Author: Jo Brodie

https://twitter.com/JoBrodie same on BlueSky and other pages. Old photo!

Eggheads: helping us to visualise objects and classes

Ada the Egghead: a purple face with pinky purple hair
Ada the Egghead
Image by Daniel Gill for CS4FN

Past CS4FN articles have explored object-oriented programming through self-aware pizza and Strictly Come Dancing judges. But, if you’re one of those people who like to learn visually, it can be challenging to imagine what an object or class looks like. This article will hopefully help you to both think more about what makes this paradigm so useful as well as to give you a way to visualise objects.

To begin this adventure, I’d like to introduce Ada. Ada is an example of the newly discovered species egghead. Every egghead has very distinctive hair and eye colours. For example, Ada’s hair is a delightfully bright pink, and their eyes, a deep red. Despite their appearance, the egghead has a vicious roar intended to ward off predators, or indeed poachers.

Classes

As computer scientists, we might want to represent different eggheads in a program, but we don’t really want to store information about the eggheads with a written description or an image, because this would be harder than need-be for a computer to ‘understand’ (or rather to process as they don’t understand as such). Instead, we can store lots of individual features together, so that the computer can find out exactly what it needs from each egghead.

Egghead Name Hair Eyes Roar button
Egghead class. Image by Daniel Gill for CS4FN

One way to achieve this is by using a class. A class is a template which contains spaces for us to fill in details for the thing we want to represent. For the egghead, we might want to store data about their name, hair colour, and eye colour – then we can fill in the template for each of the eggheads we find. These individual features are often called attributes. In a program, these attributes would be represented with variables: a place where a value, a piece of data, is stored. We can visualise a class therefore as a box with gaps to fill in for the attributes like the one on the left.

From this image, you will see alongside the attributes, we also have an image of a button for roaring. As well as storing attributes, we also define behaviours. These are actions that we can perform on the thing being represented. We visualise any behaviour as such a button. For this example, we could imagine that pressing this button might provoke the egghead causing them to roar. In programming, a behaviour is represented by a procedure, some pre-defined code that when executed makes something happen. A button that causes something to happen is a simple way to visualise such procedures.

A key point to realise is that this class is simply a template – it isn’t storing any information, nor will the roar button work. We have no actual eggheads yet… That is where objects come in.

Objects

You may have noticed that I have been using the word thing to represent the actual thing (here eggheads) that we are representing with the class. This is to avoid using the word object, which has its own special meaning, in, you guessed it, object-oriented programming. If we want to actually use our class, we need to make an instance. That just means filling in the relevant details about the specific egghead we want to store. This instance is called an object.

Let’s imagine we want to store a representation of Ada in our program. We would take an instance of the Egghead class and fill in their details. The resulting object would represent Ada, whereas the class we started with represents all and any egghead that might ever exist. Below, you can see the objects for Ada and some of Ada’s friends; Alan and Edsger. We still visualise objects as boxes, just like classes, except now the gaps are all filled in.

Eggheads with values for the fields eg Ada Pink Red
Objects representing Ada, Alan and Edsger. Image by Daniel Gill for CS4FN

We (or a computer) could even take the given features of Alan and Edsger and generate an image of what they might look like. We have everything we need here to create something that looks and behaves like an egghead. This method of storing data means that a program can take whatever information it might want directly from the object. Likewise, it can do the equivalent of pressing the roar button and make each individual egghead roar.

Hiding the Details

Egghead with blue changed to orange
Trying to change Alan’s eye colour. Image by Daniel Gill for CS4FN

One thing we should consider while making the class is the integrity of the data. In its current form, any other part of our program, or another program using our class, can directly edit the attributes stored. Another part of the program (perhaps representing a virtual world for a virtual egghead to live in) might accidentally change the eye colour attribute for Alan, for example. This wouldn’t change Alan’s actual eye colour (which couldn’t happen anyway!), so our data would then be wrong. We can’t have that!

We can fix this by hiding the eye colour from the rest of the program, so it is stored within the object, but not accessible outside of it. But we still need a way for the program to read it: for this we use a button in our picture of the Egghead class. The existence of the eye colour attribute can then only be seen by other parts of the program by a procedure that gets the eye colour. No similar procedure is given for changing the eye colour, so there is no way to do it by mistake. Let’s build this new version of our class.

Sequence as values change
(a) Our new class, (b) An object representing Edsger, with eye colour hidden, (c) Pressing GetEyes gives us the eye colour. Image by Daniel Gill for CS4FN

This concept of hiding details is sometimes called encapsulation or information hiding, but computer scientists disagree about what these terms refer to exactly. Encapsulation is broader in its meanings, whereas information hiding is closer to what we are trying to do here. This video by ArjanCodes (see below) explains this distinction further.

We could change our class to include this concept for the name and hair colour, too. Whilst it is entirely possible for these attributes to change, it turns out that it is a good idea to hide them too: so hide name and use SetName and GetName buttons. That allows us to control the type of data we have going into that attribute (for example, checking the given name isn’t a number, which as all egghead names are made of letters would be a mistake).

Where next?

Now we have a class that represents all eggheads, we can store the details of any new egghead efficiently and safely. Hold on… some last-minute breaking news: scientists have found a new sub-species of egghead they are calling a rainbow egghead. All rainbow eggheads have rainbow hair, and a unique roar. Next time, we’ll use the concept of inheritance to give a more efficient way to write programs that store information about eggheads.

Daniel Gill, Queen Mary University of London

More on …

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Ethics – What would you do?

Signs pointing RIGHT to right and WRONG to the left
Right / Wrong image by Tumisu from Pixabay

You often hear about unethical behaviours, be it in politicians or popstars, but getting to grips with ethics, which deals with issues about what behaviours are right and wrong, is an important part of computer science too. Find out about it and at the same time try our ethical puzzle below and learn something about your own ethics…

Is that legal?

Ethics are about the customs and beliefs that a society has about the way people should be treated. These beliefs can be different in different countries, sometimes even between different regions of the same country, which is why it’s always important to know something about the local area when going on holiday. You don’t want to upset the local folk. Ethics tend to form the basis of countries’ laws and regulations, combining general agreement with practicality. Sticking your tongue out may be rude and so unethical, but the police have better things to do than arrest every rude school kid. Similarly, slavery was once legal, but was it ever ethical? Laws and ethics also have other differences; individuals tend to judge unethical behaviour, and shun those who behave inappropriately, while countries judge illegal behaviour – using a legal system of courts, judges and juries to enforce laws with penalties.

Dilemmas, what to do?

