I understand the shape of the bytes behind a PACKED-DECIMAL number when on a Big-Endian machine. What I have not been able to discover is what shape would those bytes take on a Little-Endian machine.
Note: The reason I believe there does exist a separate format for such is because the IBM MQ Encoding field has the following values:-
MQENC_DECIMAL_NORMALMQENC_DECIMAL_REVERSEDOf MQENC_DECIMAL_REVERSED it simply says:-
Packed-decimal integers are represented in the same way as
MQENC_DECIMAL_NORMAL, but with the bytes arranged in reverse order. The bits within each byte are arranged in the same way asMQENC_DECIMAL_NORMAL.
Can anyone corroborate or refute this description?
For example, the number +123.45 stored in a PIC 9(3)V99 COMP-3 would have the following bytes:-
12 34 5C
The above quote suggests to me that if in reversed, the same packed decimal number would be represented on a Little-Endian machine as:-
5C 34 12
N.B. I have not tagged this question with ibm-mq, as I don't really think the crux of my question has anything to do with IBM MQ. It is simply the reason I am asking.
It looks like packed data is stored in "normal" byte order.
The following program was compiled with OpenCOBOL 1.1.0 on Ubuntu 16.04 on a Lenovo ThinkPad...
ID Division.
Program-ID. testcmp3.
Environment Division.
Input-Output Section.
File-Control.
Select OUTPUT01 Assign To './output01'
Status OUTPUT01-STATUS.
Data Division.
File Section.
FD OUTPUT01
Record 16
Block 0
Recording F.
01 OUTPUT01-REC PIC X(016).
Working-Storage Section.
01 CONSTANTS.
05 MYNAME PIC X(008) VALUE 'testcmp3'.
01 WS-OUTPUT01-REC.
05 WS-OUT-S94COMP PIC S9(004) COMP VALUE +0.
05 FILLER PIC X(001) VALUE HIGH-VALUES.
05 WS-OUT-S95COMP3 PIC S9(005) COMP-3 VALUE +0.
05 FILLER PIC X(008) VALUE SPACES.
01 WORK-AREAS.
05 OUTPUT01-STATUS PIC X(002) VALUE ZEROES.
Procedure Division.
OPEN OUTPUT OUTPUT01
IF OUTPUT01-STATUS NOT = '00'
DISPLAY
MYNAME
' open of OUTPUT01 status = '
OUTPUT01-STATUS
END-IF
PERFORM 100-WRITE 100 TIMES
CLOSE OUTPUT01
STOP RUN.
100-WRITE.
WRITE OUTPUT01-REC FROM WS-OUTPUT01-REC
ADD 1 TO WS-OUT-S94COMP
ADD 1 TO WS-OUT-S95COMP3
.
...with the option binary-byteorder set to native.
The resulting file, displayed with the hexdump program, follows.
00000000 00 00 ff 00 00 0c 20 20 20 20 20 20 20 20 20 20 |...... |
00000010 01 00 ff 00 00 1c 20 20 20 20 20 20 20 20 20 20 |...... |
00000020 02 00 ff 00 00 2c 20 20 20 20 20 20 20 20 20 20 |....., |
00000030 03 00 ff 00 00 3c 20 20 20 20 20 20 20 20 20 20 |.....< |
00000040 04 00 ff 00 00 4c 20 20 20 20 20 20 20 20 20 20 |.....L |
00000050 05 00 ff 00 00 5c 20 20 20 20 20 20 20 20 20 20 |.....\ |
00000060 06 00 ff 00 00 6c 20 20 20 20 20 20 20 20 20 20 |.....l |
00000070 07 00 ff 00 00 7c 20 20 20 20 20 20 20 20 20 20 |.....| |
00000080 08 00 ff 00 00 8c 20 20 20 20 20 20 20 20 20 20 |...... |
00000090 09 00 ff 00 00 9c 20 20 20 20 20 20 20 20 20 20 |...... |
000000a0 0a 00 ff 00 01 0c 20 20 20 20 20 20 20 20 20 20 |...... |
000000b0 0b 00 ff 00 01 1c 20 20 20 20 20 20 20 20 20 20 |...... |
000000c0 0c 00 ff 00 01 2c 20 20 20 20 20 20 20 20 20 20 |....., |
000000d0 0d 00 ff 00 01 3c 20 20 20 20 20 20 20 20 20 20 |.....< |
000000e0 0e 00 ff 00 01 4c 20 20 20 20 20 20 20 20 20 20 |.....L |
000000f0 0f 00 ff 00 01 5c 20 20 20 20 20 20 20 20 20 20 |.....\ |
