D is the symbol in differential of higher mathematics, dq represents the minimum change of electric quantity, and dt represents the extremely short time. Dq/dt, which represents the ratio of the minimum change of electric quantity to the extremely short time used. (It is equivalent to the rate of change of electricity, and the acceleration learned before is expressed by the rate of change of speed, that is, A = DV/DT, and this d is not a quantity and cannot be omitted).

D stands for decimal, H stands for hexadecimal, B stands for binary and OQ stands for octal.

Extended data:

Generally speaking, numbers come from the accumulation and calculation of objects, and natural numbers are produced one after another. Today, the most commonly used counting method in the world is decimal, which has become an indispensable part of people's lives.

Decimalization was invented by ancient Indians. From 2500 BC to 65438 BC+0750 BC, the ancient Indians adopted the decimal counting method. First, they invented the nine number symbols 1-9 and the positioning counting method, and then put forward the theory of zero-sum decimal as the basic point of calculus.

The reason why Indians follow the rule of "one in ten" is probably because they use 10 fingers to assist in counting. When decimal system is adopted, the odd number of counting is only 0, 1, 2, 3...9. Many ethnic groups in Central Asia are gradually adopting this simple counting method.