Now imagine you have the opportunity to go treading on the ethical and legal toes of people across the world from the PC in your home. Suddenly the geographical barriers that once separated us vanish. The power of computer science, like any technology, can be used for good or evil. What is important is that those who use it understand the consequences of their actions, and choose to act legally and ethically. Understanding legal requirements, for example contracts, computer misuse and data protection are important parts of a computer scientist’s training, but can you learn to be ethical?

Computer scientists study ethics to help them prepare for situations where they have to make decisions. This is often done by considering ethical dilemmas. These are a bit like the computer science equivalent of soap opera plots. You have a difficult problem, a dilemma, and have to make a choice. You suddenly discover you have a unknown long lost sister living on the other side of the Square, do you make contact or not, (on TV this choice is normally followed by a drum roll as the episode ends).

Give it a go

Here is your chance to try an ethical dilemma for yourself. Read the alternatives and choose what you would do in this situation. Then click on the poll choice. Like all good ‘personality tests’ you find out something about yourself: in this case which type of ethical approach you have in the situation according to some famous philosophers. There are also some fascinating facts to impress your mates. We’ll share the answers tomorrow.

Your Dilemma and your ethical personality

You are working for a company who are about to launch a new computer game. The adverts have gone out, the newspapers and TV are ready for the launch … then the day before you are told that there is a bug, a mistake, in the software. It means players sometimes can’t kill the dragon at the end of the game. If you hit the problem the only solution is to start the final level again. It can be fixed they think but it will take about a week or so to track it down. The computer code is hard to fix as it’s been written by 10 different people and 5 of them have gone on a back-packing holiday so can’t be contacted.

Peter McOwan, Queen Mary University of London

What the answers mean about you at the end!

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The answers

If you picked Option 1

1) Go ahead and launch. After all, there are still plenty of parts to the game that do work and are fun, there will always be some errors, and for this game in particular thousands have been signing up for text alerts to tell them when it’s launched. It will make many thousands happy.

That means you follow an ethical approach called ‘Act utilitarianism’.

Act Happy

The main principle of this theory, put forward by philosopher John Stuart Mill, is to create the most happiness (another name for happiness here is utility thus utilitarianism). For each situation you behave (act) in a way that increases the happiness of the largest number of people, and this is how you decide what is wrong or right. You may take different actions in similar situations. So you choose to launch a flawed game if you know that you have pre-sales of a hundred thousand, but another time decide to not launch a different flawed game where there are only one thousand pre-sales, as you wont be making so many people unhappy. It’s about considering the utility for each action you take. There is no hard and fast rule.

If you picked Option 2

2) Cancel the launch until the game is fixed properly, no one should have to buy a game that doesn’t work 100 per cent.

That means you follow an ethical approach called ‘Duty Theory’

Do your Duty

Duty theories are based on the idea of there being universal principles, such as ‘you should never ever lie, whatever the circumstances’. This is also known as the dentological approach to ethics (philosophers like to bring in long words to make simple things sound complicated!). The German philosopher Emanuel Kant was one of the main players in this field. His ‘Categorical Imperative’ (like I said long words…) said “only act in a way that you would want everyone else to act” (…simple idea!). So if you don’t think there should ever be mistakes in software then don’t make any yourself. This can be quite tough!

If you picked Option 3

3) Go ahead and launch. After all it’s almost totally working and the customers are looking forward to it. There will always be some errors in programs: it’s part of the way complicated software is, and a delay to game releases leads to disappointment.

You would be following the approach called ‘Rule utilitarianism’.

Spread a little happiness

Say something nice to everyone you meet today…it will drive them crazy

The main principle of this flavour of utilitarianism theory, put forward by philosopher Jeremy Bentham, is to create the most happiness (happiness here is called utility thus utilitarianism). You follow general rules that increase the happiness of the largest number of people, and this is how you decide what’s wrong or right. So in our dilemma the rule could be ‘even if the game isn’t 100% correct, people are looking forward to it and we can’t disappoint them’. Here the rule increases happiness, and we apply it again in the future if the same situation occurs.

Collaborative community coding & curating

Equality, diversity and inclusion in the R Project

Concentric Rings of rainbow people as triangles holding hands
Image by Gordon Johnson from Pixabay

You might not think of a programming language like Python or Scratch as being an ‘ecosystem’ but each language has its own community of people who create and improve its code (compilers, library code,…), flush out the bugs, introduce new features, document any changes and write the ‘how to’ guides for new users. 

R is one such programming language. It’s named after its two co-inventors (Ross Ihaka and Robert Gentleman) and is used by around two million people around the world. People working in all sorts of jobs and industries (for example finance, academic research, government, data journalists) use R to analyse their data. The software has useful tools to help people see patterns in their data and to make sense of that information. 

It’s also open source which means that anyone can use it and help to improve it, a bit like Wikipedia where anyone can edit an article or write a new one. That’s generally a good thing because it means everyone can contribute but it can also bring problems. Imagine writing an essay about an event at your school and sharing it with your class. Then imagine your classmates adding paragraphs of their own about the event, or even about different events. Your essay could soon become rather messy and you’d need to re-order things, take bits out and make sure people hadn’t repeated something that someone had already said (but in a slightly different way). 

When changes are made to software people also want to keep a note not just of the ‘words’ added (the code) but also to make a note of who added what and when. Keeping good records, also known as documentation, helps keep things tidy and gives the community confidence that the software is being properly looked after.

Code and documentation can easily become a bit chaotic when created by different people in the community so there needs to be a core group of people keeping things in order. Fortunately there is – the ‘R Core Team’, but these days its membership doesn’t really reflect the community of R users around the world. R was first used in universities, particularly by more privileged statistics professors from European countries and North America (the Global North), and so R’s development tended to be more in line with their academic interests. R needs input and ideas from a more diverse group of active developers and decision-makers, in academia and beyond to ensure that the voices of minoritised groups are included. Also the voices of younger people, particularly as many of the current core group are approaching retirement age.

Dr Heather Turner from the University of Warwick is helping to increase the diversity of those who develop and maintain the R programming language and she’s been given funding by the EPSRC* to work on this. Her project is a nice example of someone who is bringing together two different areas in her work. She is mixing software development (tech skills) with community management (people skills) to support a range of colleagues who use R and might want to contribute to developing it in future, but perhaps don’t feel confident to do so yet. 

Development can involve things like fixing bugs, helping to improve the behaviour or efficiency of programs or translating error messages that currently appear on-screen in the English language into different languages. Heather and her colleagues are working with the R community to create a more welcoming environment for ‘newbies’ that encourages participation, particularly from people who are in the community but who are not currently represented or under-represented by the core group and she’s working collaboratively with other community organisations such as R-Ladies, LatinR and RainbowR. Another task she’s involved in is producing an easier-to-follow ‘How to develop R’ guide.

