为清楚理解和准确使用手册各部分的信息，定义必要的符号、缩写和术语。
A Define symbols, abbreviations and terminology necessary for the clear understanding and precise use of the information presented in various sections of the Handbook.
B In order to understand and use the information in the manual clearly, give the definition to the symbols, abbreviations and terms which are necessary.
C For clear understanding and accurate information about the use of each part of the manual define the necessary symbols, abbreviations and terms.