All Arithmetic is 32-bits

MIPS has no instructions for byte arithmetic nor for halfword arithmetic. For a single operation (such as above), the results in the low-order bytes are the same. The carry out of the high-order bit (of the byte or halfword) is part of the 32-bit result. Further operations may increasingly involve high-order bits. The result after several operations will be a correct result, but may not fit into the original size of the operands.