The operation method of disease classification coding can basically be divided into four steps:

(1) First of all, we must determine the guiding words, which are equivalent to the guiding words used in library retrieval.

(2) After determining the leading word, look for the code in the letter index (Volume III).

(3) Check whether the code in the category table (Volume I) is correct.

(4) The coding operation of tumor requires two codes, so it needs to be re-operated.