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alokagarwaljgd
New User
Joined: 02 Jun 2006
Posts: 28
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Hi,
1) Can any body tell me What is the exact difference between START and CSECT? I thought that they are same, but it seems that some difference does exists between them.
2) How to handle/achieve bit operations (e.g. TM) in COBOL?
Thanks,
Alok
Warning: Title edited |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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1) START/CSECT are Assembler Language terms. As I recall START designates the starting point of the pgm. CSECT means "control section" (I think) and designates a group of assembler instructions.
Maybe someone else will pitch in and fill in the details.
2) COBOL can use LE callable sevices (see link below). The bit manipulating routines are listed at the bottom of the link page.
You can also use COBOL code to manipulate bits. You can modify the code below to your own needs:
| Code: |
IDENTIFICATION DIVISION.
PROGRAM-ID. BITFLIPR.
AUTHOR. JACK.
ENVIRONMENT DIVISION.
******************************************************************
* CHANGES THE REQUESTED BIT OF THE BYTE PASSED BY THE CALLER. *
* THIS SUB PGM CAN BE CALLED FROM A PGM OR EXECUTED DIRECTLY *
* FROM JCL USING THE PARM FIELD IN THE EXEC CARD. THE JCL EX- *
* ECUTION IS INTENDED TO FACILITATE TESTING. *
* *
* WHEN INVOKED FROM A PGM, USE 1 OF THE FOLLOWING CALLING SEQ: *
* *
* CALL 'BITFLIPR' USING LK-PARM-LEN LK-PARM-DTA *
* CALL WS-PGMNAME USING LK-PARM-LEN LK-PARM-DTA *
* *
* WHERE, *
* *
* WS-PGMNAME CONTAINS THE 8 POSITION LITERAL 'BITFLIPR'. *
* LK-PARM-LEN IS AN 01 LEVEL DEFINED AS IN THE TABLE BELOW. *
* LK-PARM-DTA IS AN 01 LEVEL DEFINED AS FOLLOWS: *
* *
* 01 LK-PARM-DATA. *
* 05 LK-TGT-BYTE *
* 05 LK-BIT-NBR *
* 05 LK-ACTION *
* *
* WHERE THE 05 LEVELS ARE DEFINED AS IN THE TABLE BELOW. *
* *
* DESCRIPTION PICTURE COMMENTS *
* ************* ********** **************************
* PARM LENGTH S9(4) COMP CALLED FROM PGM THIS FLD *
* MUST HAVE VALUE OF -1. *
* CALLED FROM JCL THIS FLD *
* MUST BE OMMITTED. *
* TARGET BYTE X(1) THE BYTE THE CALLER *
* WANTS CHANGED. *
* BIT NUMBER 9(1) THE BIT THE CALLER *
* WANTS CHANGED. BIT NUM- *
* BERS RANGE FROM 1 TO 8 *
* FROM HI TO LOW ORDER. *
* ACTION X(1) THIS FLD HAS 1 OF 3 VAL- *
* UES: "1" - TURN BIT ON *
* "0" - TURN BIT OFF *
* "F" - FLIP THE BIT *
* *
* REMEMBER THAT THE TARGET BYTE IS UPDATED BY 'BITFLIPR'. *
* *
******************************************************************
CONFIGURATION SECTION.
DATA DIVISION.
FILE SECTION.
******************************************************************
WORKING-STORAGE SECTION.
