Archive for the ‘Computing’ Category

Monthly Excel planner

Monday, December 19th, 2011

I’ve previously produced a weekly planner Excel spreadsheet, but recently I’ve needed to use a monthly planner with hourly time slots.

It is a simple one page monthly planner. The times from 6am-1am are along the top, and the days of the month from 1-31 are down the side. For the months with 28, 29, or 30 days long you can just cross out or delete the extra days. If you need a different time range it is very easy to edit as well.

monthly excel planner

You can either use this on screen, or print it out. With Microsoft Excel there is an easy option to specify that you want the planner to fit on a single A4 sheet of paper. In the ‘Page Setup’ window set the orientation to Landscape and tell it to fit to 1 page wide by 1 page tall. Here is the free download link:

Download monthly Excel planner – 9kB zipped

I’ve saved this as a Microsoft Excel 97 XLS file so it should work in all old or new version of Microsoft Excel or OpenOffice.

2013 Staff holiday planner spreadsheet

Friday, November 18th, 2011

At the time of writing it nearing the end of 2011 so some of you may be searching for my previous staff holiday planner for 2012. If you are planning very far ahead (or if you are reading this in 2012/2013) you might want my 2013 staff planner. This is my latest free spreadsheet that can help you track staff holidays, training, sick days and offsite days.

2013 staff holiday planner spreadsheet

It comes configured with formulas that can automatically track the total number of holiday days remaining (columns C&D) for each employee. If you don’t want to use this simply delete those columns.

The default formula subtracts 1 or 0.5 from the remaining holiday if the employee cells contain the words ‘holiday’ or ‘half. You can copy and paste (ctrl-c, ctrl-v) the coloured tags (holiday, half, training, etc) from the top left into the staff planning cells and the totals are automatically updated.

It is easy to customise the formulas if you want to factor in sick days for example. See the 2012 planner for more example formulas. Note that the 2013 calendar formulas count the entire row (which includes the last bit of 2012 and the first bit of 2014), whereas the 2012 calendar formulas just count the 2012 year. You can adjust the formulas to suit your requirements.

As always the week numbers are based on ISO 8601, and the top and left parts of the staff planner are frozen so you can always see them – this makes navigation easy. Here is the download link:

Download 2013 staff holiday planner spreadsheet – 23kb

As the staff holiday planner has over 365 columns you won’t see the whole year if you open it with an ancient spreadsheet package such as Excel 97. You’ll need to use a more modern spreadsheet package such as Excel 2007 or OpenOffice (which is free). One workaround if you are forced to use Excel 97 at work is for you to use OpenOffice at home to split the spreadsheet into 2, one part for 2013 H1, and one for 2013 H2.

How to edit PDF files for free

Wednesday, August 31st, 2011

I had a PDF form which I needed to fill in. The form was not editable, but I still wanted some way to fill in the fields on the computer rather than having to print it out and fill it in by hand.

A quick search shows that there are many other people wanting to do the same thing, but there aren’t many solutions that actually work. Many of the suggestions/solutions that I found online didn’t work at all. These were my requirements:

  • Add text to an existing uneditable PDF.
  • Save the PDF with the new text in place.
  • Ability to re-open the PDF and continue editing the newly added text.
  • I wasn’t interested in the ability to edit the PDF form itself – only the new text that I added.
  • The software should be free.
  • I didn’t want software with a time limited trial.
  • The software had to leave no watermarks on the PDF.
  • I wanted PC based software rather than web based – I don’t want to have to submit my PDFs to some company that I may never have heard of.

The software that I found that allowed me to fill in my PDF forms as per my requirements was called PDF-XChange Viewer.

How to install the PDF editing software

The easiest way to install PDF-XChange Viewer is to download the EXE installer from their webpage. You should be careful when installing, as by default it will change some of your computer’s settings and try to install a browser toolbar.

