| Routines

11662: 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 | 11662 | PUSH HL | The pointer to the first location is saved.
| 11663 | LD (HL),0 | The first byte is set to zero.
| 11665 | INC HL | Point to the second location.
| 11666 | 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.
| 11667 | INC HL | Point to the third location.
| 11668 | LD A,E | Collect the less significant byte.
| 11669 | XOR C | Two's complement it if the number is negative.
| 11670 | SUB C
| 11671 | LD (HL),A | Store the byte.
| 11672 | INC HL | Point to the fourth location.
| 11673 | LD A,D | Collect the more significant byte.
| 11674 | ADC A,C | Two's complement it if the number is negative.
| 11675 | XOR C
| 11676 | LD (HL),A | Store the byte.
| 11677 | INC HL | Point to the fifth location.
| 11678 | LD (HL),0 | The fifth byte is set to zero.
| 11680 | POP HL | Return with HL pointing to the first byte of n on the stack.
| 11681 | RET