******************************************************************
******************************************************************
01 WS-TABLES.
******************************************************************
******************************************************************
* *
* THIS TABLE IS USED TO DETERMINE THE VALUE THAT THE SUBJECT *
* BYTE MUST BE MULTIPLIED BY (MULT-VALUE) TO DETERMINE IF IT IS *
* CURRENTLY ON OR OFF (1 OR 0). *
* *
* THE TABLE IS ALSO USED TO DETERMINE THE INCREMENT/DECREMENT *
* REQUIRED TO TURN THE BIT ON OR OFF (ADD-SUB-VALUE). *
* *
******************************************************************
05 MULT-ADD-SUB-VALUES.
10 BIT1-MULT-VALUE PIC S9(004) VALUE +0 COMP.
10 BIT1-ADD-SUB-VALUE PIC S9(004) VALUE +128 COMP.
10 BIT2-MULT-VALUE PIC S9(004) VALUE +2 COMP.
10 BIT2-ADD-SUB-VALUE PIC S9(004) VALUE +64 COMP.
10 BIT3-MULT-VALUE PIC S9(004) VALUE +4 COMP.
10 BIT3-ADD-SUB-VALUE PIC S9(004) VALUE +32 COMP.
10 BIT4-MULT-VALUE PIC S9(004) VALUE +8 COMP.
10 BIT4-ADD-SUB-VALUE PIC S9(004) VALUE +16 COMP.
10 BIT5-MULT-VALUE PIC S9(004) VALUE +16 COMP.
10 BIT5-ADD-SUB-VALUE PIC S9(004) VALUE +8 COMP.
10 BIT6-MULT-VALUE PIC S9(004) VALUE +32 COMP.
10 BIT6-ADD-SUB-VALUE PIC S9(004) VALUE +4 COMP.
10 BIT7-MULT-VALUE PIC S9(004) VALUE +64 COMP.
10 BIT7-ADD-SUB-VALUE PIC S9(004) VALUE +2 COMP.
10 BIT8-MULT-VALUE PIC S9(004) VALUE +128 COMP.
10 BIT8-ADD-SUB-VALUE PIC S9(004) VALUE +1 COMP.
05 REDEFINES MULT-ADD-SUB-VALUES.
10 BIT-ARITH-ENTRY OCCURS 8 TIMES.
20 MULT-VALUE PIC S9(004).
20 ADD-SUB-VALUE PIC S9(004).
******************************************************************
01 WS-WORK-FIELDS.
******************************************************************
05 COMPARE-WRK-FLD PIC S9(004) VALUE 0 COMP.
05 REDEFINES COMPARE-WRK-FLD.
10 FILLER PIC X(001).
10 COMPARE-WRK-BYTE PIC X(001).
88 BIT-IS-ON VALUE X'80' THRU X'FF'.
88 BIT-IS-OFF VALUE X'00' THRU X'7F'.
05 ADD-SUB-WRK-FLD PIC S9(004) VALUE 0 COMP.
05 REDEFINES ADD-SUB-WRK-FLD.
10 FILLER PIC X(001).
10 ADD-SUB-WRK-BYTE PIC X(001).
1 /
******************************************************************
LINKAGE SECTION.
******************************************************************
01 LK-PARM-LEN PIC S9(004).
88 LK-EXECUTED-FROM-PGM VALUE -1.
88 LK-EXECUTED-FROM-JCL VALUE +0 THRU +9999.
01 LK-PARM-DATA.
05 LK-TGT-BYTE PIC X(001).
05 LK-BIT-NBR PIC 9(001).
88 VALID-BIT-NBR VALUE +1 THRU +8.
05 LK-ACTION PIC X(001).
88 LK-TURN-BIT-ON VALUE '1'.
88 LK-TURN-BIT-OFF VALUE '0'.
88 LK-FLIP-THE-BIT VALUE 'F'.
88 VALID-ACTION VALUE '1' '0' 'F'.
1 /
******************************************************************
PROCEDURE DIVISION USING LK-PARM-LEN LK-PARM-DATA
******************************************************************
000-MAINLINE.
******************************************************************
PERFORM 8000-VALIDATE-PARM-INFO
IF RETURN-CODE = ZEROS
PERFORM 1000-MODIFY-BIT-VALUE
ELSE
IF LK-EXECUTED-FROM-JCL
DISPLAY 'ERROR IN THE PARM LIST. RETURN CODE SHOWS '
'THE PARM# IN ERROR'
DISPLAY ' '
DISPLAY 'RETURN CODE >' RETURN-CODE '<'
END-IF
END-IF
GOBACK
.
******************************************************************
1000-MODIFY-BIT-VALUE.
