Comtran
COMTRAN (COMmercial TRANslator) is an early programming language developed at IBM.
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It was intended as the business programming equivalent of the scientific programming language FORTRAN (FORmula TRANslator). It served as one of the forerunners to the COBOL language. Developed by Bob Bemer, in 1957, the language was the first to feature the programming language element known as a picture clause.
| Developer | Bob Bemer |
|---|---|
| First appeared | 1957 |
| Influenced by | |
| FLOW-MATIC | |
| Influenced | |
| COBOL | |
Contributions to COBOL
Several elements of COMTRAN were incorporated into COBOL:
- Picture clause.
- Paragraphing: dividing code into paragraphs (with line breaks not significant).
- Paragraph names. Assigning names to paragraphs, and jumps (
GO TO's) are to a paragraph name, not to a line number. AT ENDclause on file input operations.- Figurative constant
HIGH-VALUE. - Passing a numeric value (
RETURN-CODE) back to the operating system when the program terminates.
Picture clause
A picture clause element defines how a particular data item should be formatted, for output. It consists of a string of letters and digits. It is similar to the FORTRAN format specifier seen in the READ and WRITE statements, or the formatting strings seen in more modern languages like C. This became an important part of COBOL.
Sample program
This is a sample COMTRAN program, doing payroll calculations.
01001 *PROCEDURE 01002 CALL (EMPLOYEE.NUMBER) EMPLOYNO, 01003 (BONDEDUCTION) BONDEDUCT, 01004 (BONDENOMINATION) BONDENOM, 01005 (BONDACCUMULATION) BONDACCUM, 01006 (INSURANCE.PREM) INSPREM, 01007 (RETIREMENT.PREM) RETPREM, 01008 (DEPARTMENT.TOTAL) DPT. 01009 START. OPEN ALL FILES. 01010 GET.MASTER. GET MASTER, AT END DO END.OF.MASTERS. 01011 GET.DETAIL. GET DETAIL, AT END GO TO END.OF.DETAILS. 01012 COMPARE.EMPLOYEE.NUMBERS. GO TO COMPUTE.PAY WHEN DETAIL EMPLOYNO 01013 IS EQUAL TO MASTER EMPLOYNO, LOW.DETAIL WHEN DETAIL 01014 EMPLOYNO IS LESS THAN MASTER EMPLOYNO. 01015 HIGH.DETAIL. MOVE 'M' TO MASTER ERRORCODE, FILE MASTER IN 01016 ERROR.FILE. 01017 GET MASTER, AT END DO END.OF.MASTERS. 01018 GO TO COMPARE.EMPLOYEE.NUMBERS. 02001 LOW.DETAIL. MOVE 'D' TO DETAIL ERRORCODE, FILE DETAIL IN 02002 ERROR.FILE. 02003 GO TO GET.DETAIL. 02004 END.OF.MASTERS. IF DETAIL EMPLOYNO = HIGH.VALUE THEN GO TO 02005 END.OF.RUN OTHERWISE SET MASTER EMPLOYNO = HIGH.VALUE. 02006 END.OF.DETAILS. IF MASTEREMPLOYNO = HIGH.VALUE THEN GO TO 02007 END.OF.RUN OTHERWISE SET DETAIL EMPLOYNO = HIGH.VALUE, GO 02008 TO COMPARE.EMPLOYEE.NUMBERS. 02009 END.OF.RUN. MOVE CORRESPONDING GRAND.TOTAL TO PAYRECORD, FILE 02010 PAYRECORD, CLOSE ALL FILES. 02011 STOP 1234. 02012 COMPUTE.PAY. IF DETAIL HOURS IS GREATER THAN 40 THEN SET DETAIL 02013 GROSS = (DETAIL HOURS - 40) * MASTER RATE * 1.5. 02014 SET DETAIL GROSS = DETAIL GROSS + MASTER RATE * 40, DO 02015 FICA.ROUTINE, DO WITHHOLDING.TAX.ROUTINE. 02016 IF MASTER BONDEDUCT IS NOT EQUAL TO ZERO THEN DO 02017 BOND.ROUTINE. 02018 DO SEARCH FOR INDEX = 1(1)12. 02019 NET. SET PAYRECORD NETPAY = DETAIL GROSS - DETAIL FICA - DETAIL 02020 WHT -DETAIL RETIREMENT - DETAIL INSURANCE - DETAIL 02021 BONDEDUCT. References
Further reading
- IBM's Early Computers, by Charles Bashe, Lyle Johnson, John Palmer, and Emerson Pugh, 1986, MIT Press, ISBN 0-262-02225-7.
External links
- Genealogy Programmers Solve Y2K in 1958 Archived 2007-03-04 at the Wayback Machine
- IBM Commercial Translator General Reference Manual (pdf, 8.2M) Page 87.
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