Final answer:
In C++, when one bit is allocated for the sign of a number, the other bits are used to represent the value or magnitude of the number.
Step-by-step explanation:
In C++, when a data type reserves one bit for the sign of a number, indicating whether it's positive or negative, the rest of the bits are for representing the value of the number itself, which includes the magnitude without the sign. Specifically, the bits store the binary representation of the number's absolute value. In signed integer types, the sign bit (usually the most significant bit) determines the sign, with 0 typically representing positive and 1 for negative numbers, while the remaining bits are used as mentioned above to store the magnitude of the number.