Differences

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--- base:kernal_floating_point_mathematics [2019-10-14 09:44] – ARISGN / STRNG1 description augmented silverdr
+++ base:kernal_floating_point_mathematics [2019-10-14 09:45] – [Zero Page Locations] silverdr
@@ Line 41: / Line 41: @@
 **$68** is used during normalisation, and also when converting a FP number to an integer (two similar operations).
-**$6f** holds the sign result of arithmetic operations. This byte is set when FAC2 is loaded, not when FAC1 is loaded. FAC2 should be loaded after FAC1 before addition, or multiplication. Subtraction negates FAC1 and then compares, setting this byte. Unless called at FDIVT ($bb12). division does its own compare, so copying FAC1 into FAC2 and then loading FAC1 does not produce erroneous signs. When FDIVT is used, value of this byte may contain incorrect sign, leading to errors in later operations. Please note that this address is used also by other routines – as string pointer for example – and therefore should be treated as volatile, even if no FP routines are invoked after its value is established.
+**$6f** holds the sign result of arithmetic operations. This byte is set when FAC2 is loaded, not when FAC1 is loaded. FAC2 should be loaded after FAC1 before addition, or multiplication. Subtraction negates FAC1 and then compares, setting this byte. Unless called at FDIVT ($bb12), division does its own compare, so copying FAC1 into FAC2 and then loading FAC1 does not produce erroneous signs. When FDIVT is used, value of this byte may contain incorrect sign, leading to errors in later operations. Please note that this address is used also by other routines – as string pointer for example – and therefore should be treated as volatile, even if no FP routines are invoked after its value is established.
 **$70** is the low order rounding byte for FAC1, essentially an extension of the mantissa. It is cleared whenever a variable is loaded into FAC1. Storing 0 here after obtaining a result can speed execution (at the cost of accuracy) by avoiding the rounding routines.