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authorHunter Coleman <35200320+HColeman1@users.noreply.github.com>2020-05-02 14:20:19 -0500
committerAndrew Ryan Davis <AndrewDavis1191@gmail.com>2020-08-09 14:32:05 -0700
commit2d387a2aaee2253705598ac71ea8d3711ddda7eb (patch)
tree2be87d2d89af8dced94a99cf1728f44d8f76eacc /cobol.html.markdown
parent6f9f3e84ff8e9005f03edbbaac97a5e0b2719ca8 (diff)
Update to cobol.html.markdown
Fixed multiple errors in the COBOL tutorial.
Diffstat (limited to 'cobol.html.markdown')
-rw-r--r--cobol.html.markdown301
1 files changed, 149 insertions, 152 deletions
diff --git a/cobol.html.markdown b/cobol.html.markdown
index 4452bd95..7c68db7b 100644
--- a/cobol.html.markdown
+++ b/cobol.html.markdown
@@ -8,7 +8,7 @@ COBOL is a business-oriented language revised multiple times since its original
organizations.
```cobol
- *COBOL. Coding like it's 1985.
+ *COBOL. Coding like it's 1985.
*Compiles with GnuCOBOL in OpenCobolIDE 4.7.6.
*COBOL has significant differences between legacy (COBOL-85)
@@ -22,164 +22,161 @@ organizations.
*Legacy COBOL also imposes a limit on maximum line length.
*Keywords have to be in capitals in legacy COBOL,
*but are case insensitive in modern.
-
- *First, we must give our program ID.
+ *Although modern COBOL allows you to use mixed-case characters
+ *it is still common to use all caps when writing COBOL code.
+ *This is what most professional COBOL developers do.
+ *COBOL statements end with a period.
+
+ *COBOL code is broken up into 4 divisions.
+ *Those divisions, in order, are:
+ *IDENTIFICATION DIVSION.
+ *ENVIRONMENT DIVISION.
+ *DATA DIVISION.
+ *PROCEDURE DIVISION.
+
+ *First, we must give our program an ID.
*Identification division can include other values too,
- *but they are comments only. Program-id is mandatory.
- identification division.
- program-id. learn.
+ *but they are comments only. Program-id is the only one that is mandatory.
+ IDENTIFICATION DIVISION.
+ PROGRAM-ID. LEARN.
+ AUTHOR. JOHN DOE.
+ DATE-WRITTEN. 05/02/2020.
*Let's declare some variables.
- data division.
- working-storage section.
-
- *Variables are specified by a "picture" - how they should be
- *displayed, and variable type is inferred from this.
- *The "01" value is the level number which is used for building
- *data structures.
- 01 myname picture xxxxxxxxxx. *> A 10 character string.
- 01 age picture 999. *> A number up to 3 digits.
- 01 valx picture 999. *> Another number up to 3 digits.
+ *We do this in the WORKING-STORAGE section within the DATA DIVISION.
+ *Each data item (aka variable) with start with a level number, then the name of the item,
+ *followed by a picture clause describing the type of data that the variable will contain.
+ *Almost every COBOL programmer will abbreviate PICTURE as PIC.
+ *A is for alphabetic, X is for alphanumeric, and 9 is for numeric.
+
+ *example:
+ 01 MYNAME PIC xxxxxxxxxx. *> A 10 character string.
+
+ *But counting all those x's can lead to errors, so the above code can, and should,
+ *be re-written as:
+ 01 MYNAME PIC X(10).
+
+ *Here are some more examples:
+ 01 AGE PIC 9(3). *> A number up to 3 digits.
+ 01 LAST_NAME PIC X(10). *> A string up to 10 characters.
+
+ *In COBOL, multiple spaces are the same as a single space, so it is common
+ *to use multiple spaces to line up your code so that it is easier for other
+ *coders to read.
01 inyear picture s9(7). *> S makes number signed.
*> Brackets indicate 7 repeats of 9,
*> ie a 6 digit number (not an array).
- *Now let's write some code.
- procedure division.
-
- main-procedure.
- *> COBOL is the language that uses DISPLAY instead of PRINT.
