Byte addressing 8 bits; in fact, depending on the platform, byte sizes of 1 to 48 bits have been used in the past. Therefore, the term "octet" is used where the context makes byte-length ambiguous. For example, in the 1980s, Honeywell mainframes had 36-bit words, and were byte-addressable in 9-bit bytes, or "nonets", They used 7- or 8-bit character codes, either of which were stored one to each 9-bit byte, making characters individually addressable. To illustrate why byte addressing is useful, consider the IBM 7094, which is word-addressable and has no concept of a byte. It has 36-bit words, and stores its
Byte addressing be achieved in one instruction: store this character code at that byte address. Text programs are easier to write, smaller, and run faster. The advantage of word addressing is that more memory can be addressed in the same number of bits. The IBM 7094 has 15-bit addresses, so could address 32,768 words of 36 bits. The machines were often built with a full complement of addressable memory. Addressing 32,768 bytes of 6 bits would have been much less useful for scientific and engineering users. Or consider the 32-bit Pentium processor. Its 32-bit address bus can address 4 billion different items.