On the ‘Select Components’ screen I deselected everything except for the help file. I don’t want any extra menus added to Windows Explorer, browser extensions, or automatic update checking. This is a tool that I’m only going to use occasionally so I want it be unobtrusive when not in use.

pdf editor install 1

Then on the ‘Select Additional Tasks’ screen I made sure that the ‘Set PDF-XChange Viewer as default viewer for PDF files’ was unticked. I want to continue to use Adobe Reader for viewing PDFs.

pdf editor install 2

On the ‘Install the Tracker Ask Toolbar’ screen I unticked the top option. It would be easy to misread it if you are quickly clicking through the install, and think that this option is just to agree to the main licence terms. But read carefully and you’ll see that it is for agreeing to the licence terms for the Ask Toolbar and confirming that you want to install it. So untick it unless you want the Ask Toolbar.

pdf editor install 3

Finally when I started the tool for the first time I told it not to make PDF-XChange Viewer the default PDF viewer, and set the option for it not to ask me again.

How to add text to your PDFs

After carefully completing the install this is how to add text to your existing PDFs. I’m using a random uneditable PDF that I found on the internet.

First load the PDF into PDF-XChange Viewer. You should be able to figure out how to do that yourself!

The easiest way to write on the PDF is with the ‘Typewriter Tool. Go to Tools->Comment and Markup Tools->Typewriter Tool->Default Style to select it.

pdf editor typewriter tool

Then you can simply click anywhere on the document and start typing. You’ll see the Typewriter Tool cursor where the text will appear.

editing a pdf

To test that your changes get saved properly: save a copy of the PDF and then load it into Adobe Reader.

To test that you can re-edit your text additions: load the PDF back into PDF-XChange Viewer and try re-editing your text. You can double-click on your text to get the editing cursor back. And you can right click on any of your new text boxes to get the option to delete them.

2012 Excel week numbers calendar

Wednesday, June 15th, 2011

We are nearly half way through 2011 so you might have already started planning for 2012. This easy to read one page Excel calendar has the whole of 2012 on one page, with a good sized box for each day of the week – each day has five free cells for your use.

It has the week numbers down the side – the week numbers are written according to ISO 8601. If you work in a company and your projects are planned in terms of week numbers it can be very useful to have a calendar which lists them.

2012 excel week numbers calendar

I’ve frozen the days of the week lables at the top so they are always visible, and the months are alternately coloured to make it easy to see which month you are on.

There are two versions of this spreadsheet, one saved using the newer XLSX format, and one using the older Excel 97 compatible XLS format. Both file types can also be loaded in the free OpenOffice Calc spreadsheet if you don’t have Microsoft Excel.

2012 week numbers calendar (Excel 2007+ or OpenOffice)
2012 week numbers calendar (Excel 97+ or OpenOffice)

I also have a one page calendar for 2012, and a staff holiday planner for 2012 if you are looking for a slightly different calendar.

Amazon CloudFront and S3 maximum cost

Thursday, May 19th, 2011

When using utility computing platforms such as Amazon CloudFront, S3, EC2, or similar platforms from other companies, you are charged according to how much usage you or other people make of the files and services you publicly expose.

If you configure your files or services to be private only to you then you can easily control the cost. But when you make them accessible to the public (e.g. by hosting your website images on CloudFront) your costs are determined by people you have never met.

The costs tend to work out pretty cheap under normal usage, and these utility computing platforms are a great idea in theory. But what if the usage isn’t normal? What if someone decides to launch a DDOS attack on you by downloading huge amounts of data from your CloudFront or S3 account for example? I’ve no doubt that Amazon could handle the load, but could your bank account, or business cope?

cloud maximum cost worst case scenario

I’m not singling out Amazon here; the same applies for any ‘pay for computing power / bandwidth’ service. It is just that Amazon’s services set the benchmark for other similar companies so their platform provides a good example to base my calculations on.

The chances of such an attack happening to you are probably small, but the impact could be large, so it is worth doing the calculations before signing up.

Calculating the Amazon CloudFront worst case scenario

In order to calculate the worst case scenario we first need to understand how the pricing works. Amazon provides a page of pricing information on their website. You are charged for both bandwidth used, and the number of HTTP requests. The bandwidth cost varies depending on where in the world the data is downloaded from.

There are also some minor costs for file storage if you use S3 to store your data, and for loading the data if you use a custom origin server – but these are likely to be very minor costs so I will only use the bandwidth and number of requests for my calculations.