00000100 10 00 ff 00 01 6c 20 20 20 20 20 20 20 20 20 20 |.....l |
00000110 11 00 ff 00 01 7c 20 20 20 20 20 20 20 20 20 20 |.....| |
00000120 12 00 ff 00 01 8c 20 20 20 20 20 20 20 20 20 20 |...... |
00000130 13 00 ff 00 01 9c 20 20 20 20 20 20 20 20 20 20 |...... |
00000140 14 00 ff 00 02 0c 20 20 20 20 20 20 20 20 20 20 |...... |
00000150 15 00 ff 00 02 1c 20 20 20 20 20 20 20 20 20 20 |...... |
00000160 16 00 ff 00 02 2c 20 20 20 20 20 20 20 20 20 20 |....., |
00000170 17 00 ff 00 02 3c 20 20 20 20 20 20 20 20 20 20 |.....< |
00000180 18 00 ff 00 02 4c 20 20 20 20 20 20 20 20 20 20 |.....L |
00000190 19 00 ff 00 02 5c 20 20 20 20 20 20 20 20 20 20 |.....\ |
000001a0 1a 00 ff 00 02 6c 20 20 20 20 20 20 20 20 20 20 |.....l |
000001b0 1b 00 ff 00 02 7c 20 20 20 20 20 20 20 20 20 20 |.....| |
000001c0 1c 00 ff 00 02 8c 20 20 20 20 20 20 20 20 20 20 |...... |
000001d0 1d 00 ff 00 02 9c 20 20 20 20 20 20 20 20 20 20 |...... |
000001e0 1e 00 ff 00 03 0c 20 20 20 20 20 20 20 20 20 20 |...... |
000001f0 1f 00 ff 00 03 1c 20 20 20 20 20 20 20 20 20 20 |...... |
00000200 20 00 ff 00 03 2c 20 20 20 20 20 20 20 20 20 20 | ...., |
00000210 21 00 ff 00 03 3c 20 20 20 20 20 20 20 20 20 20 |!....< |
00000220 22 00 ff 00 03 4c 20 20 20 20 20 20 20 20 20 20 |"....L |
00000230 23 00 ff 00 03 5c 20 20 20 20 20 20 20 20 20 20 |#....\ |
00000240 24 00 ff 00 03 6c 20 20 20 20 20 20 20 20 20 20 |$....l |
00000250 25 00 ff 00 03 7c 20 20 20 20 20 20 20 20 20 20 |%....| |
00000260 26 00 ff 00 03 8c 20 20 20 20 20 20 20 20 20 20 |&..... |
00000270 27 00 ff 00 03 9c 20 20 20 20 20 20 20 20 20 20 |'..... |
00000280 28 00 ff 00 04 0c 20 20 20 20 20 20 20 20 20 20 |(..... |
00000290 29 00 ff 00 04 1c 20 20 20 20 20 20 20 20 20 20 |)..... |
000002a0 2a 00 ff 00 04 2c 20 20 20 20 20 20 20 20 20 20 |*...., |
000002b0 2b 00 ff 00 04 3c 20 20 20 20 20 20 20 20 20 20 |+....< |
000002c0 2c 00 ff 00 04 4c 20 20 20 20 20 20 20 20 20 20 |,....L |
000002d0 2d 00 ff 00 04 5c 20 20 20 20 20 20 20 20 20 20 |-....\ |
000002e0 2e 00 ff 00 04 6c 20 20 20 20 20 20 20 20 20 20 |.....l |
000002f0 2f 00 ff 00 04 7c 20 20 20 20 20 20 20 20 20 20 |/....| |
00000300 30 00 ff 00 04 8c 20 20 20 20 20 20 20 20 20 20 |0..... |
00000310 31 00 ff 00 04 9c 20 20 20 20 20 20 20 20 20 20 |1..... |
00000320 32 00 ff 00 05 0c 20 20 20 20 20 20 20 20 20 20 |2..... |
00000330 33 00 ff 00 05 1c 20 20 20 20 20 20 20 20 20 20 |3..... |
00000340 34 00 ff 00 05 2c 20 20 20 20 20 20 20 20 20 20 |4...., |
00000350 35 00 ff 00 05 3c 20 20 20 20 20 20 20 20 20 20 |5....< |
00000360 36 00 ff 00 05 4c 20 20 20 20 20 20 20 20 20 20 |6....L |
00000370 37 00 ff 00 05 5c 20 20 20 20 20 20 20 20 20 20 |7....\ |
00000380 38 00 ff 00 05 6c 20 20 20 20 20 20 20 20 20 20 |8....l |
00000390 39 00 ff 00 05 7c 20 20 20 20 20 20 20 20 20 20 |9....| |
000003a0 3a 00 ff 00 05 8c 20 20 20 20 20 20 20 20 20 20 |:..... |
000003b0 3b 00 ff 00 05 9c 20 20 20 20 20 20 20 20 20 20 |;..... |
000003c0 3c 00 ff 00 06 0c 20 20 20 20 20 20 20 20 20 20 |<..... |
000003d0 3d 00 ff 00 06 1c 20 20 20 20 20 20 20 20 20 20 |=..... |
000003e0 3e 00 ff 00 06 2c 20 20 20 20 20 20 20 20 20 20 |>...., |
000003f0 3f 00 ff 00 06 3c 20 20 20 20 20 20 20 20 20 20 |?....< |
00000400 40 00 ff 00 06 4c 20 20 20 20 20 20 20 20 20 20 |@....L |
00000410 41 00 ff 00 06 5c 20 20 20 20 20 20 20 20 20 20 |A....\ |
