Here is what Keil C51 suggests:

I wrote the routine first in C51 as:

unsigned int num;

void main(void)
{
    num = num + 1;

    num = num - 1;
}

Here is the resulting assembly language as seen in the Keil simulator.....

7:         num = num + 1;
8 :
C:0x0003    0509     INC      0x09
C:0x0005    E509     MOV      A,0x09
C:0x0007    7002     JNZ      C:000B
C:0x0009    0508     INC      num(0x08)
9:         num = num - 1;
C:0x000B    1509     DEC      0x09
C:0x000D    7002     JNZ      C:0011
C:0x000F    1508     DEC      num(0x08)
10: }
C:0x0011    22       RET

So translating this back into "source code" of your format it could look like...

Inc16:
    INC  LOW
    MOV  A, LOW
    JNZ  L1
    INC  HIGH
L1: (...)


Dec16:
    DEC  LOW
    JNZ  L2
    DEC  HIGH
L2: (...)

Michael Karas