Next we need to know the maximum amount of bandwidth and requests that can be be used with your default account. Although it isn’t very easy to spot, there is a default limit listed on that pricing page of 1000 requests per second and 1000 megabits (megabits not megabytes – 1000 megabits = 125 megabytes) per second. That is a lot of data for any small hobby or business site but Amazon can cope with it. They even provide a request form if you need a higher limit.

Using these values you can see that in an hour the maximum number of requests is 3,600,000 and the maximum bandwidth usage is about 450 gigabytes.

The most expensive region to download data from is Japan so I will base my calculation on the data being downloaded at the maximum number of requests and bandwidth from the Japan prices (starting at $0.201/GB and $0.0095 per 10,000 requests as of May 2011). Of course in reality it would be impossible for someone to hit you with the maximum load, but that doesn’t matter – I’m calculating the theoretical worst case scenario here.

As the bandwidth pricing is tiered (as you move up the usage tiers the cost goes down) it is a bit hard to calculate the cost using a calculator. Amazon does provide its own cost calculator but I didn’t fancy using it for each data point so I’m using Excel instead. I’m using their cost calculator only to cross check my values to make sure that they are correct to an acceptable margin of error.

If you ever want to calculate tiered pricing then the SUMPRODUCT function in Excel is what will make it easy (once you figure out its cryptic syntax that is).

CloudFront worst case hour by hour cost for the first day

The first graph shows the theoretical worst case scenario cost for the first 24 hours of this imagionary DDOS attack on your account.

amazon cloudfront maximum cost per hour

After the first hour 0.45TB and 3,600,000 requests could have been charged to your account at a cost of nearly $94. By the end of the day the cost is just over $2200.

If an attack like this started how long would it take you to notice? Unless you sign up to a 3rd party monitoring service you wouldn’t find out about the problem until you next signed into the Amazon Web Services (AWS) console.

Even if you try to check everyday you can be hit with a big cost while you are asleep, on a plane, at dinner, or with friends. For a big business $2200 might be nothing, but how many hobbies website builders who are using AWS could say the same?

CloudFront worst case day by day cost for the first month

The next graph shows the maximum cost over 30 days. The subtle curve is the effect of the tiered pricing kicking in reducing the bandwidth cost each time you pass the next tier.

amazon cloudfront maximum cost per day

After a week your cost is over $11,000, at two weeks it is nearly $22,000, and after 30 days it could be over $42,000. About $40,000 of that is the bandwidth cost and only $2,000 is the requests cost. At the end of 30 days a maximum of 324TB of data could have been downloaded (theoretically).

Would Amazon spot and stop the bandwidth usage?

If this happened to you would Amazon (or similar companies) warn you?

I can’t find anything in their information that suggests they would. I’m not even sure if they’d notice. Although the bandwidth usage and number of hits might be huge for you, it’s peanuts for Amazon. Remember I’m basing these figures on their default throttled account. You can request much higher usage limits if you want.

Would you get a refund if this happened? Again I don’t know as their information mentions nothing about this. It does say that use are you are soely responsible for the use of your content, which may mean that if it is misued (e.g. DDOS attack) it is your responsibility to pay. You can understand that from Amazon’s point of view they will still incur costs for their own bandwidth whether the bandwidth usage is beneficial to you or not.

It would be good to see Amazon (and similar companies) clarifying their policies about whether they will offer any assistance in the event of an attack.

What do people pay for normal CloudFront / S3 usage?

There are many people posting about their AWS bills. Most of the stories I’ve read are about people saying how small their bill is. Here is a list of accounts I’ve found, some are using CloudFront, and some S3 (prices are mostly per month).

$0.12 – for a couple of days usage.
$0.86 – to host static files for a month.
$1.00 – a month to host static files.
$1.00 – a month at most for website data.
$1.22 – in a month for website images.
$1.30 – to make site go faster .
$1.50 – to host nutritional leaflet each month.
$1.69 – for a months image hosting to make site faster.
$1.81 – to serve blog images for a month.
$2.00 – for image hosting a month.
$5.00 – to make large site faster with CloudFront.
$5.00 – a month to make site ‘Reddit/Digg proof’.
$70.00 – a month on S3/CloudFront worked out cheaper than their dedicated server.
$440.40 – for storing images produced by a MySpace application.
$500,000 – a year saved by SmugMug by using S3.

