keystrokes for diagnostics check on macbook prro?

the answer depends on which model:

Older models that have never had their disk erased, hold the D-for-diagnostics key at startup, and it will be loaded off the original disk. Or insert the original 'shipped in the box' disk 2 of 2 and it will load off there.

If your Mac was introduced before June 2013, it uses Apple Hardware Test

How to use Apple Diagnostics on your Mac - Apple Support

Later MacBooks (after the date above) have Internet Recovery in their ROM, D-for-diagnostics will bring in Internet Recovery, which will download the diagnostic from the Internet (provided your Mac is working well enough to accomplish all that).

Later MacBooks (after the date above) have Internet Recovery in their ROM,
D-for-diagnostics will bring in Internet Recovery, which will download the diagnostic from the Internet (provided your Mac is working well enough to accomplish all that).
D what do you mean by that ? How to lauch Internet Recovery ? At Restart ? in this case, should be : d or shift + d

My Mac does not work well enough to accomplish all that. Because I do not have access to the Diagnostics whith such a Keystroke. In fact nothing happens. ( EL CAPITAN is the current Mac OS I'm running ) What was the preset OS at its first use?

[Personal Information Edited by Host]

For some reason it seems easier to remember an uppercase D, but that is not what you type. You type a plain lowercase d, and no modifier keys with it.

The key is the same, whether it comes directly off the disk or whether it is invoked through the Internet. But if your Mac is not working well enough to do Internet Recovery, you will need to take it in for service. Your appointment for an evaluation is Free at an Apple-owned store. Apple Authorized Service Providers sometimes charge a fee to keep you from using their services frivolously.

Your mac was issued with 10.9 Mavericks. It has Dual Graphics.

https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i7-2.6-15- dual-graphics-late-2013-retina-display-s…

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d at a reboot has no effect for a my MacBook pro 11,3 under OS X 10.11.6 (15G22010) 😕