So whatever your faith or philosophy, I hope you have a great time and that the new year brings you everything you seek.

So I figured I’d try packaging and a couple of hours later and I’ve a copy in my PPA. I’m unsure who maintains the packaging guide so I wanted to say thank you on Ubuntu Planet hoping those involved see it. Its great when you want to try something, find comprehensive instructions and can wrap it up in a few hours.

COmmon Business Oriented Language (COBOL) 85 standard was the first language I was taught. Napier University was a feeder into the banking and insurance industries in Edinburgh at the time and they had sizeable COBOL farms. It proved profitable too, as a number of students I knew went to the US to alleviate Y2K bugs in thousands of legacy applications. COBOL had fallen out of favour in US colleges.

I was talking to someone the other day who mentioned that he maintains COBOL legacy applications. Apparently things have gone full circle for the UK, where COBOL is no longer taught so his company outsources to India. I’m not overly surprised COBOL is dying out as an educational tool because as languages go its not like much else – Dijkstra certainly didn’t rate it:

The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offence.

Who am I to argue with the man who killed the goto statement? Certainly as a language it has issues – the 86 standard wasn’t totally compatible with the previous 74 standard; it has no functions; and it has no pointers. Then again it was in part based around the work of Rear Admiral Grace Hopper, the coolest woman ever in computer science, so it couldn’t be all bad could it? She believed that programming languages in mathematical notation were generally not well understood – COBOL is about as self documenting as it gets. It is a product of its time – for example the first six columns are reserved for sequence numbers, this came about as forms were used to write programs which were in turn converted to punch cards.

An example is the best way to explain this, so I decided to revisit Project Euler’s first problem and code it in COBOL, something I haven’t touched in years. As Rear Admiral Grace Hopper said:

It’s easier to ask for forgiveness than it is to get permission.

Of course we need a compiler, Ubuntu has Open COBOL available:

sudo apt-get install open-cobol

Lets consider the problem again:

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

My solution is to iterate through every number from 1 to 1000, test if it divides by 3 or 5 without a remainder and if so then add it to a counter. In pseudocode:

For counter = 1 to 1000 Step 1
    If counter % 3 = 0 or number % 5 = 0 Then
        total = total + counter
    End If
End For
Display total

But wait – this is COBOL, a language that doesn’t include the word “terse”. So let’s adapt this to a more verbose piece of pseudocode:

For counter = 1 To 1000
    If counter % 3 = 0 Then
        Set flag To TRUE
    End If
    If counter % 5 = 0 Then
        Set flag To TRUE
    End If
    If flag = TRUE Then
        total = total + counter
        Set flag To FALSE
    End If
    Display total
End For

Right, here we go. Its been a long time.  COBOL is organised into divisions, sections, paragraphs, sentences and statements – all are terminated by a period. There are four divisions:

• Identification. Unsurprisingly contains information about the program.
• Environment. This isn’t initially obvious but is concerned with portability – this section allows you to isolate anything that is platform specific. So in theory only the environment division needs changing between platforms.
• Data. This holds all the variables and has four sections – file (file handling); linkage (used with sub-routines); report (for report writers); and the one you almost always need, working-storage (where all your working variables are).
• Procedure. Guess what? Yes this is where the program itself is.

        IDENTIFICATION DIVISION.
        PROGRAM-ID. EULER_PROBLEM_ONE.

Not much explanation required there then. We don’t need an environment division, it doesn’t hurt to populate the division name anyway.

The next division requires a little more explanation. We need a working-storage section but COBOL defines variables using level, name, picture clause and optionally a value.

Picture clauses define a variable’s format. Levels allow data to be grouped, for example if you defined a student as having an ID and a name you might have:

01 student.
    02 identifier          PIC A9(7).
    02 name                PIC A(30).

Level numbers are for the most part arbitrary as long as the lower the number the higher the level, with the exception of 66 (deprecated), 77 (individual elements) and 88 (used to define conditions). Picture clauses can use: 9 (digit); A (letter); X (digit or letter); V (decimal point); S (sign). You can use A(30) rather than typing loads of A’s.

That just leaves us a procedure division. If you have ever coded assembler then you’ll probably find this easier than if you’ve used C. You need to describe every step. The main iteration construct we need from our pseudocode is a For Loop. COBOL has a PERFORM statement, you need to increment your counter yourself:

PERFORM UNTIL counter = 3
    ADD 1 TO counter GIVING counter
END-PERFORM.