Has this problem been mentioned before?

This problem has been mentioned many times on Amazon’s Web Services forums, so Amazon are aware of the issue, but as far as I’m aware no one has ever (until now!) produced worst case data for excessive usage.

Taking this thread as an example.

  • 2006 5th May – Someone requests feature to limit cost / bandwidth
  • 2006 5th May – Amazon reply to say that this ‘is in the works’. The plan is to enable you to cap the monthly charges.
  • 2006 – Other’s join in the conversation saying they would like the bill capping feature.
  • 2006 14th September – Amazon say the feature is ‘forthcoming’ but that they have no update on timing.
  • 2007/2008 – More people request the feature or updates from Amazon.
  • 2008 3rd June – Amazon reply saying it is still on their list of things to add but that they don’t expect to release it this year.
  • 2008 – A few more customers request the feature.
  • 2008 25th October – Amazon reply again saying it is still on the list, but they have no date to announce.
  • 2008/2009 – A few more customers request bill capping on AWS.
  • 2009 23rd March – Amazon reply and say the feature has been calendered to appear late this year or early next year.
  • 2009 3rd June – Amazon reconfirm the late this year / early next year timeframe in reply to another poster.
  • 2009/2010 – Many more replies from customer requesting some kind of cost limiting feature.

What can Amazon do?

Firstly they could make it possible to reduce the allowed bandwidth and number of hits. As the connection is already throttled, and as it is possible to increase the values, I’m sure it wouldn’t be that hard for them to allow you to reduce the limits.

And secondly they could allow you to configure a cost limit per day/week/month. Perhaps with a warning when 70% of your bandwidth is used up for example. This is what many metered web hosts do if you are near their limit.

A combination of both of these would probably be a good solution for most people who are worried about their potential bills.

Also as I previously mentioned it would be good for them to have clear public policies of what would happen if your account were hit by a DDOS attack leading to an unusually large bill.

What can I do?

If you are concerened you can add your voice to the discussions happening on the AWS forums, or try to contact Amazon directly to request these cost control features.

You can sign up for a 3rd party AWS monitoring service, which could notify you if the costs go abover a certain amount.

And finally

I’ll stress again that this problem is by no means unique to Amazon. In fact I’m not aware of any utility comuting provider that allows you an easy way to limit your costs, or throttle your usage. Therefore it won’t help you if you to change to another similar company.

I’m not saying that you shouldn’t use these services; in fact they are very useful and usually work well with good reliability. Just be aware of the risks.

Most importantly check your AWS account very regularly to monitor your costs.

Update: 11th May 2012

Amazon have now introduced automatic billing alerts. These won’t stop your charges from going up, but at least you will be notified if your pre-set limit is reached. See

Update: 8th June 2012

They have now introduced a billing data API

Still no way of forcibly capping the charges to a pre-determined amount, but they are at least providing more ways to monitor the charges.

2012 staff holiday planning spreadsheet

Monday, April 11th, 2011

This staff holiday planning spreadsheet is a 2012 updated version of my 2011 staff holiday planner. This time the formulas for calculating the remaining holiday are in the default sheet – if you don’t need them you can just delete the columns.

2012 staff holiday planner xls

As before the calendar planner shows the whole year left to right, with employee name down the side. As there are 365+ columns (for the days) you’ll need a spreadsheet package like Microsoft Office 2007 or OpenOffice to view the whole year. If you try to view it with a very old package like Microsoft Office 97 the year will get truncated after 256 columns.

Week numbers are listed according to ISO 8601. The top and side areas are frozen to make navigation easier, and there are some pre-prepared categories at the top left that you can copy and paste to the relevant cells (Ctrl-c, Ctrl-v are the shortcuts). Filtering for role and staff member name is set up as well.

Download 2012 staff holiday planner – XLS 22kb

The total number of holidays for the staff member can be entered into column C, and then column D automatically shows how many holiday days are left. You can replace the formula in column D if you want behaviour different to the default.

Count full day holidays and half day holidays

This is the default formula for cell D6 which counts whole and half holiday days.


