User guide

170 CHAPTER 9. THE DESIGN OF CINTCODE
9.2.14 Corruption of B
To i mpr ove the efficiency of some hand writte n machine code interpreters, the following
instructions are permitted to corrupt the value held in B:
K KH KW Kn KnG KnG1 KnGH
SWL SWB MDIV CHGCO
All other instructions ei th er set B explicitly or l e ave its value unchanged.
9.2.15 Exceptions
When an exception occurs, the interpreter saves the Cintcode registers in its register
vector and yields the exception number as result. For exceptions caused by non existent
instructions, BRK, DIV or REM the program counter is left p oi nting to the offend-
ing instruction. For more details see the description of sys(Sys interpret,...) on
page 68.