Here are ten things I learned about COBOL.

(1) Programs have four "division"s:

    IDENTIFICATION DIVISION.
    AUTHOR.
        WM MITCHELL.
    
    ENVIRONMENT DIVISION.
    SOURCE-COMPUTER.
    IBM-360.

    DATA DIVISION.
    ...
    
    PROCEDURE DIVISION.
    ...

(2) Here's a description of the format of payroll records (probably punched cards) that
    might appear in the DATA DIVISION.
        FD PAYROLL-FILE.
        01 PAYROLL-RECORD.
           05 I-PAYROLL-NUMBER  PIC X(5).
           05 I-NAME            PIC X(20).
           05 I-HOURS-WORKED    PIC 99V9
           05 FILLER            PIC XXX
           05 I-PAYRATE         PIC 99V999.
           05 I-DEPENDENTS      PIC 99.
           05 FILLER            PIC X(42).

    Each time a record is read from PAYROLL-FILE, the data from the various pieces of
    that record is read into the six variables (I-PAYROLL-NUMBER, etc.).  "FILLER" fields
    are ignored; no data is moved.

(3) Here's how to read a record from PAYROLL-FILE:
        READ PAYROLL-FILE
            AT END MOVE 'Y' TO W-OUT-OF-CARDS-FLAG.

    Note the assigment of 'Y' to W-OUT-OF-CARDS-FLAG when end-of-file is reached.

(4) 'PIC X(5)', a shorthand for 'PICTURE XXXXX', specifies a five-character field with
    no constraints on the data.

(5) 'PIC 99V9' specifies three digits of input with a decimal point ASSUMED between the
    second and third digits.  Thus, '123' would be interpreted as 12.3.  Similarly,
    the 'PIC 99V999' for I-PAYRATE means that '52812' would be interpreted as 52.812.

    (Remember that when COBOL was created, memory was many millions of times more expensive
    than today.  A PIC like 99V9 vs. 99.9 reduces memory usage by 25%!)

(6) Here's an example of a PROCEDURE DIVSION with two paragraphs, with line numbers added:
   
     1      PROCEDURE DIVISION:
     2          FINAL-TOTAL-PROCESSING.
     3              PERFORM ACCOUNT-TOTAL-PROCESSING.
     4              MOVE FINAL-TOTAL TO FINAL-TOTAL-OUT.
     5              PERFORM LINE-OUT.
     6  
     7          ACCOUNT-TOTAL-PROCESSING.
     8              MOVE PREVIOUS-ACCOUNT-NUMBER TO ACCOUNT-NUMBER-OUT.
     9              MOVE ACCOUNT-TOTAL TO ACCOUNT-TOTAL-OUT
    10              PERFORM LINE-OUT
    11              MOVE ACCOUNT-NUMBER TO PREVIOUS-ACCOUNT-NUMBER
    12              MOVE ZERO TO ACCOUNT-TOTAL.

    The paragraphs are a bit like functions/procedures, but they have no parameters.  Note that lines
    3, 5, and 10 perform other paragraphs.

    At line 12, "MOVE ZERO ..." is used to zero ACCOUNT-TOTAL.

    The variables ACCOUNT-NUMBER-OUT, ACCOUNT-TOTAL-OUT, and FINAL-TOTAL-OUT are fields in an
    FD (file description) for an output file.
    
(7) Here's code that executes the code in one of two "paragraphs" based on the value of
    HOURS-WORKED: 

    IF I-HOURS-WORKED IS GREATER THAN 40
        PERFORM OVERTIME-ROUTINE.
    ELSE
        PERFORM NORMAL-ROUTINE.

    Note that variable names can contain hyphens, and "IS GREATER THAN 40" is
    English.

(8) Here's an example of opening two files:
    OPEN INPUT BALANCE-FORWARD-FILE.
    OPEN OUTPUT INVENTORY-LISTING.

(9) Some examples of math:
    ADD X, Y, Z, GIVING SUM

    ADD 1 TO ITEM-COUNT

    ADD A, B TO C, D     (adds A+B to both C and D)

    MULTIPLY 4 BY A
    
(10) EXAMINE can count and/or replace occurrences of characters.  If SAMPLE is
    '0016047', then
        EXAMINE SAMPLE TALLYING LEAD '0' REPLACING BY '*'
    will change SAMPLE to '**16047' and put 2 in the "register" TALLY.

    If SAMPLE is 'PT890NQ9'
        EXAMINE SAMPLE TALLYING UNTIL FIRST 'Q'
    would put 6 in TALLY.

    INSPECT is similiar to EXAMINE, but more powerful.  Example:
        INSPECT SAMPLE TALLYING INDEX-4 FOR LEADING SPACES
            REPLACiNG ALL '.' BY ',', FIRST 'Q' BY 'P'.

(11) PERFORM, MOVE, EXAMINE are "verbs", but IF ..., ADD ..., and MULTIPLY ... are
    considered to be "statements".

(12) Here's an example of getting a quote into a variable

    MOVE 'THOMAS M. O' QUOTE 'REILLY' to FULL-NAME.
    
Yes, that's twelve things, not ten--I got carried away!  Maybe you'll get carried away, too!    

Sources:
    A Simplified Guide to Structured COBOL Programming by Daniel D. McCracken
    Standard COBOL, 2nd edition, Mike Murach