There are also people who work in universities but who aren’t academics (they don’t teach or do research but do other important jobs that help keep things running well) and some of them use R too and can contribute to its development. However their contributions have been less likely to get the proper recognition or career rewards compared with those made by academics, which is a little unfair. That’s largely because of the way the academic system is set up. 

Generally it’s academics who apply for funding to do new research, they do the research and then publish papers in academic journals on the research that they’ve done and these publications are evidence of their work. But the important work that supporting staff do in maintaining the software isn’t classified as new research so doesn’t generally make it into the journals, so their contribution can get left out. They also don’t necessarily get the same career support or mentoring for their development work. This can make people feel a bit sidelined or discouraged. 

To try and fix this and to make things fairer the Society of Research Software Engineering was created to champion a new type of job in computing – the Research Software Engineer (RSE). These are people whose job is to develop and maintain (engineer) the software that is used by academic researchers (sometimes in R, sometimes in other languages). The society wants to raise awareness of the role and to build a community around it. You can find out what’s needed to become an RSE below. 

Heather is in a great position to help here too, as she has a foot in each camp – she’s both an Academic and a Research Software Engineer. She’s helping to establish RSEs as an important role in universities while also expanding the diversity of people involved in developing R further, for its long-term sustainability.

Further reading

Related careers

QMUL

Below is an example of a Research Software Engineer role which was advertised at QMUL in April 2024 – you can read the original advert and see a copy of the job description / person specification information which is archived at the “Jobs in Computer Science” website. This advert was looking for an RSE to support a research project “at the intersection of Natural Language Processing (NLP) and multi-modal Machine Learning, with applications in mental health.”

Closed, QMUL, Research Software Engineer (0.5FTE), ~£63.6k pro rata, closed April 2024

QMUL also has a team of Research Software Engineers and you can read about what they’re working on and their career here (there are also RSEs attached to different projects across the university, as above).

Archived job adverts from elsewhere

Below are some examples of RSE jobs (these particular vacancies have now closed but you can read about what they were looking for and see if that sort of thing might interest you in the future). The links will take you to a page with the original job advert + any Job Description (JD – what the person would actually be doing) and might also include a Person Specification (PS – the type of person they’re looking for in terms of skills, qualifications and experience) – collectively these are often known as ‘job packs’.

Note that these documents are written for quite a technical audience – the people who’d apply for the jobs will have studied computer science for many years and will be familiar with how computing skills can be applied to different subjects.

1. The Science and Technology Facilities Council (STFC) wanted four Research Software Engineers (who’d be working either in Warrington or Oxford) on a chemistry-related project (‘computational chemistry’ – “a branch of chemistry that uses computer simulation to assist in solving chemical problems”) 

2. The University of Cambridge was looking for a Research Software Engineer to work in the area of climate science – “Computational modelling is at the core of climate science, where complex models of earth systems are a routine part of the scientific process, but this comes with challenges…”

3. University College London (UCL) wanted a Research Software Engineer to work in the area of neuroscience (studying how the brain works, in this case by analysing the data from scientists using advanced microscopy).

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CS4FN Advent Calendar – Day 25 bonus Christmas crackers: have you ever seen this cracker joke?

If you’re pulling a Christmas cracker today look out for this now famous but fairly puzzling ‘joke’ –

Q: What kind of cough medicine does Dracula take?
A: Con medicine

Apart from the fact that the joke is more suited to Hallowe’en (I wonder when someone will invent Hallowe’en crackers!) ‘con medicine’ doesn’t make any sense as an answer. Over the years lots of people found this joke in their cracker then posted a photograph on social media asking if anyone got the joke and could explain it.

From 2015

From 2016
Still baffling folk in 2018…

An explanation from Andrew Taylor seems to have solved the mystery. The answer is probably coffin medicine (though even then it’s still not a particularly great joke, in keeping with the traditions of Christmas cracker jokes). Where has the ‘ffi‘ gone though? Read Andrew’s 2018 blog post ‘Con Medicine‘ to find out how a typographical quirk in the way some fonts / typefaces display those letters probably resulted in a simple error in printing.

Perhaps the error has been fixed and no-one will find it in their crackers this year!

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CS4FN Advent 2023 – Day 25: Merry Christmas! Today’s post is about the ‘wood computer’

Today is the final post in our CS4FN Christmas Computing Advent Calendar – it’s been a lot of fun rummaging in the CS4FN back catalogue, and also finding out about some new things to write about.

Advert for our Advent calendar
Image drawn and digitised by Jo Brodie.

Each day we’ve published a blog post about computing with the theme suggested by the picture on the advent calendar’s ‘door’. Our first picture was a woolly jumper so the accompanying post was about the links between knitting and coding, the door with a picture of a ‘pair of mittens’ on led to a post about pair programming and gestural gloves, a patterned bauble to an article about printed circuit boards, and so on. It was fun coming up with ideas and links and we hope it was fun to read too.

We hope you enjoyed the series of posts (click on any of the Christmas trees in this post to see them all) and that you are already having a very Merry Christmas.

And on to today’s post which is inspired by the picture of a Christmas Tree, so it’ll be a fairly botanically-themed post. The suggestion for this post came from Prof Ursula Martin of Oxford University, who told us about the ‘wood computer’.

It’s a Christmas tree! Image drawn and digitised by Jo Brodie.

The Wood Computer

by Jo Brodie, QMUL.

Other than asking someone “do you know what tree this is?” as you’re out enjoying a nice walk and coming across an unfamiliar tree, the way of working out what that tree is would usually involve some sort of key, with a set of questions that help you distinguish between the different possibilities. You can see an example of the sorts of features you might want to consider in the Woodland Trust’s page on “How to identify trees“.

Tree silhouettes image by Clker-Free-Vector-Images from Pixabay

Depending on the time of year you might consider its leaves – do they have stalks or not, do they sit opposite from each other on a twig or are they diagonally placed etc. You can work your way through leaf colour, shape, number of lobes on the leaf and also answer questions about the bark and other features of your tree. Eventually you narrow things down to a handful of possibilities.

What happens if the tree is cut up into timber and your job is to check if you’re buying the right wood for your project. If you’re not a botanist the job is a little harder and you’d need to consider things like the pattern of the grain, the hardness, the colour and any scent from the tree’s oils.

