Q:

Why would a word be bigger than 1 byte?

If a variable is a boolean or a char (in C/C++) or a byte (in some language like Java - no wait Java's on a VM) and the CPU uses words larger than 1 byte, isn't space wasted? I heard when the variable is stored in memory it can be stored more compact for example 1 byte even though a word is 4 bytes. Can someone explain how this happens? It seems backwards because registers are more at a premium than RAM.

A:

In spite of their ability to store numbers, registers are not exactly "space".
Consider this example: you have a bunch of business cards in a big box, and you would like to arrange them alphabetically. In the process of doing so, you move cards in the box from one place to the other. Although you hold a card in your hands while you move it to its new place in the box, your hands do not provide storage for the cards in the same sense that the box does. The place in your hands is too valuable to be called "space".
Continuing with the cards analogy, imagine that cards have different sizes. The size of your hand lets you hold one large card, two medium cards, or four tiny cards at a time. However, when you sort the cards, the ability to take multiple cards is rarely of advantage to you, especially when the cards are uniformly shuffled: multiple cards have multiple destination spots, so you would need to do more complex or unnecessary operations if you grab multiple cards at the same time.
Similarly, a register of a CPU may contain multiple bytes, but if you need to perform a computation, there is often no way to tell CPU which bytes to use: a register participates in an operation as an indivisible unit. That is why an entire word is used for the data in the register, even though only a single byte would be sufficient.

A:

Generally speaking a word is the amount of data that fits in a single register.  
If you made register's narrower, like say, 8 bits, than it would take multiple cycles to add 2 32-bit ints.  
I also think that you want your RAM address space to fit inside a word too.

