Software and hardware engineers who have to deal with byte and bit order issues know the process is like walking a maze. Though we usually come out of it, we consume a handful of our brain cells each time. This article tries to summarize the various areas in which the business of byte and bit order plays a role, including CPU, buses, devices and networking protocols. We dive into the details and hope to provide a good reference on this topic. The article also tries to suggest some guidelines and rules of thumb developed from practice. We probably are familiar with the word endianness. First introduced by Danny Cohen in 1980, it describes the method a computer system uses to represent multi-byte integers. Big endian refers to the method that stores the most significant byte of an integer at the lowest byte address. Little endian is the opposite; it refers to the method of storing the most significant byte of an integer at the highest byte address. Bit order usually follows the same endianness as the byte order for a given computer system. That is, in a big endian system the most significant bit is stored at the lowest bit address; in a little endian system, the least significant bit is stored at the lowest bit address.

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