M423: Increment a Byte of a Packed Vector

Author(s): J. Zoll, P. Rastl	Library: KERNLIB
Submitter:	Submitted: 28.01.1971
Language: Fortran or Assembler	Revised: 16.09.1991

INCBYT allows incrementing a specified byte of a packed byte vector (cf. PACBYT (M422)).

Structure:

FUNCTION subprogram
User Entry Names: INCBYT

Usage:

    LOST = INCBYT(INC,MX,JX,MPACK)

The 3-word vector MPACK specifies the packing parameters (much like for PACBYT (M422), but is not allowed):

MPACK(1)

, number of bits per byte.

MPACK(2)

, number of bytes per word.

MPACK(3)

, the maximum capacity of any byte, 2**NBITS-1.

INCBYT adds the increment INC into the JX'th byte of the packed byte-vector MX and returns any byte overflow, i.e. the part of INC which cannot be added into the byte, because it now contains MPACK(3).