- *> Note: no full stops after commands. Only after the LAST
- *> command.
- display "Hello. What's your name?"
-
- *> Let's input a string.
- *> If input too long, later characters are trimmed.
- accept myname
- display "Hello " myname *> We can display several things.
- display "How old are you?"
-
- *> Let's input a number.
- *> If input too long, EARLIER characters are trimmed.
- accept age
-
- display age *> Left-padded to three chracaters with zeroes,
- *> because of the defined PICTURE for age.
-
- *> We have two ways of doing a FOR loop.
- *> Old style way: doesn't give an index.
- perform age times
- display "*" with no advancing *> Ie, no newline at end
- end-perform
- display "." *> Output buffer isn't flushed until newline.
-
- *> New style way: with an index.
- perform varying valx from 1 by 1 until valx > age
- display valx "-" with no advancing
- end-perform
- display "."
-
- *> If tests are still good old if tests.
- if myname = "Bob" then
- display "I don't like Bob."
- else
- display "I don't know you."
- end-if
-
- *> There are two ways of doing subprograms and calling
- *> them.
- *> The simplest way: a paragraph.
- perform subparagraph
-
- *> The complex way, with parameters and stuff.
- call "eratosthenes" using age returning valx
-
- display "There were " valx " primes."
-
- stop run.
-
- subparagraph. *> Marks the top of an internal subprogram.
- *> Shares variable score with its caller.
-
- *> Read year from system timer.
- *> Remember the whole "year 2000 crisis"? The yyyyddd
- *> option was added in response to that.
- accept inyear from day yyyyddd.
-
- *> We can do math step-by-step like this...
- divide 1000 into inyear.
- subtract age from inyear.
-
- display "You were born in " inyear "."
-
- *> Or we can just use expressions.
- compute inyear = 1970 - inyear.
-
- if inyear >= 0 then
- display "When you were " inyear ", " with no advancing
- else
- display inyear " years before you were born, " with no
- advancing
- end-if
-
- display "COBOL was the most popular language in the world."
- . *> You can put the final . on a new line if it's clearer.
-
-
- *If we want to use a subprogram, we use literally a subprogram.
- *This is the entire program layout, repeated for the
- *eratosthenes subroutine.
- identification division.
- program-id. eratosthenes.
-
- data division.
- working-storage section.
- *Declare an array.
- *We can declare a variable to use as an index for it at the
- *same time.
- 01 sieve pic 9 occurs 999 times indexed by sa, sb.
- *> Standard cobol doesn't have a boolean type.
- 01 pstart pic 999.
- 01 counter pic 999.
-
- *Our parameters have to be declared in the linkage section.
- *Their pictures must match the values they're called with.
- linkage section.
- 01 maxvalue picture 999.
-
- *"using" declares our actual parameter variables.
- *"returning" declares the variable value returned at end.
- procedure division using maxvalue returning counter.
- main-procedure.
-
- display "Here are all the primes up to " maxvalue "."
-
- perform varying sa from 1 by 1 until sa > maxvalue
- move 1 to sieve (sa)
- end-perform
-
- perform varying sa from 2 by 1 until sa > maxvalue
- if sieve(sa) = 1 then
- compute pstart = sa + sa
- perform varying sb from pstart by sa until sb >
- maxvalue
- move 0 to sieve(sb)
- end-perform
- end-if
- end-perform
-
- initialise counter *> To zero by default for a number.
-
- perform varying sa from 2 by 1 until sa > maxvalue
- if sieve(sa) = 1 THEN
- display sa
- add 1 to counter
- end-if
- end-perform.
-
- end program eratosthenes.
-
- end program learn.
+ *Now let's write some code. Here is a simple, Hello World program.
+ IDENTIFICATION DIVISION.
+ PROGRAM-ID. HELLO.
+ DATA DIVISION.
+ WORKING-STORAGE SECTION.
+ 01 THE-MESSAGE PIC X(20).
+ PROCEDURE DIVSION.
+ DISPLAY "STARTING PROGRAM".
+ MOVE "HELLO WORLD" TO THE-MESSAGE.
+ DISPLAY THE-MESSAGE.