Count holidays only

If you want to use this formula paste into cell D6 and then copy down.


Count holidays plus sick days


Count holidays plus sick days (with new ‘Half’ holiday value which subtracts 0.5 days)


OpenOffice Err:508

If you are using OpenOffice then you need to convert the commas in the above formulas to semi-colons. e.g. =C6-(COUNTIF(G6:NG6,”=Holiday”)) would change to =C6-(COUNTIF(G6:NG6;”=Holiday”)). Formulas that are in the default spreadsheet will work, this just applies to newly added formulas.

NatAmi ‘Native Amiga’ interview

Wednesday, March 23rd, 2011

Peter Kaltstein, Software Developer, talks to reviewmylife about the NatAmi project and the Amiga computer.

1. What is the NatAmi project?

NatAmi stands for Native Amiga and is a reimplementation of the former Commodore Amiga design, aiming at more performance while still keeping low level compatibility. The original concepts are strongly tied to DMA and multiple programmable special purpose chips.

natami amiga board

Thomas Hirsch started with his idea in 2003, first as an Amiga compatible disk controller that evolved into a full AGA Amiga implementation by time. His main motivation was that he wanted to have Amiga back, but also the technical challenge itself.

2. What is your role and how did you get involved?

I met Thomas first, when we were both working in a computer company in Böblingen in 2007. Seing his early prototype in action convinced me to join to help revive the Amiga.

Because of my Linux skills, I have set up the Natami server and development infrastructure – both for public and team internal usage. We use IRC, TRAC and Subversion to synchronize work. As a software developer I am looking forward to getting my Natami MX-board soon, when OS & application development can start.

3. Who are the key people involved in the project?

Thomas is the PCB and chipset designer. The 68050 is done mostly by Jens and Gunnar. Andi, Keith, Jens, and Gunnar wrote 68k testcases for it. Many team members joined and helped the project: Bartek did the graphics for the 2D demo game prototype and web banners, while Guillaume is a professional musician and contributed his own compositions for Natami. Additional members help on programming and more.

4. How was the hardware specification for NatAmi decided?

The 1st design based on 68060 originally included the CPU socket and SDRAM. Since this design would have been very expensive it evolved into a more modular concept and also switched to DDR2 memory.

Jens and Gunnar started developing a softcore 68k highend CPU, that is included into the same FPGA containing the Amiga compatible chipset. This makes the CPU-card with a physical 68060 optional.

natami amiga circuit board

5. How do you organise the work amongst yourself?

Since this is a spare time project, we organize work items in the internal side of the web forum and on IRC.

6. Are you getting any input from the original Amiga designers / programmers, or are you working everything out yourselves?

Everything is done by ourselves based on public specifications.

7. How do you go about designing the chipsets to be compatible with the original Amiga chipsets?

We can’t give a compatibility percentage yet but any game that already runs on a 68060-AGA-amiga is very likely to run also on Natami. With WHDload there is already a project improving compatibility of the old games and this project also helps the games on Natami.

8. What are the most challenging parts of creating NatAmi?

It is difficult to name only one but here are some examples: For Thomas a lot of effort was needed in adapting the Amiga chipset to make use of a pipelined DDR2 memory controller. As another example Jens spent quite some effort on an efficient CPU-cache design on the N050.

9. How is the NatAmi project financed?

Everything is financed privately. Thomas payed all the prototypes and parts he ordered for stock by himself. However the biggest sacrifices are the working hours spent. Since the journey is the reward, this makes a project possible, that otherwise would only be possible with a big investor.

10. How and when will Amiga fans be able to get hold of a usable NatAmi retail device?

Currently Thomas is ensuring that all components on the MX-board are working. Afterwards the board can be distributed first to team members and then after additional testing and driver development to the public. Please understand we can’t provide an exact date yet, but we will publish on in our news blog, when ordering can start and provide more info when the team-internal board testing starts.

11. Will Amiga fans that have old games or applications on 3½ inch floppy disks be able to use them with NatAmi?

3.5″ disk games already booted on the 1st Natami prototype and are still supported on the latest board, the Natami MX. However many will probably prefer to copy them to harddisk-images or use a compact flash onboard.