00000420 42 00 ff 00 06 6c 20 20 20 20 20 20 20 20 20 20 |B....l |
00000430 43 00 ff 00 06 7c 20 20 20 20 20 20 20 20 20 20 |C....| |
00000440 44 00 ff 00 06 8c 20 20 20 20 20 20 20 20 20 20 |D..... |
00000450 45 00 ff 00 06 9c 20 20 20 20 20 20 20 20 20 20 |E..... |
00000460 46 00 ff 00 07 0c 20 20 20 20 20 20 20 20 20 20 |F..... |
00000470 47 00 ff 00 07 1c 20 20 20 20 20 20 20 20 20 20 |G..... |
00000480 48 00 ff 00 07 2c 20 20 20 20 20 20 20 20 20 20 |H...., |
00000490 49 00 ff 00 07 3c 20 20 20 20 20 20 20 20 20 20 |I....< |
000004a0 4a 00 ff 00 07 4c 20 20 20 20 20 20 20 20 20 20 |J....L |
000004b0 4b 00 ff 00 07 5c 20 20 20 20 20 20 20 20 20 20 |K....\ |
000004c0 4c 00 ff 00 07 6c 20 20 20 20 20 20 20 20 20 20 |L....l |
000004d0 4d 00 ff 00 07 7c 20 20 20 20 20 20 20 20 20 20 |M....| |
000004e0 4e 00 ff 00 07 8c 20 20 20 20 20 20 20 20 20 20 |N..... |
000004f0 4f 00 ff 00 07 9c 20 20 20 20 20 20 20 20 20 20 |O..... |
00000500 50 00 ff 00 08 0c 20 20 20 20 20 20 20 20 20 20 |P..... |
00000510 51 00 ff 00 08 1c 20 20 20 20 20 20 20 20 20 20 |Q..... |
00000520 52 00 ff 00 08 2c 20 20 20 20 20 20 20 20 20 20 |R...., |
00000530 53 00 ff 00 08 3c 20 20 20 20 20 20 20 20 20 20 |S....< |
00000540 54 00 ff 00 08 4c 20 20 20 20 20 20 20 20 20 20 |T....L |
00000550 55 00 ff 00 08 5c 20 20 20 20 20 20 20 20 20 20 |U....\ |
00000560 56 00 ff 00 08 6c 20 20 20 20 20 20 20 20 20 20 |V....l |
00000570 57 00 ff 00 08 7c 20 20 20 20 20 20 20 20 20 20 |W....| |
00000580 58 00 ff 00 08 8c 20 20 20 20 20 20 20 20 20 20 |X..... |
00000590 59 00 ff 00 08 9c 20 20 20 20 20 20 20 20 20 20 |Y..... |
000005a0 5a 00 ff 00 09 0c 20 20 20 20 20 20 20 20 20 20 |Z..... |
000005b0 5b 00 ff 00 09 1c 20 20 20 20 20 20 20 20 20 20 |[..... |
000005c0 5c 00 ff 00 09 2c 20 20 20 20 20 20 20 20 20 20 |\...., |
000005d0 5d 00 ff 00 09 3c 20 20 20 20 20 20 20 20 20 20 |]....< |
000005e0 5e 00 ff 00 09 4c 20 20 20 20 20 20 20 20 20 20 |^....L |
000005f0 5f 00 ff 00 09 5c 20 20 20 20 20 20 20 20 20 20 |_....\ |
00000600 60 00 ff 00 09 6c 20 20 20 20 20 20 20 20 20 20 |`....l |
00000610 61 00 ff 00 09 7c 20 20 20 20 20 20 20 20 20 20 |a....| |
00000620 62 00 ff 00 09 8c 20 20 20 20 20 20 20 20 20 20 |b..... |
00000630 63 00 ff 00 09 9c 20 20 20 20 20 20 20 20 20 20 |c..... |
00000640
The draft standard document ISO/IEC CD2.1 1989:202x says of the USAGE PACKED-DECIMAL phrase...
The USAGE PACKED-DECIMAL clause specifies that a radix of 10 is used to represent a numeric item in the storage of the computer. Furthermore, this clause specifies that each digit position shall occupy the minimum possible configuration in computer storage. Each implementor specifies the precise effect of the USAGE PACKED-DECIMAL clause upon the alignment and representation of the data item in the storage of the computer, including the representation of any algebraic sign. Sufficient computer storage shall be allocated by the implementor to contain the maximum range of values implied by the associated decimal picture character-string. If the WITH NO SIGN phrase is specified the representation of the data item in the storage of the computer reserves no storage for representing any sign value. The PICTURE character string of the data item shall not contain the symbol ‘S’; the data item is always considered to have a zero, or positive value.