Follow Schofield's Three Laws of Computing and avoid disasters

Follow Schofield's Three Laws of Computing and avoid disasters

Summary: These "Laws", developed over three decades, may highlight things you're doing wrong, or help you avoid the worst screw-ups. Violate them at your peril…


The New Year is a good time to think about how you are going to approach things over the next year, and preferably the next few decades. When I do this, I use Schofield's Three Laws of Computing, and you may find them useful. They're not really Laws and they're not new -- the first dates back to the 1980s -- and I have written about them before in the Guardian, but not here.

Schofield's First Law of Computing states that you should never put data into a program unless you can see exactly how to get it out.

This law was first framed when I had data on 8-inch CP/M floppy disks, 5.25-inch Apple and Atari diskettes, and various other media. Today it would obviously include cloud storage.

Many people spend a lot of time worrying about which PC, tablet or phone to buy, when they might only use it for 18 months to 3 years. Hardware is transitory, and rapidly becomes either scrap or landfill. It's much more important to think about software -- which often lasts for decades -- and data, which might well outlive you. Data is forever.

This law is particularly important when data costs much more than either hardware or software. Just estimate how much it would cost to retype or recreate data rather than import it.

The most monumental errors arise from ignoring the First Law. One example was the BBC's Domesday discs, which were created to run on 8-bit Acorn BBC micros in UK schools and public libraries. This was supposed to be a new version of the 1,000-year-old Domesday Book, but both the computer and the video discs rapidly became obsolete, making the data inaccessible. It was rescued, as I wrote here, but it would have been much more sensible to use a commodity hardware platform and open (or at least ubiquitous) file formats.

Schofield's Second Law of Computing states that data doesn't really exist unless you have at least two copies of it.

If you only have one copy of something, it's a bit like Schrödinger's cat. Is it alive or dead? You have to look in the box to find out. In the same way, you'd have to load your single copy of a file or database to see if it was "live" data or corrupted (dead) or had simply disappeared. (Perhaps you deleted it by mistake or forgot where you stored it.)

Ideally, you should have at least three copies of everything, preferably on different media. It is a good idea to store one copy in the cloud, as then you have data "off premise" -- buildings have been known to flood or burn down -- as long as it's not your only copy. Having three copies means you can do file comparisons and therefore check if one of them has been corrupted.

Schofield's Third Law of Computing states that the easier it is for you to access your data, the easier it is for someone else to access your data.

In the days when everything was on an inaccessible mainframe and backed up on tape, data rarely went walkies. Nowadays, important business data can be stolen using a tiny SD card or USB memory stick, or lost when a smartphone is left in the back of a cab, or a laptop is left on a train. Data stored in the cloud may be vulnerable to hacking, especially if the hacker has physical access to a hard drive where the user has stored passwords for easy access.

Samsung smartphone
You get a nice new Samsung smartphone, but do you know where your data lives, or the file formats used to store it? Photo credit: Samsung

Having access to someone's web-based email account can be as good as having their smartphone or laptop, and sometimes better. People often email themselves important files, or store them in a related Gdrive or SkyDrive. Further, some simple searching will usually fish out loads of plain text passwords. If not, you can easily get a password reset, unless the account uses two-factor security.

The proliferation of poorly-protected, unencrypted BYOD hardware and cloud services may mean there is now less chance of losing data under the Second Law, but more chance of losing it under the Third Law.

The First Law reflects the 1980s when there was a huge variety of hardware and software, and the Second Law reflects the 1990s, when people relied on cheap hard drives that were rarely backed up properly. The need for the Third Law came with the proliferation of devices and web-based services in the 2010s. However, I don't yet see the need for a Fourth Law -- though I'm open to suggestions. The First Law already covers the growth of incompatible cloud services that work like lobster pots, or the Hotel California.

In a better world, I'd be able to advise people not to put data into a cloud service unless they could export it to a different cloud service without downloading it, possibly reformatting it, then re-uploading it. Until you can do that, the idea of having everything in the cloud is, frankly, insane.

Topics: Security, Data Management

Jack Schofield

About Jack Schofield

Jack Schofield spent the 1970s editing photography magazines before becoming editor of an early UK computer magazine, Practical Computing. In 1983, he started writing a weekly computer column for the Guardian, and joined the staff to launch the newspaper's weekly computer supplement in 1985. This section launched the Guardian’s first website and, in 2001, its first real blog. When the printed section was dropped after 25 years and a couple of reincarnations, he felt it was a time for a change....