12. What do you think the retail NatAmi device will look like?

As of now the Natami MX design with its current configuration is decided to be the board that will be sold. Additionally to the LX the MX features Gigabit LAN onboard and also USBv2.

13. Why is the Amiga still relevant today?

The OS and hardware were extremely sophisticated at its time and very much superior to the x86-PC. People have different reasons for wanting Amiga back. Replacing still used Amigas with a full compatible successor can be one. Another aspect of the retro-movement might result out of the fact that current systems appear bloated and are not always fast to use, despite of having several GHz of CPU clock and lots of memory.

Since AmigaOS is very fast, light-weight and friendly to use and was so much ahead of its times, it still can be a nice niche platform not only for retro-gaming but many other tasks and to develop for. On the Amiga a programmer has low level access to the hardware which is an interesting challenge and very efficient.

14. What Amiga’s do you own, and what was your favourite Amiga?

I still own an Amiga 4000 desktop. My machine history before is A1000 and A2000. Actually every Amiga I owned was great at its time for me, but I have to admit, that up from 68060 times on, I also started using Linux and continued to use it on PowerPC.

For more information visit the website. Photos used with permission of the NatAmi team.

Three point estimation spreadsheet

Saturday, February 12th, 2011

If you are trying to make a three point estimation spreadsheet for Excel but are struggling with the formulas, then this free Excel download that I’ve made may help you.

three point estimation person spreadsheet

It has fields set up for entering data such as the task name, person responsible, and then the best, worst, and most likely estimates. You can also enter a contingency value as a letter. One of the spreadsheet tabs lets you set what percentage of contingency applies for each letter.

three point estimation contingency

If you like your estimates to be based on the most likely plus the contingency, you’ll see this automatically calculated for you in the first yellow columns (you may have to copy the formulas down as far as you need them).

If you prefer your estimate to be based on E/SD/Confidence values you’ll find them to the right of the sheet. Also available are the average and standard deviation (of the best/worst/most likely). The second yellow column is the 98% confidence plus contingency value.

three point estimation confidence values

Finally if you want to see a quick summary of how much work is allocated to each person there is a tab which gives you this information.

three point estimation person view

This spreadsheet is by no means ready for immediate use, you’ll probably want to customise it, remove the columns that you don’t need, and verify that the formulas do what you want and are correct. But at least it may help you produce the three point estimation spreadsheet you want more quickly.

Download the three point estimation spreadsheet – Excel XLS (16kb zipped)

It has been tested on Microsoft Excel 2007 and is a free 16kb download.

2012 One Page Excel Calendar

Wednesday, December 22nd, 2010

At the time I write this 2010 is nearly over, which means that 2012 is just over a year away. If you are planning far in advance then you might appreciate this free downloadable 2012 one page Excel calendar. If 2012 is too far ahead then I have a 2011 one page excel calendar available for download as well.

2012 excel calendar

Just like in previous years this calendar features the whole year on a single page. It should fit on your computer screen, but you might need to adjust the zoom depending on your default settings.

There are two versions, one is plain, and the other has the UK bank holidays marked on it.

2012 one page Excel calendar – blank
2012 one page Excel calendar – with UK bank holidays marked

Both version of the calendar are free to download, and should work on Excel 97 and above, or on OpenOffice (which you can download for free).

2011 monthly calendar for Excel

Friday, December 17th, 2010

Here is a free monthly calendar for 2011. You can download it as a XLS spreadsheet for Excel, Open Office, or whatever spreadsheet application you use.

I’ve previously produced a one page calendar for 2011, but I had a request to produce a month by month version, with each month on a separate tab. Here is what September 2011 looks like.

2011 monthly calendar

And here is a zoomed in picture of the calendar months listed on the tab at the bottom.

2011 monthly calendar zoomed

It is a free download, and only 13kb zipped up, or 96kb uncompressed.

The days of the week are along the top in a frozen pane, and the weeks are along the side. I’ve put the week numbers in as well (ISO 8601 week numbers if these things matter to you).

Download the 2011 monthly calendar – Excel XLS (13kb zipped)

This calendar should be viewable on Excel 97 and above.