The most significant bit (MSB) is the bit in a multiple-bit binary number with the largest value. This is usually the bit farthest to the left, or the bit transmitted first in a sequence. For example, in the binary number 1000, the MSB is 1, and in the binary number 0111, the MSB is 0.
The most significant byte, also abbreviated MSB, is the byte in a multiple-byte word with the largest value. As with bits, the MSB (byte) is normally the byte farthest to the left, or the byte transmitted first in a sequence.
When the MSB in a sequence is farthest to the left (or first), the least significant bit or byte (LSB) is usually the one farthest to the right (or last). In this case, the sequence is said to be big-endian . If the order is reversed so the MSB is farthest to the right (or last) and the LSB is farthest to the left (or first), the sequence is said to be little-endian .
Under certain circumstances, binary numbers or words may be neither little-endian nor big-endian. In encrypted data, for example, the bit or byte significance can be scrambled, in which case the MSB or LSB can appear anywhere in the sequence.