定点数只能表示一定范围内的数（整数或小数，有符号或者无符号），浮点数虽将表示数的范围给予了较充分的扩宽，但仍只能表示（理论上）无限精度的数；本导论将引入一种新类型的数——效数，来完美地表示数的范围和精度两个方面，并简要介绍（演示）效数的四则运算。-Fixed-point can only say that within a certain range of numbers (integer or decimal, signed or unsigned), floating point, said although the number will be given a more full range of widening, but still can only say that (theoretically) infinite precision Number　this Introduction will introduce a new type of number- the number of effect, to perfectly express the number of range and accuracy of two aspects, and a brief descr iption (demo) effective number of four operations.