Wooden bridge image by Peter H from Pixabay

Historically, one way of working out which piece of timber was in front of you was to use a ‘wood computer’ or wood identification kit. This was prepared (programmed!) from a series of index cards with various wood features printed on all the cards – there might be over 60 different features.

Every card had the same set of features on it and a hole punched next to every feature. You can see an example of a ‘blank’ card below, which has a row of regularly placed holes around the edge. This one happens to be being used as a library card rather than a wood computer (though if we consider what books are made of…).

Image of an edge-notched card (actually being used as a library card though), from Wikipedia. Edge-notched Card (without the edges notched) by Daniel MacKay, image has been released into the public domain (CC0).

I bet you can imagine inserting a thin knitting needle into any of those holes and lifting that card up – in fact that’s exactly how you’d use the wood computer. In the tweet below you can see several cards that made up the wood computer.

One card was for one tree or type of wood and the programmer would add notch the hole next to features that particularly defined that type. For example you’d notch ‘has apples’ for the apple tree card but leave it as an intact hole on the pear tree card.  If a particular type of timber had fine grained wood they’d add the notch to the hole next to “fine-grained”. The cards were known, not too surprisingly, as edge-notched cards.

You can see what one looks like here with some notches cut into it. You might have spotted how knitting needles can help you in telling different woods apart.

Holes and notches

Edge-notched card overlaid on black background, with two rows of holes. On the top a hole in the first row is notched, on the right hand side two holes are notched. Image from Wikipedia. Randlochkarte mit zwei Schlitzungen (handgemalt) [Perforated card with two slots (hand-painted)] by Peter Frankfurt, image has been released into the public domain (CC0).

Each card would end up with a slightly different pattern of notched holes, and you’d end up with lots of cards that are slightly different from each other.

Example ‘wood computer’. At the end of your search (to find out which tree your piece of wood came from) you are left with two cards for fine-grained wood. If your sample has a strong scent then it’s likely it’s the tree in the card on the right (though you could arrive at the same conclusion by using the differences in colour too). The card at the top is the blank un-notched card.

How it works

Your wood computer is basically a stack of cards, all lined up and that knitting needle. You pick a feature that your tree or piece of wood has and put your needle through that hole, and lift. All of the cards that don’t have that feature notched will have an un-notched hole and will continue to hang from your knitting needle. All of the cards that contain wood that do have that feature have now been sorted from your pile of cards and are sitting on the table.

You can repeat the process several times to whittle (sorry!) your cards down by choosing a different feature to sort them on.

The advantage of the cards is that they are incredibly low tech, requiring no electricity or phone signal and they’re very easy to use without needing specialist botanical knowledge.

You can see a diagram of one on page 8 of the 20 page PDF “Indian Standard: Key for identification of commercial timbers”, from 1974.

The word ‘card’ features over 30 times on this page and the word Christmas over 10 times but this post isn’t actually about Christmas cards! We hope you had plenty of those 🙂 Merry Christmas.

Teachers: we have a classroom sorting activity that uses the same principles as the wood computer. Download our Punched Card Searching PDF from our activity page.

The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.

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CS4FN Advent 2023 – Day 24: Santa’s Sleigh – track its progress through the skies

We are nearly coming to the end of our CS4FN Christmas Computing Advent Calendar with one more post to come tomorrow. If you’ve missed any you can catch up by scrolling to the end and click on the Christmas Tree in the panel for the complete list so far.

Today’s advent calendar window shows Father Christmas’ sleigh with a sack full of presents ready for delivery. Today’s theme is about the many different online ways that you can now ‘track’ his movements around the world. You may be able to see (cloud permitting) his sleigh ‘in person’ as it flies over. In reality it’s International Space Station (ISS) whizzing past – but other interpretations are available 🙂

Visit this page https://www.astroviewer.net/iss/en/observation.php and type in your city to see when and where you might spot the ISS. On Christmas Day 2025 the ISS will pass over the South of England from around 6.17am to 6.22am, reaching its highest point at around 6.19am, so you’ll have to get up early!

You can track Father Christmas as he dashes through the sky, delivering presents. Image drawn and digitised by Jo Brodie.

1. NORAD Santa tracker

https://www.noradsanta.org/en/ for games
https://www.noradsanta.org/en/map (you can also track him on NORAD’s apps too)

Vintage photo image by Alexa from Pixabay

In 1955, so the story goes, an American department store published a newspaper advert with a phone number for children to call so that they could speak to Father Christmas. Unfortunately a misprint meant that the wrong number was given and instead people found they were talking to the US military’s Air Defense Command (now called North America Air Defense Command or NORAD).

Realising the mistake, but also spotting a great public relations opportunity, the team capitalised on this and began to make an annual event of it.

NORAD uses radar and geosynchronous* satellites to monitor Father Christmas. The satellites are able to detect infrared (heat) radiation and apparently Rudolph’s red nose gives quite a strong signal. This data is then shared with everyone via their website, though they don’t know in advance what route he’ll take.

If you’re visiting the website hover over the different bits of the picture as there are linked activities and extra information too.

*geo = Earth, synchronous = matching / following (like when you sync devices), the satellite follows the Earth’s orbit and is always above the same spot, so effectively (from the Earth’s point of view) the satellite appears not to move (it is moving but it follows the Earth’s rotation).

2. FlightRadar24 Santa tracker

https://www.flightradar24.com/R3DN053/335a9682

Father Christmas in flight image by Maria Guerrero from Pixabay

FlightRadar24 is a great website for telling you the answer to “what was that aircraft that’s just flown by?” It tracks the flight of aircraft all over the globe in real time, using a signal transmitted by the aircraft’s beacon (called a transponder) which announces where it is. Father Christmas’ sleigh has its own transponder too which is transmitting its location to receivers around the world.

An aircraft, or Santa’s sleigh, gets information about where it is from a GPS satellite (very similar to using a maps app on a smartphone and it telling you where you are and whether you should go left or right) and it then transmits this location info, along with other data, through its transponder.

There are thousands of receivers here on Earth, many of them in people’s homes and gardens (you can even apply to host a receiver antenna, or build your own with a Raspberry Pi) and whenever Santa’s sleigh passes over one of these ‘ground stations’ its signal is picked up and collected by FlightRadar24. The receivers are in different places so they are receiving the same signal at slightly different times and this information can be used to work out (by triangulation) how fast the sleigh is moving and in what direction.

Apparently Santa has been “able to extend the reach of his transponder by using the reindeer antlers as additional antenna” so the tracking should be fairly accurate.