******************************************************************
*===> SAVE TARGET BYTE
*---------------------------------------------------------------
MOVE LK-TGT-BYTE TO COMPARE-WRK-BYTE
MOVE LK-TGT-BYTE TO ADD-SUB-WRK-BYTE
*---------------------------------------------------------------
*===> ISOLATE BIT TO BE CHANGED. MULTIPLY THE TGT BYTE BY THE
*===> BINARY VALUE IN THE TABLE (POINTED TO BY THE BIT NUMBER
*===> PASSED BY THE CALLER). THIS MOVES THE TGT BIT TO THE HI
*===> ORDER POS OF THE WRK BYTE.
*---------------------------------------------------------------
COMPUTE COMPARE-WRK-FLD = COMPARE-WRK-FLD
* MULT-VALUE(LK-BIT-NBR)
*---------------------------------------------------------------
*===> CHANGE THE BIT AS DIRECTED BY THE ACTION FLD PROVIDED BY
*===> CALLER.IF THE BYTE VALUE OF COMPARE-WRK-BYTE IS > X'7F',
*===> THE REQUESTED BIT IS ONE;IF <= THE BIT IS ZERO.
*===> ADD TABLE VALUE IF BIT IS ZERO(OFF); SUB IF IT'S ONE(ON).
*===> THIS PREVENTS CHANGES TO SURROUNDING BITS WHILE CHANGING
*===> THE REQUESTED BIT.
*---------------------------------------------------------------
EVALUATE TRUE
WHEN LK-TURN-BIT-ON
IF BIT-IS-OFF
COMPUTE ADD-SUB-WRK-FLD = ADD-SUB-WRK-FLD
+ ADD-SUB-VALUE(LK-BIT-NBR)
END-IF
WHEN LK-TURN-BIT-OFF
IF BIT-IS-ON
COMPUTE ADD-SUB-WRK-FLD = ADD-SUB-WRK-FLD
- ADD-SUB-VALUE(LK-BIT-NBR)
END-IF
WHEN LK-FLIP-THE-BIT
IF BIT-IS-ON
COMPUTE ADD-SUB-WRK-FLD = ADD-SUB-WRK-FLD
- ADD-SUB-VALUE(LK-BIT-NBR)
ELSE
COMPUTE ADD-SUB-WRK-FLD = ADD-SUB-WRK-FLD
+ ADD-SUB-VALUE(LK-BIT-NBR)
END-IF
END-EVALUATE
*---------------------------------------------------------------
*===> IF SUBPGM WAS EXECUTED FROM JCL, I.E. A TEST, DISPLAY
*===> THE BEFORE AND AFTER VALUES OF THE TARGET FIELD. ELSE
*===> MOVE IT TO THE LINKAGE FIELD FOR RETURN TO THE CALLER.
*---------------------------------------------------------------
IF LK-EXECUTED-FROM-JCL
DISPLAY 'THE TARGET BYTE WAS CHANGED FROM >'
LK-TGT-BYTE '< TO >' ADD-SUB-WRK-BYTE '<'
ELSE
MOVE ADD-SUB-WRK-BYTE TO LK-TGT-BYTE
END-IF
.
******************************************************************
8000-VALIDATE-PARM-INFO.
******************************************************************
EVALUATE TRUE
WHEN LK-BIT-NBR NOT NUMERIC
WHEN NOT VALID-BIT-NBR
MOVE 3 TO RETURN-CODE
WHEN NOT VALID-ACTION
MOVE 4 TO RETURN-CODE
END-EVALUATE
.
*===> END OF PGM CODE |
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Sahoo
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Joined: 08 Jun 2006
Posts: 53
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| Do any body else know ? What is the exact difference? |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19244
Location: Inside the Matrix
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Hello,
| Quote: |
| What is the exact difference? |
You read the answer above. . .
Here it is again:
| Quote: |
START -- Start Assembly
The START instruction may be preceded by listing control
instructions and comments cards. The same label may not be used on a
START statement and a later CSECT statement.
CSECT -- Identify Control Section
No more than one CSECT may use a given symbol as a name,
and statements from different CSECT's may not be interspersed.
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