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  • Rules of Thumb

    Because these are observation drawn from decades of observation and experience, I take them to heart. As rules to compute by.
    They, as articulated are sound and reasonable principles, certainly.
    Tho' anecdotes are legion to underscore your warnings and accumulated wisdom, I'd like to share one little one. Because it's so poster boy representative.
    A 'Street Person' acquaintance of mine had a stash of phones he found along his walking, over time. Could I evaluate and perhaps generate some cash? Sure.
    Two top end BBs in the bunch. Because I just don't know when to give up, I decided to try again to charge these so dead phones. One strangely, after long charge attempts, came to life. I retrieved a number reaching our City Hall. The short of this is that 'Kyle' had lost it two years ago. 'A lot more careful now about back ups.'
    But the man predictably said that, 'The phone is replaceable, only dollars.' But the 8G Mini SD Card had pics and videos galore of his one Boy's childhood. As well as some confidential City Data. 'I wept when I realized I'd lost it in the snow.'
  • needed reminders...

    These 3 laws are very obvious when thought about, but unfortunately no where near enough folks THINK about the placement/storage of data/personal info.
    Old Dog V
  • Coppola?

    Wasn't it Coppola who lost all his screen plays and manuscripts, when his house was burgled and they stole his computer and the backup disks?

    One customer decided that a mirrored server meant that they didn't need external backups. That worked fine, until some critical files became corrupted. Guess what, the corruption was automatically mirrored!
  • Domesday

    I remember going to see one of the original BBC Domesday sites in West Dean College, Chichester. As far as I know, the system was ported and is still available from the site as well as from the BBC's 'reloaded' archives.

    It had a lot of problems with its file system, whatever that was. Half of it didnt work properly even when new, searches brought up text but no pictures on many queries and what was there was severely limited compared to the millions of hits one gets by Googling today.

    A few years ago I decided to do something about my collection of old computers and put it on eBay. A Sharp MZ701 with a working plotter went quickly and wound up in a museum in Ireland. The original 'Rock Lobster' Amiga board along with it's funny-format 3 1/4" floppy drive was next, but the real surprise turned out to be the early issues of Practical Computing...

    A couple of collectors got into a war over issue 2 and I got 25 quid for that!

    Practical Computing was an inspiration to me after I encountered a BBC Micro model A hidden away in the Careers Office at school and asked if I could use it - only the head of mathematics had ever touched it and he didnt know how to use it properly. 'Knock yourself out lad, stupid thing that is.' he told me as he showed me how to switch it on. Seems he was wrong about how popular it would be over 30 years and nearly as many languages later.

    Much regard,
  • Thanks for the memories!

    I edited Practical Computing in the early 1980s but I don't have all the issues before that. I do remember buying issues that were unmissable because of the serial, The Hexadecimal Kid ;-)

    I was also one of the thousands who contributed an essay to the Domesday Disc, though I've long since forgotten what. In the post above, there's a link to a story I wrote about archiving at Kew and the university project to rescue Domesday data, and also a link to a ZDNet story about a Domesday system installed last year at TNMOC in Bletchley Park.
    Jack Schofield
  • Cloudsourcing lessons

    If you were an early adopter of technology as I was in the mid 90s you'll remember the early attempts of cloudsourcing. Geocities was the great new wave of interactive media. I had a great amount of effort into putting my poetry and short-stories on the web in html format. I even had made triplicate copies on angelfire and tripod just in case something ever happened to geocities. It was subsequently purchased by Yahoo! And dismantled as a threat to their business model.
    Another cloudsourcing experiment I engaged in during the late 90s was where I had my music uploaded, perhaps a gigabyte of data when at the time my whole harddrive was 8 gigs. Then the dot-com bubble burst and combined with new RIAA rulings the whole site and concept got tossed around companies like a game of hot-potato. When I asked the company that owns that data about it the customer service assured me that no one but no one has access to it now beside the bigwig executives at a company that didn't even exist yet when I uploaded it.
    My big lesson is this: your intellectual property is only as safe as the company which owns the physical hardware it resides on. If and when that company folds your IP is then a commodity and perhaps a liability to the new company.
  • Obvious now but not in the era they were first thought about

    Like Jack I stored data on 8-inch and 5.25 inch floppy disks and before that on paper tape. I still have some of the data dating back to the 70's and 80's and some from much earlier, mostly photo's dating back to the Victorian era. Much of the photographic data is useless because there was no written information to go with it so I have no idea who or what is in the picture. I wonder how many of us have lots of photos stored without any written details. I have slides from the 60's that I know where they were taken but cannot remember some of the people in them. So is this data worth any more than that stored on other obsolete media such as Philips Video discs used for the BBC Doomsday Project or personal letters still only stored on 8 inch floppy disks or data backups on QIC (quarter inch cartridge tape).
    I still keep my data backup as I did back in the days of floppy disk, "Grandfather, father, son" copies but now also on different physical media with some important stuff encrypted on different cloud based storage. I still ask myself how much of it will still be available to my grandchildren or great grandchildren and will it be interesting perhaps to historians in the centuries to come? I can still read documents written with quill pen more than 1000 years old and learn how people lived then. Will our ancestors be able to do the same with some of the data we are saving?