel and the user of a computer having larger word length with a large data shovel. Even though they both be shoveling at comparable speeds, the user with smaller shovel will be slower because he/ she needs more shovelfuls to move the same amount of data..