3. Google Santa tracker

https://santatracker.google.com/

Google’s Santa Tracker has lots of games to play while you wait for Santa and his sleigh to take flight, including Code Boogie where you can try and program some dancing elves. You move little blocks (a bit like Scratch) to copy the dance moves and, if you get it right, it will show you the underlying JavaScript code.

Dave Holmes, a developer who works at Google and who works on the Santa Tracker project says “Santa Tracker launched in 2004, and has been an important project at Google ever since. While there’s a small core team dedicated to Santa, up to 20 or so Googlers volunteer to help make it happen every year, and it’s become a true community effort. It’s also a way for our developers to try things and see what Google products can do … I like to say that everything I’ve learned at Google, I learned from Santa.”

Google has also added some ‘Easter eggs‘ to its search page – try typing in Christmas or where is Santa to https://www.google.com/. You can also colour in some images online at their Christmas-themed Art Coloring Book, from Google’s Arts and Culture.

Further reading

The Googlers who help track Santa each Christmas (22 December 2021) Google Blog

4. Early internet Santa-themed humour

Image by Jo Brodie for CS4FN.

Back in the early 1990s email was very new but right from the start people used it to send each other amusing things. One of them was a rather literal consideration of the physics of a sleigh that is laden with gifts and a traditionally overweight Santa, led by a team of reindeer moving at unlikely speeds (after all Father Christmas has to get around the entire world to deliver presents, in just one day). The author (unknown) began –

“No known species of reindeer can fly. BUT there are 300,000 species of living organisms yet to be classified, and while most of these are insects and germs, this does not COMPLETELY rule out flying reindeer which only Santa has ever seen.”

But then goes on to point out that such a gift-delivery system would be working far beyond normal levels and would probably end in disaster, suggesting that –

“In short, they will burst into flame almost instantaneously, exposing the reindeer behind them, and create deafening sonic booms in their wake. The entire reindeer team will be vaporized within 4.26 thousandths of a second. Santa, meanwhile, will be subjected to centrifugal forces 17,500.06 times greater than gravity. A 250-pound Santa (which seems ludicrously slim) would be pinned to the back of his sleigh by 4,315,015 pounds of force.”

Fortunately Father Christmas has his own magic, meaning that we don’t need to worry too much about him disobeying the laws of physics. But he and his reindeer really deserve those cookies, milk and carrots!

You can read the full post here: The Physics of Santa and His Reindeer Snopes.com

The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.

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CS4FN Advent 2023 – Day 23: Bonus material – see “Santa’s sleigh” flying overhead

This short post, part of our CS4FN Christmas Computing Advent Calendar, is to let you know that you may be able to watch Santa’s sleigh as it goes overhead on Christmas Day (or Christmas Eve). It doesn’t matter if you believe in Father Christmas or not, whether you’ll actually see his sleigh really only depends on how cloudy it is! In fact Santa’s sleigh follows the orbit of the International Space Station (ISS) remarkably closely…

Santa’s sleigh: Father Christmas will soon be tethering the sack of gifts to the sleigh with very strong straps (not shown) because he’ll be flying very fast and very high.  

In the unlikely event that any small children are awake unusually early on Christmas Day and it’s not cloudy then you might be able to catch a bright light passing overhead at around 05:54 in the morning as Father Christmas zips around the world delivering presents at incredible speeds.

The timings below are for London, UK but you can enter your own city and see if Father Christmas will be passing near you, and when.

DayDateTimeVisibleMax HeightAppearsDisappears
Sun24 Dec6:40 am6 min86°21° above W10° above E
Mon25 Dec5:54 am4 min88°82° above WSW10° above E

See ‘How to spot the station‘ and find out what ‘max height’ and ‘appears’ means in context. You can also use NASA’s Spot The Station app for phones.

Other ways to track Santa – NORAD, FlightRadar24 and Google’s Santa Tracker.

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CS4FN Advent 2023 – Day 23: Father Christmas – checking his list, spotting the errors

Our CS4FN Christmas Computing Advent Calendar has now been running for 23 days! That’s one post every single day, matching a computing-themed blog post to the image on the front of the advent calendar. If you’d like to see how well we’ve managed this please scroll to the end where you can find all of our previous Advent Calendar posts.

Today’s picture is of Father Christmas who, we’ll assume, is re-checking his list and packing his sleigh ready for a long flight around the world, where he’ll be ‘accepting cookies’ as he goes.

Father Christmas, about to do his pre-flight checks (twice). Image drawn and digitised by Jo Brodie.

As the song implies, he takes particular care over his list checking it twice to make sure there are no mistakes. In that respect he’s a little like computer scientists who put systems in place to make sure that when they send data to someone else that person can tell quickly if it’s arrived correctly. Today’s post is about reducing errors (and trying to avoid introducing errors). (We don’t know what data collection methods Father Christmas used though.)

1. Reducing errors: check digits

Once I’d reached the age of about 12 my parents started to let me go by myself to my friend’s house which was about a 15 minute walk away. When I arrived I would use my friend’s parents’ landline phone (with permission) to “give 3 rings” to my parents. This meant that I rang my parents’ number – but they didn’t answer, instead they let the phone ring three times and then I hung up. That way they knew the call was from me (our pre-agreed code) but no-one was charged to make or receive a call and they knew I’d arrived safely. (Obviously if the phone rang for longer they’d know it was probably from someone else and answer it).

Computer scientists also use an agreed code when sending data to another person or computer over a network – they want to make sure their data arrived safely too. Data is* sent as binary 1s and 0s and sometimes there’s a scrambling error in the transmission resulting in a 1 arriving as a 0, or a 0 arriving as a 1. A neat way to find out if this might have happened is to double-check what it was supposed to be, by using something called a parity bit (parity means ‘equal’) or check digit. This digit is added to each block of data you’re sending and computer scientists came up with this to let you check if the arriving data looks correct.

Here’s how it works

Suppose you want to send a message consisting of the numbers 6, 13, 2 and 12. These numbers can be converted into binary for data transmission: for example 6 in binary is 0110, 13 is 1101, 2 is 0010 and 12 is 1100. In the 5-row table below these are written in black (the top line is 6 and the fourth row is 12 – we’ll come to the red numbers in a moment).

We’ll now add a parity bit to each row, according to a rule, to make them five digits long.

The rule is that if the binary number has an odd number of 0s we even it up by adding another 0. If there’s an even number of 0s we just add a 1.

In the 1st row 0110 has an even number of zeroes so a 1 is added, 1101 has an odd number of zeroes so an extra 0 is added. Once we’ve checked all four rows we end up with a new parity column (shown in red on the right to make it stand out) on the right. We can also add a new parity row at the bottom as well, by doing the same thing for each of the numbers but read as a column. The first column has an even number of zeroes so we add a 1, the next just has one odd zero so we add a 0 there and so on.