A general convention is to use upper-case for reserved words and lower-case for variables. Pretty much all operations follow this command’s format – do something (ADD 1) to something (counter) and store it somewhere (counter).

IF condition1 > condition2 THEN
   STATEMENT
ELSE
   STATEMENT
END-IF.

You can nest if statements (there’s no Else If statement). Its not uncommon to find a lot of legacy code that only uses IF statements, why I don’t know because it has a Case statement called EVALUATE.

That just leaves us assignment:

MOVE value TO variable

Putting it all together, you need variables to Hold temporary values used to calculate answers, I always call it junk:

        IDENTIFICATION DIVISION.
        PROGRAM-ID. EULER_PROBLEM_ONE.

        ENVIRONMENT DIVISION.

        DATA DIVISION.
        WORKING-STORAGE SECTION.
        01 total        PIC 999999     VALUE 0.
        01 counter      PIC 9999       VALUE 1.
        01 junk         PIC 999999     VALUE 0.
        01 flag         PIC 9          VALUE 0.

        PROCEDURE DIVISION.
        PERFORM UNTIL counter = 1000
             COMPUTE junk = FUNCTION MOD (counter, 3)
             IF junk = 0 THEN
                 MOVE 1 TO flag
             END-IF
             COMPUTE junk = FUNCTION MOD (counter, 5)
             IF junk = 0 THEN
                MOVE 1 TO flag
             END-IF
             IF flag = 1 THEN
                ADD counter TO total GIVING total
                MOVE 0 TO flag
             END-IF
             ADD 1 TO counter GIVING counter
        END-PERFORM.
        DISPLAY total.
        STOP RUN.

Remember that indentation is important (despite the code formatting here not wanting to do it) – areas A and B take the first 6 characters so you need to begin in column 7.

Save the file as euler.cob, compile and run it:

cobc -x euler.cob
./euler

Giving the correct answer of 233168, albeit without any frills.

Hold on to your hats...

It took me a while to get this to compile – Open COBOL doesn’t care for the AUTHOR statement in the IDENTIFICATION DIVISION so I removed it.

What this snippet of code doesn’t show us is that larger projects are unbelievably verbose, lines and lines of code. Nor does it cover the hilarity of design using Data Flow Diagrams - queuing for hours to collect printouts from the University’s only 132 column printer.

Well that’s been a fun trip down memory lane, I don’t remember why I started this post.

Now get off my lawn.

I enjoy mathematics and programming, my degree modules have revolved around the two, covering Java and VB.Net (its a very Windows centric place the Open University but it’s getting better). I’m in the UK and would like to go back to Edinburgh for family reasons when I leave the services in a couple of years time. Looking at the job boards, there’s a lot of Java contracts in the area.

Has anyone got a job with only open source experience? Does anyone know of any open source projects that are Java based and would be a good starting point to build on the fundamentals? Are there other qualifications or courses that you recommend? What are employers looking for? Does anyone work in a specific field that utilises both maths and programming? Is there a language that is in particular demand or do you find that good experience is more value? What’s a realistic starting salary?

His answer? “Oh no that’s free, it’s bound to be rubbish.”

Strange, I thought he wanted Photoshop free.

Linux
If you’re using Linux, you’re probably a geek and don’t need some guy who blogs about manliness to tell you how to edit your host file.

Euler provides a series of programming challenges of increasing difficulty, as the student solves each in turn they gain experience of what does and does not work as well as confidence in their abilities. Importantly, the student is also applying programming to practical problems (if you’re a mathematics student) from the outset.

I’ll post my solutions here as I go. I’m aiming to do one a day but I’ll see how I get on. Not sure what language is best to get on with, Python is popular in open source circles but most of my courses are based around Java.

I’ve just started a maths course (MS221 with The Open University). I completed MST121 with a cheap Casio FX991 calculator (it cost about £15).

The time has come to buy something a bit more, well grown up. I’ve been looking at offerings from TI and HP. I’m kind of leaning towards an HP 50g. I can’t make up my mind so I thought I’d throw it out there and see what people recommend. The course says any calculator is allowed provided it doesn’t need plugged into the mains, doesn’t have a QWERTY (or local equivalent) keyboard and can’t communicate with other calculators.

Ideally it should be able to connect with Ubuntu – the HP has an SD card but I don’t know about TI.

I bought a new one (surprised that the hard disk size going up seems to have reduced any price decreases over time).

Seems like a faulty fan – sounds like a bearing grinding. Anyone any experience with them?