Tham khảo tài liệu 'the new c standard- p16', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Conditional inclusion 1883 The specification has changed between C90 and C99. The problem with any guideline recommendation is that the total cost is likely to be greater than the total benefit a cost is likely to be incurred in many cases and a benefit obtained in very few cases . For this reason 835 integer no recommendation is made here. The discussion on suffixed integer constants is also applicable in the constant type firet in l st context of a conditional inclusion directive. Example In the following the developer may assume that unwanted higher bits in the value of C will be truncated when shifted left. 1 define C OxllOOu 2 define INT_BITS 32 3 4 define TOP_BYTE C INT_BITS-8 5 6 if TOP_BYTE 0 7 . 8 endif 9 10 void f void 11 12 if TOP_BYTE 0 13 . 14 1881 This includes interpreting character constants which may involve converting escape sequences into execution if escape se-character set members. quences Commentary 133 trans a- This conversion also occurs in translation phase 5. tion phase 5 1882 Whether the numeric value for these character constants matches the value obtained when an identical character constant occurs in an expression other than within a if or elif directive is Commentary The C committee recognized that developers may choose to perform different phases of translation on different hosts. For instance source files may be preprocessed and then distributed for further translation on other different hosts. Common Implementations Differences between the numeric values in these two cases is rare although cases involving Ascii and EBCDIC character sets do occur . 3 EBCDIC Coding Guidelines Making use of the numeric value of character constants is making use of representation information which is representation incovered by a guideline recommendation. lowever there are cases where deviations may occur. formation Examle repWn- Example tation in- S ftt 141 formation see rootnote 141. using 1874 footnote .