| Routines

2D8E: THE 'INT-STORE' SUBROUTINE

Used by the routines at multiply, truncate, negate and sgn. This subroutine stores a small integer n (-65535<=n<=65535) in the location addressed by HL and the four following locations, i.e. n replaces the first (or second) number at the top of the calculator stack. The subroutine returns HL pointing to the first byte of n on the stack.
Input
C | Sign byte
DE | Value to store
HL | Address of the first byte of the slot on the calculator stack
INT_STORE | 2D8E | PUSH HL | The pointer to the first location is saved.
| 2D8F | LD (HL),$00 | The first byte is set to zero.
| 2D91 | INC HL | Point to the second location.
| 2D92 | LD (HL),C | Enter the second byte.
The same mechanism is now used as in INT_FETCH to two's complement negative numbers. This is needed e.g. before and after the multiplication of small integers. Addition is however performed without any further two's complementing before or afterwards.
| 2D93 | INC HL | Point to the third location.
| 2D94 | LD A,E | Collect the less significant byte.
| 2D95 | XOR C | Two's complement it if the number is negative.
| 2D96 | SUB C
| 2D97 | LD (HL),A | Store the byte.
| 2D98 | INC HL | Point to the fourth location.
| 2D99 | LD A,D | Collect the more significant byte.
| 2D9A | ADC A,C | Two's complement it if the number is negative.
| 2D9B | XOR C
| 2D9C | LD (HL),A | Store the byte.
| 2D9D | INC HL | Point to the fifth location.
| 2D9E | LD (HL),$00 | The fifth byte is set to zero.
| 2DA0 | POP HL | Return with HL pointing to the first byte of n on the stack.
| 2DA1 | RET