We’ve added extra data to be sent, but this redundancy check (the extra info isn’t part of the message itself but helps support it) makes it easier for the person receiving the information to know if it’s OK or where any problem is.

01101
11010
00100
11001
10101

Let’s pretend you’ve just pressed send and your 1s and 0s are winging their way to your friend.

Binary image by Gerd Altmann from Pixabay

Unfortunately there was a small error in transmission and one of the numbers has ‘flipped’. Will your friend be able to tell which one it is? (Remember they don’t know what your message was supposed to say, they can only see what’s arrived).

Here’s the (slightly scrambled) data that they receive.

01101
10010
00100
11001
10101

They can use the parity bit information to check each row and column. The first row looks fine – two zeroes (even) and the parity bit one says 1 so that’s right. The second row looks wrong though – there’s an even number of zeroes so you’d expect a 1 in the parity bit – but it says 0, so you know there’s a mistake somewhere in row 2, but your friend won’t know where yet. They need to check the columns too.

Column 1 looks good, there are two zeroes and the parity bit says 1 so that’s correct. Column 2 has an even number of zeroes so you’d expect the parity bit to be 1, but it’s 0. So we know the problem is in Row 2 and Column 2. If we look at where they intersect we can see that a 1 has flipped to a 0, shown below in bold and blue. Your friend can correct the data and translate the binary back into the original numbers.

01101
10010
00100
11001
10101

You could try this with a friend or family member. Think up any 4 numbers between 0 (binary 0000) and 15 (binary 1111) then transmit your binary code with one error and see if they can work out which data bit flipped. Or… you can do it as a magic trick with a pack of cards (see the activity at the end).

*are, for the pedants 🙂

Further reading

Writing together: Clarence ‘Skip’ Ellis – about Clarence Ellis who used his knowledge of computing to bypass parity checks. The company he worked for was running out of punched cards (we’ll look at these in more depth later in the week) which the company’s computer used to store data. He was able to find a way for his colleagues to re-use the cards they already had, without triggering parity check problems – in doing so the payroll program could be run and everyone could get paid.

Handy binary cheat sheet. (Repeated after the dividing black line to show how the binary number is formed). Image created by Jo Brodie.

2. Trying not to introduce errors: when spellcheck goes worng

Another thing Father Christmas needs to do is check that he has the correct names of all the good children he’ll be giving presents to. He might use a spellchecker for this – this is something that reads the words in a document and compares them to a pre-set list. If a word is spelled in an unusual way the computer will alert you and ask if you want to change it to the one in the list or if you want to add it as a new spelling to the list. It would spot that I spelled ‘wrong’ wrongly in the heading for this section and ask if I meant ‘wrong’ instead of ‘worng’.

Find and replace

Sometimes people want to change a word in their document that appears many times. For example you might put TBA (which can mean ‘to be agreed’ or ‘to be arranged’) as a temporary placemarker in a Microsoft Word document and later decide that every time the document says ‘TBA’ you’d prefer it to say “to be determined” instead. You don’t have to manually delete and retype every single instance of ‘TBA’, you can ‘automate’ the process using the Find and Replace option. Word will then find every ‘TBA’ automatically and change it to ‘to be determined’.

Sometimes this doesn’t go quite as expected.

In the UK the word ‘ass’ usually means donkey but in the US it’s a slightly less polite word for bottom. A slightly more polite word might be ‘butt’ so you – being polite – want to make sure that any time the word ‘ass’ appears in a particular document it’s replaced with the word ‘butt’. This is unfortunate though if you happen to be the editor of a book about donkeys, which is now suddenly about bottoms.

Not donkeys’ bottoms, but zebras‘ – image by chezbeate from Pixabay

It’s much worse if your document talks about your class at school (clbutt?). Or perhaps it’s some homework about the assassination of an American president (buttbuttination?). Or maybe you need a new password (pbuttword), or even a new passport (pbuttport). Your document is now absolute gibberish and you would not pbutt any exams with that. Where’s spellcheck when you need it?

These types of mistakes are not that uncommon, I’ve even done it myself with the addresses of schools where I send copies of our CS4FN magazine to teachers.

I had a column in my address database which said things like UK, U.K. or United Kingdom and I decided I wanted them all to match and say “United Kingdom”. So… I used find and replace and asked my computer to turn every mention of ‘UK’ or ‘U.K.’ into United Kingdom. It worked beautifully… but I didn’t check the other columns.

I discovered my mistake when ‘Luke’ at a school on ‘Duke Road’ didn’t get his copy of the magazine and it was returned to me by the Post Office as the address was unreadable. I then had to correct both LUnited Kingdome‘s name and his DUnited Kingdome Road address 😉 Oops.

Here are some other examples

and below is a reply to the post above showing what happened when someone changed TBA to ‘to be determined’ without noticing that the string of letters also appears in the word basketball.

3. Magic trick activity: parity check with playing cards

Playing cards by Dmitry Fomin, via Wikipedia (cards’ images released into the public domain, CC0). Back of playing card image by Michael Schwarzenberger from Pixabay. Composite created by Jo Brodie for CS4FN.

You could demonstrate the parity checking (that we did above with 1s and 0s) as a card trick – you just need an assistant and an audience. If you look closely at the pattern of cards in the picture above, and the pattern of 1s and 0s further up in this post you might notice a similarity…

Give a pack of shuffled cards to an audience member and ask them to deal out 16 cards in four rows either face up or face down (their choice). An example is shown in the left of the picture above. Tell them that in a moment you’re going to ask them to turn over a card while you’re not looking and later, you’ll tell them which card they flipped over. Announce that your assistant is going to make it ‘even harder’ by adding an extra column and row (I bet you can see where this is going). Of course, your assistant is adding a parity bit to the rows and columns (but your audience doesn’t know that) – an example is shown in the middle picture above.

Now avert your eyes (or get someone to blindfold you) and ask the audience member to turn over one card from the grid without telling you which. (Example in the picture on the right, above).

When you look at the grid you can quickly work out which one has been turned over, using exactly the same method we used with the 1s and 0s above.

This trick is a variation of one invented by New Zealand computer scientist, Tim Bell, and you can find more information about it and detailed instructions (as well as ideas to make it seem like you’re really a magician) in our free booklet called The Magic of Computer Science: card tricks special. The trick is called ‘The Out of Body Experience‘ and you can find it on pages 24-31 (pages 13 – 16 of the 33 page PDF).

