The iPhone and iPad are black boxes. You switch them on and they work, except when they don't. Then you are struggling to find out what the problem could be. Use these diagnostic tools.

What goes on inside iOS devices is almost a complete mystery to most people. You can view a list of the amount of storage space used by apps, and view a list of apps that use the most battery. These features aside, it is still a mystery how the hardware works or even if it works. Although some hardware problems are obvious, others are not and tracking down problems is not easy.

Apple clearly does not want people to be concerned by what goes on inside their iOS devices, but some people do not like not knowing. If you know that there is a shortage of memory or storage, or that the processor is being worked flat out, it means that you can set about solving the problem. For example, closing apps in the background, uninstalling software, stopping run-away apps that are hogging the processor and so on.

Phone Doctor Plus

Price: Free | By: Idea Mobile Tech Inc. | Size: 17MB | iOS: 8.0 and up

Phone Doctor Plus is a free iPhone app that enables you to see what is going on inside the iPhone and iPad and to test the hardware. There are several sections and the order in which they appear is confusing at first. I nearly uninstalled the app thinking it didn't work, but it is actually OK, you just need to use the modules in the right order.

The home screen, the first tab, can be ignored. The status screen, the second tab, should also be ignored the first time the app us used. Instead, jump to the Interaction screen, the third tab and tap the right arrow near the top. This provides a list of hardware tests that you can perform on the iPhone.

There are many items and each one checks a specific hardware component. For example, you can check that the microphones (there is more than one) are working, you can check the audio volume buttons work. You can test the front and rear cameras, normal and wide angle, camera flash, face detection, sleep/wake button, accelerometer and gyroscope and so on. The screen’s touch multi-touch capabilities can be tested, the compass and proximity sensor tested. The screen can be tested for dead pixels, and so on.

There are over 30 tests and each of them is very simple and sometimes you have to press the screen, press buttons, wave the phone around to trigger sensors and so on. Some of the functions display hardware information such as the amount of RAM and the speed at which it can be accessed, the read and write speed of the storage, the CPU model, number of cores, architecture and performance rating. It is slightly technical, but you do not need to be an expert to understand it.

You could use these tests to identify a problem with an aspect of the hardware, such as a malfunctioning proximity sensor, gyroscope, touch screen and so on. It can also be used to get hardware information so that you can compare it to other iOS devices.

After performing all the tests, you can then go to the Status screen, the second tab, and view the items. It shows the remaining battery time, storage usage, CPU usage, memory used and free, and network usage. Tapping any of these opens a new screen to show the details, such as a breakdown of memory or storage usage, or the load each CPU core is experiencing.

Viewing the status before running the hardware tests results in missing information, which was confusing - run the tests! The Status items are also a bit slow to display, which also added to the confusion. Once I realised what was going on, this app was found to be very useful. If you want to know what is really happening inside your iPhone and iPad, check the hardware, monitor usage and get other information, this is an excellent tool.

Phone Doctor Plus is useful for the more technically minded iPhone and iPad user.

Phone Diagnostics

Price: Free | By: HITEK NOVA | Size: 44 MB | iOS: 8.0 or later

Phone Diagnostics is another free tool in the iOS App Store that enables you to test the hardware components in the iPhone and iPad. It is easy to use and the home screen gets you straight to the testing modules of which there are over 30.

That is a lot and there is plenty to do when you first run the app and you can either use the big arrow button on the home screen to run them all or you can select individual ones, so if you suspect a particular problem with the iPhone or iPad, you can run the module or modules that tests it. For example, there are several that test the screen in various ways.

There are modules like like volume up and down buttons, multi-touch capabilities, mute switch, front and rear cameras, ultra wide camera, all the microphones, motion sensors, flash, vibration and so on. Tests run for about 10 seconds each and if the device passes, a green tick appears on the module on the home screen. You can easily see which components passed and which failed and you can run a module again to test it again.

That is about it and Phone Diagnostics simply runs tests on iPhone or iPad components. The pass or fail state is shown on the home screen. This is another useful diagnostics app. It is ad-supported, but they don't get in the way.