HLASM: V1R6 Language Ref

Syntax of binary, decimal, and hexadecimal floating-point constants|||||type extensionthe type of conversion required to assemble the constant. Valid values are:null Hexadecimal floating-point constant which is converted using theconversion logic of rounding mode 1 and slightly less precisealgorithmsB Binary floating-point constant which is converted allowing allrounding modesD Decimal floating-point constant which is converted allowing allrounding modesH Hexadecimal floating-point constant which is converted allowing allrounding modesprogram_typeassign a programmer determined 32-bit value to the symbol naming the DCinstruction, if a symbol was present.modifierdescribes the length, the scaling and the exponent of the nominal_value. Theminimum length of the 'H' hexadecimal constant is 12 bits. The minimumlength in bits of the binary constant is:9 Short floating-point constant12 Long floating-point constant16 Extended floating-point constantThis minimum length allows for the sign, exponent, the implied unit bit whichis considered to be one for normalized numbers and zero for zeros anddenormalized numbers.The exponent modifier can be in the range from −2 31 to 2 31 −1 if either B or H isspecified as a type extension. The only valid length modifiers for decimalfloating point constants are 4 bytes (short format), 8 bytes (long format), and16 bytes (extended format).nominal_valuedefines the value of the constant and can include the integer, fraction or mixednumber followed by an optional signed exponent and an optional explicitrounding mode.The assembler imposes no limits on the exponent values that may be specified.The BFP architecture limits the actual values that can be represented; awarning message is issued whenever a specified value can not be representedexactly.The rounding mode identifies the rounding required when defining afloating-point constant. The valid values are those displayed in Figure 18 onpage 160.Note: As binary floating-point does not support scaling, the scale modifier isignored and a warning message issued if the scaling modifier is specifiedwhen defining a binary floating-point constant. The H type extension causesHLASM to use a different conversion algorithm for hexadecimalfloating-point data. The results are correctly rounded for all values. Withoutthe H type extension, some rare values could be in error by 1 unit in the lastplace (ulp).168 HLASM: V1R6 Language Ref