Final answer:
Two's complement is the encoding technique used to store negative numbers in a computer's memory.
Step-by-step explanation:
The encoding technique used to store negative numbers in a computer's memory is called two's complement. In two's complement, the most significant bit (leftmost bit) is used to represent the sign of the number. If the sign bit is 1, the number is negative, and if it is 0, the number is positive.
In two's complement, the remaining bits represent the magnitude of the number. To calculate the two's complement of a positive number, you invert all the bits and add one to the result. For example, to represent -5 using four bits, you start with the binary representation of 5, which is 0101. Inverting the bits gives 1010, and adding one gives the two's complement representation of -5 as 1011.
Unicode, ASCII, and floating-point notation are encoding techniques used for different purposes, but they are not specifically designed to store negative numbers.