| Routines

08967: THE 'STK-TO-BC' SUBROUTINE

Used by the routines at PR_ITEM_1, POINT_SUB, PLOT, DRAW_LINE, S_SCRN_S and S_ATTR_S. This subroutine loads two floating point numbers into the BC register pair. It is thus used to pick up parameters in the range 0 to 255. It also obtains in DE the 'diagonal move' values (+/-1,+/-1) which are used in DRAW_LINE.
Output
B | First number from the calculator stack
C | Second number from the calculator stack
D | Sign of the first number (1 or 255)
E | Sign of the second number (1 or 255)
STK_TO_BC | 08967 | CALL STK_TO_A | First number to A.
| 08970 | LD B,A | Hence to B.
| 08971 | PUSH BC | Save it briefly.
| 08972 | CALL STK_TO_A | Second number to A.
| 08975 | LD E,C | Its sign indicator to E.
| 08976 | POP BC | Restore first number.
| 08977 | LD D,C | Its sign indicator to D.
| 08978 | LD C,A | Second number to C.
| 08979 | RET | BC, DE are now as required.