The Magic of Computer Science 1

The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.

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EPSRC supports this blog through research grant EP/W033615/1.

CS4FN Advent 2023 – Day 22: wreaths and rope memory – weave your own space age computer

Each day throughout December (until Christmas Day) we’ll be publishing a computing-themed blog post suggested by the picture on the front of our Advent Calendar. Today’s image on the door of the CS4FN Christmas Computing Advent Calendar is a Christmas wreath which made me think of wires and of weaving.

A Christmas wreath. Image drawn and digitised by Jo Brodie.

You might remember that our first advent calendar post was about the links between coding and knitting. Today’s post looks at an even more literal version of that: core rope memory.

1. Core rope memory: the Apollo space mission’s woven computer memory

by Jo Brodie, QMUL.

Firstly it looks like this.

Rope memory from the Apollo Guidance Computer. Image by NASA from Wikipedia, in the Public Domain.

Secondly it got us to the Moon!

Probably the world’s first portable computer

Core rope memory was made up of small ‘eyelets’ or beads of metal called ferrite that can be magnetised (these ring-shaped magnets were known as cores) and copper wire which was woven through some of the eyelets but not others. An electrical current passing through the wires made the whole thing work. A wire that passed through an eyelet would be read as a binary 1 when the current was on but if it passed around one then it would be read as 0. This meant that a computer program, made up of sequences of 1s and 0s, could be permanently stored by the pattern that was woven. This formed the ‘fixed’ read-only memory in the Apollo guidance computer system; a different configuration (using smaller cores) made up its erasable magnetic-core memory.

This type of memory was woven in the 1960s for NASA’s Apollo moon mission by women who were skilled textile workers. They would work in pairs and use a special hollow needle to thread the copper wire through one magnetic core and then the other person would thread it back through a different one, following instructions from another program which indicated which of the eyelets to use.

That program was first developed on a computer (the sort that took up a whole room back then) and then translated into instructions for a machine which helped the weavers get the wire threads into the correct position. It was very difficult to undo a mistake so a great deal of care was taken to get things right the first time, especially as it could take up to two months to complete one block of memory. Some of the rope weavers were overseen by Margaret Hamilton, one of the women who developed the software used on board the spacecraft.

Margaret Hamilton standing next to listings of the software that she and her MIT team produced for the Apollo Project. Image from Wikipedia (in the public domain).

Several of these pre-programmed core rope memory units were combined and installed in the guidance computers of the Apollo mission spacecraft, to fly astronauts safely to the Moon and back.

NASA needed on-board guidance systems to control the spacecraft independently of Mission Control back on Earth. They needed something that didn’t take up too much room or weigh too much, that could survive the shaking and juddering of take-off and background radiation – core rope memory fitted the bill perfectly.

It packed a lot* of information into a small space and was very robust as it could only break if a wire came loose or one of the ferrite eyelets was damaged (which didn’t happen). To make sure though, the guidance computer’s electronics were protected by being sealed from the atmosphere. They survived and worked well, guiding the Landing Modules safely onto the Moon.

*well, not by modern standards! The guidance computer contained only around 70 kilobytes of read only memory.

2. A brief history of the digital revolution, part 1: from birth to the moon

by Lewis Dartnell. This post is from 2008.

The Royal Institution Christmas Lectures 2008 invited you on a high tech trek to build the ultimate computer. The Christmas Lectures talk a lot about the current cutting-edge of computer technology, but what were things like in the early days of the digital revolution? The researcher for the 2008 Christmas Lectures, Lewis Dartnell, takes us through the story.

Electronic computers have come a long way since their birth only 50 years ago. One of the very first digital computers was built at the University of Manchester, a prototype called Manchester Mark I. The machine was revolutionary, with its complex processing circuits and storage memory to hold both the program being run and the data it was working on. The Mark I was first run on 21 June 1948 and paved the way as a universal computer that is truly versatile and can be reprogrammed at will, rather than being hard-wired for a single particular task.

A vacuum-tube (specifically a voltage-regulator tube) in use. Image by VA7IS from Wikipedia (released into the public domain).

These earliest computers used technology called vacuum tubes, which were essentially just like filament light bulbs. Because they get so hot, such vacuum tubes were really power hungry and not very reliable. Typically, computers like the Manchester Mark I, processing using vacuum tubes, could only be run for a few hours at a time before one of the vacuum tubes broke and had to be replaced. The biggest break-through in modern computing came with the invention of the transistor, a small electronic component that can perform the same function as a vacuum tube, but is much more energy efficient and reliable. The beauty of the transistor is that computer scientists found ways of making them smaller and smaller, and to connect a number of them together into a single miniaturized processing board called an integrated circuit. These came to be known as microchips, and form the basis of all the computers made today.

A major drive for the development of microchip technology was the Apollo programme, begun in 1961 to land humans on the Moon. Although the vast majority of the complex calculations to do with plotting the trajectory and navigating to the moon were performed by enormous banks of computers back on Earth, it was crucial for the spacecraft to have their own on-board computer system. This was called the Apollo Guidance Computer (AGC), and both the command module and the lunar module, which actually made the descent to the surface of the moon, had one each. These ground-breaking computers provided the astronauts with crucial flight information, helped them make course corrections and to touch-down gently on the moon’s surface. Because it’s absolutely crucial to reduce the amount of mass and power usage on a spacecraft as far as possible, developing these guidance computers really pushed the technology in miniaturising integrated circuits.

The Display and Keyboard Interface (known as DSKY and pronounced Disky) of the Apollo mission’s guidance computer. Image by
Brandrodungswanderfeldhackbau from Wikipedia (released into the public domain).

The Apollo Guidance Computer not only helped drive the early development of microchips, but it also suffered one of the most infamous computer crashes in history. During the descent down to the Moon’s surface the AGC started displaying two error messages that the two astronauts, Neil Armstrong and Buzz Aldrin, weren’t familiar with. Engineers back at mission control on Earth quickly tried to identify the error code, and what it might mean for the lunar landing. Something that had never happened in any of the training simulations was now overloading the flow of data into the computer, the first time it had ever been used for real. Time was running out with only a limited amount of rocket fuel on-board and the Moon rushing up towards them. Luckily the computer entered a fail-safe mode, aborting low-priority calculations but able to continue with the critical tasks for the landing.

It wasn’t until the investigation afterwards that it was realized just how lucky Neil Armstrong and Buzz Aldrin had really been. The root of the problem was that the real attempt at the Moon landing was the first time an important radar system had been plugged into the computer, sending data into the AGC that wasn’t needed for the landing. This almost totally overloaded the computer, but by amazing luck, the amount of spare processing power built into the system for safety was almost exactly the amount being wasted by the un-needed radar, and the AGC didn’t crash completely.

