Because you have to turn down the volume as well as putting it on mute – plus why the way computers count restricts how much space there is on an external hard drive and dealing with the menace of the Heartbleed bug
To silence your iPhone, press mute - then lower the volume. Photograph: Andrew Gombert/EPA
Q Why does my iPhone still make sounds when the mute switch is enabled? Jemima, via email
A The iPhone mute switch can be a misleading feature as its behaviour is not as you may expect. You would assume that enabling it would cause all sounds to be silenced, but it mutes only notifications, system alerts, game audio and similar. Things such as video, music and some application sounds will be still be played; if you need to silence these as well, you'll have to lower your volume too.
Q I bought an external hard drive and it has less space than advertised, why is this? Leanne, via email
A The primary issue here is the difference between number bases. We usually write numbers using base 10 maths, using the symbols for 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. For example, 55 means 5 tens and 5 units. However, numbers can be written in any number base. For example, base 2 (or binary) is represented using only two symbols, 0 and 1, making it perfect for computers to represent using electrical signals. Just like Base 10, numbers have place value and columns represent powers of 10. So in Base 2, the columns represent powers of 2. Hence the number 110111 denotes (reading from right to left):
1 one (20), 1 two (21), 1 four (22), no eights (23), 1 sixteen (24), and 1 thirty-two (25). Therefore, 110111 in Base 2 = 55 in Base 10.
As computers operated in base 2, in the 1970s Microsoft adopted a 2n system for measuring storage capacity, using 1024 bits to a byte (210), 1024 bytes in a kilobyte (220) and so forth. However, since most consumers do not think in base 2 maths, drive manufacturers use a base 10 measurement system, using 1000 bytes to a kilobyte (103), 1000 kilobytes to a megabyte (106).
This isn't too much of a problem with fairly small numbers such as a kilobyte, but each level of increase in the byte prefix also increases the total discrepancy of the actual space compared to the advertised space.
So, if we measure this difference for a gigabyte, for every gigabyte a manufacturer claims, they are over-advertising by about 72 MB of disk space. If a manufacturer says a drive is 500 GB (500bn bytes) hard drive, the actual disk space is around 465 GB.
Annoyingly, this isn't true for all drives and storage media on the market. Consumers beware. Most hard drives are reported based on the advertised values where a gigabyte is one billion bytes. However, most flash storage is based on the actual memory amounts, so a 512MB memory card usually has exactly 512 MB of capacity. More confusion, and it would be much better if all manufacturers began reporting on actual disk capacity.
Q I saw something about a security flaw called "Heartbleed". Am I safe? How do I fix it? Adam, via email
A This bug is a vulnerability in the OpenSSL cryptographic software library used by most web software. This allowed the stealing of information that is usually protected by the SSL/TLS encryption that protects secure internet traffic (wherever you see https:// or the green padlock in your browser).
The purpose of SSL/TLS is to allow two computers to speak to each other without allowing others to see the conversation. SSL/TLS uses public key cryptography to secure communications for things like online banking, web services, online shopping, email and more.
Heartbleed allows anyone on the internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL library. This compromises the secret keys used to identify the service providers and to encrypt the traffic, names and passwords of the users and the content. This lets attackers eavesdrop on communications, steal data directly from the services and users and to impersonate services and users.
Fortunately, an update to the library has been released and many services have updated to a newer version. Many have also regenerated their certificates and revoked old ones to prevent any that may have been stolen from working in the future (as long as your browser checks for revoked certificates).
To protect yourself from any long-term effects, you should change all your passwords in case they were leaked and recorded while the vulnerability was widespread. Thankfully, doing this on sites that are not yet updated would make the process futile. However, a web developer named Jamie Hoyle released an extension for Chrome called Chromebleed that checks to see if the site you're visiting is vulnerable to Heartbleed and notifies you if it is. You can find it here .
It is also a good time to switch to using a good password management system such as 1Password to generate and store unique passwords for each site.
Daniel Tomlinson is a freelance programmer for iOS and web. He is a student and has been coding since he was eight. He is an ambassador for Young Rewire State and can be found @DanToml. Email your tech problems to Daniel: tech.questions@observer.co.uk with your name and address.
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