+ STOP RUN.
+
+ *The above code will output:
+ *STARTING PROGRAM
+ *HELLO WORLD
+
+
+
+ ********COBOL can perform math***************
+ ADD 1 TO AGE GIVING NEW-AGE.
+ SUBTRACT 1 FROM COUNT.
+ DIVIDE VAR-1 INTO VAR-2 GIVING VAR-3.
+ COMPUTE TOTAL-COUNT = COUNT1 PLUS COUNT2.
+
+
+ *********PERFORM********************
+ *The PERFORM keyword allows you to jump to another specified section of the code, and then to return to the next executable
+ *statement once the specified section of code is completed. You must write the full word, PERFORM, you cannot abbreviate it.
+
+ IDENTIFICATION DIVISION.
+ PROGRAM-ID. HELLOCOBOL.
+
+ PROCEDURE DIVISION.
+ FIRST-PARA.
+ DISPLAY 'THIS IS IN FIRST-PARA'.
+ PERFORM THIRD-PARA THRU FOURTH-PARA. *>skip over second-para and perfrom third and fourth
+ *> then after performing third and fourth, return here and continue the program until STOP RUN.
+
+ SECOND-PARA.
+ DISPLAY 'THIS IS IN SECOND-PARA'.
+ STOP RUN.
+
+ THIRD-PARA.
+ DISPLAY 'THIS IS IN THIRD-PARA'.
+
+ FOURTH-PARA.
+ DISPLAY 'THIS IS IN FOURTH-PARA'.
+
+
+ *When you compile and execute the above program, it produces the following result:
+ THIS IS IN FIRST-PARA
+ THIS IS IN THIRD-PARA
+ THIS IS IN FOURTH-PARA
+ THIS IS IN SECOND-PARA
+
+
+ **********Combining variables together using STRING ***********
+
+ *Now it is time to learn about two related COBOL verbs: string and unstring.
+
+ *The string verb is used to concatenate, or put together, two or more stings. Unstring is used, not surprisingly, to separate a *string into two or more smaller strings. It is important that you remember to use ‘delimited by’ when you
+ *are using string or unstring in your program.
+
+ IDENTIFICATION DIVISION.
+ PROGRAM-ID. LEARNING.
+ ENVIRONMENT DIVISION.
+ DATA DIVISION.
+ WORKING-STORAGE SECTION.
+ 01 FULL-NAME PIC X(20).
+ 01 FIRST-NAME PIC X(13) VALUE "BOB GIBBERISH".
+ 01 LAST-NAME PIC X(5) VALUE "COBB".
+ PROCEDURE DIVISION.
+ STRING FIRST-NAME DELIMITED BY SPACE
+ " "
+ LAST-NAME DELIMITED BY SIZE
+ INTO FULL-NAME
+ END-STRING.
+ DISPLAY "THE FULL NAME IS: "FULL-NAME.
+ STOP RUN.
+
+
+ *The above code will output:
+
+ THE FULL NAME IS: BOB COBB
+
+
+ *Let’s examine it to see why.
+
+ *First, we declared all of our variables, including the one that we are creating by the string command, in the DATA DIVISISION.
+
+ *The action takes place down in the PROCEDURE DIVISION. We start with the STRING keyword and end with END-STRING. In between we *list what we want to combine together into the larger, master variable.
+ *Here, we are combining FIRST-NAME, a space, and LAST-NAME.
+
+ *The DELIMITED BY phrase that follows FIRST-NAME and LAST-NAME tells the program how much of each variable we want to capture.
+ *DELIMITED BY SPACE tells the program to start at the beginning, and capture the variable until it runs into a space.
+ *DELIMITED BY SIZE tells the program to capture the full size of the variable.
+ *Since we have DELIMITED BY SPACE after FIRST-NAME, the GIBBERISH part is ignored.
+
+ *To make this clearer, change line 10 in the above code to:
+
+ STRING FIRST-NAME DELIMITED BY SIZE
+
+ *and then re-run the program. This time the output is:
+
+ THE FULL NAME IS: BOB GIBBERISH COBB
+
+
+
+
+
```