3. Activity 1 – make your own core rope memory

A nice craft activity is to create a cut-down version with beads and coloured threads. You string 8 beads (with a gap between them) on one thread to form a single ‘byte’ (of 8 binary bits). Then think of a short word or name. Using one piece of thread for each letter (easier to see if threads are coloured but not essential) you can weave it through or around each bead according to the binary code for each letter. If the thread goes through the bead that’s a 1, around the bead is 0.

To make the capital letter A (01000001, according to the conversion from binary to letters table) you’d go around the first bead, through the second, then around all the other beads until going through the eighth bead.

My name’s JO so mine would have only three threads (one to hold the 8 beads and two to spell my name). One of my threads would go around, through, around, around, through, around, through, around to ‘spell’ the capital letter J (01001010). Let’s hope you have a slightly longer name!

4. Activity 2 – create an origami laurel wreath

Not only do we have a wreath-themed activity in our back catalogue (!) but in a delightful coincidence this story also relates to Apollo (the Greek god). If you’re wondering what origami might have to do with computing it’s just another way of looking at algorithms and instructions. Also, decomposition (breaking a problem into smaller parts) because you can re-use the instructions needed for the laurel wreath to make other origami items. We like using ‘unplugged’ activities like this to demonstrate computing concepts.

Wreath instructions here.

Create an origami laurel wreath from nested triangles of paper. Image by Paul Curzon / CS4FN.

The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.

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EPSRC supports this blog through research grant EP/W033615/1.

CS4FN Advent 2023 – Day 21: stars and celestial navigation

Every day from the 1st to the 25th of December this blog is publishing a Christmas Computing post, as part of our CS4FN Christmas Computing Advent Calendar. On the front of the calendar for each day is a festive cartoon which suggests the post’s theme – today’s is a star, so today’s post is about finding your way: navigation.

Follow that star… Image drawn and digitised by Jo Brodie.

In modern cities looking up at the night sky is perhaps not as dramatic as it might have been in the past, or in a place with less light pollution. For centuries people have used stars and the patterns they form to help them find their way.

GPS Orbital Navigator Satellite (DRAGONSat), photograph by NASA. Image not in copyright and used for non-commercial purposes.

There are many ways our explorations of space have led to new technologies, though satellites have perhaps had the most obvious effect on our daily lives. Early uses were just for communication, allowing live news reports from the other side of the world, with networks that span the globe. More recently GPS – the Global Positioning System has led to new applications and now we generally just use our phones or satnav to point us in the right direction.

The very first computers

by Paul Curzon, QMUL.

Victorian engineer Charles Babbage designed, though never built the first mechanical computer. The first computers had actually existed for a long time before he had his idea, though. The British superiority at sea and ultimately the Empire was already dependent on them. They were used to calculate books of numbers that British sailors relied on to navigate the globe. The original meaning of the word computer was actually a person who did these calculations. The first computers were humans.

An American almanac from 1816. Image by Dave Esons from Pixabay

Babbage became interested in the idea of creating a mechanical computer in part because of computing work he did himself, calculating accurate versions of numbers needed for a special book: ‘The Nautical Almanac’. It was a book of astronomical tables, the result of an idea of Astronomer Royal, Nevil Maskelyne. It was the earliest way ships had to reliably work out their longitudinal (i.e., east-west) position at sea. Without them, to cross the Atlantic, you just set off and kept going until you hit land, just as Columbus did. The Nautical Almanac gave a way to work out how far west you were all the time.

Maskelyne’s idea was based on the fact that the angle from the moon’ to a person on the Earth and back to a star was the same at the same time wherever that person was looking from (as long as they could see both the star and moon at once). This angle was called the lunar distance.

The lunar distance could be used to work out where you were because as time passed its value changed but in a predictable way based on Newton’s Laws of motion applied to the planets. For a given place, Greenwich say, you could calculate what that lunar distance would be for different stars at any time in the future. This is essentially what the Almanac recorded.

Moon image by PollyDot from Pixabay

Now the time changes as you move East or West: Dawn gradually arrives later the further west you go, for example, as the Earth rotates the sun comes into view at different times round the planet). That is why we have different time zones. The time in the USA is hours behind that in Britain which itself is behind that in China. Now suppose you know your local time, which you can check regularly from the position of the sun or moon, and you know the lunar distance. You can look up in the Almanac the time in Greenwich that the lunar distance occurs and that gives you the current time in Greenwich. The greater the difference that time is to your local time, the further West (or East) you are. It is because Greenwich was used as the fixed point for working the lunar distances out, that we now use Greenwich Mean Time as UK time. The time in Greenwich was the one that mattered!

This was all wonderful. Sailors just had to take astronomical readings, do some fairly simple calculations and a look up in the Almanac to work out where they were. However, there was a big snag. it relied on all those numbers in the tables having been accurately calculated in advance. That took some serious computing power. Maskelyne therefore employed teams of human ‘computers’ across the country, paying them to do the calculations for him. These men and women were the first industrial computers.

Book of logarithms, image by sandid from Pixabay

Before pocket calculators were invented in the 1970s the easiest way to do calculations whether big multiplication, division, powers or square roots was to use logarithms (not to be confused with algorithm). The logarithm of a number is just the number of times you can divide it by 10 before you get to 1. Complicated calculations can be turned in to simple ones using logarithms. Therefore the equivalent of the pocket calculator was a book containing a table of logarithms. Log tables were the basis of all other calculations including maritime ones. Babbage himself became a human computer, doing calculations for the Nautical Almanac. He calculated the most accurate book of log tables then available for the British Admiralty.

The mechanical computer came about because Babbage was also interested in finding the most profitable ways to mechanise work in factories. He realised a machine could do more than weave cloth but might also do calculations. More to the point such a machine would be able to do them with a guaranteed accuracy, unlike people. He therefore spent his life designing and then trying to build such a machine. It was a revolutionary idea and while his design worked, the level of precision engineering needed was beyond what could be done. It was another hundred years before the first electronic computer was invented – again to replace human computers working in the national interest…but this time at Bletchley Park doing the calculations needed to crack the German military codes and so win the World War II.

The creation of this post was funded by UKRI, through grant EP/K040251/2 held by Professor Ursula Martin, and forms part of a broader project on the development and impact of computing.

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Click the tree to visit our CS4FN Christmas Computing Advent Calendar

EPSRC supports this blog through research grant EP/W033615/1.