Identifying specific items.

I’ve just started and I would like to have the player equip and unequip different armours for a mideval setting and have this displayed when they examine themselves, how would I go about doing that?

By looking around I could not come up with any specific ways for the description to change reflecting your worn armour, would I need to write specific lines for each piece of armour? Or is there a more efficient way of doing it.

if the player wears a guarder, say “You’re wearing your [armour].” instead;

The “guarder” is reffering to the armour in question here, the [armour] is where I would like the name of the armour (metal armour, leather armour, chain mail, etc.) to go.

You’re going to want to hook into the ‘taking inventory’ action.

Carry out taking inventory:
   Loop through everything held by the player; print special lines for armours; mark them somehow so they don't appear again later.

You’re likely going to have to completely replace the inventory-listing functionality.

No you won’t, not if you want that to appear when the player examines themselves. You could hook it on to “Instead of examining the player” or just put it in the player’s description if you want.

There are a lot of ways of doing it, depending on what you want to do and what your underlying code is. Here’s a simple one (I think, I haven’t tested it):

The description of the player is "[if the player is wearing an armour]You're wearing [list of worn armours][otherwise]You're unarmoured[end if].

This presupposes that you’ve defined “armours” as a kind of thing. See section 5.5 of the documentation for more on using lists in this way.

That was almost perfect, I was able to get it thanks to that, how I got it was

A guarder is a kind of thing that is wearable. The plural of guarder is guarders.

Leather armour is an gaurder. It is worn by the player. 

Metal Armour is a guarder. It is in Descending Stairs.

The description of the player is "[if the player is wearing a guarder]You're wearing [list of worn guarders][otherwise]You're unarmoured[end if]."

That allowed me to swap out the worn item and have the description reflect that, thanks.

Glad I could help! A couple more points:

Be careful of your spelling! I see you have it spelled “guarder” sometimes and “gaurder” other times – that can really ruin your day.

You might want to make sure that the player can’t wear more than one guarder. If you want to allow for more than one type of armor – helmets, boots, gloves, etc. – you could look at the Layered Garments extension, which lets you define lots of different types of clothing and ensure that some can be worn over others and some can’t be worn together. But that might be overkill.

Layered Garments is probably overkill - it’s really designed for when you have some types of clothes on top of other clothes.

If all you really need is to ensure the player has one suit of armor, one pair of boots, one helmet, one pair of gloves, etc. at a time, take a look at Example 44 in the documentation (“Get Me to the Church on Time”).

Thanks for the extra tips, I didn’t notice that spelling mistake, I don’t quite get how the spelling in Inform 7 game mode works sometimes, I’ve had it accept a L as a K before (it accepted “Drop Spoiled Mill” as “drop spoiled milk” or something similar).
I was looking into having layerd clothes, found simple rules that allow you to do that, without using the extension since you can specify what’s above and below, I don’t need anything too complex.
I was already looking to adapt that rule from “get me to the church on time”, since for the most part, I try to find anything I can to help me online first before asking, but I couldn’t find anything that told me how to do what I wanted to do in this case.

How I saw ‘examine selves’ and read ‘inventory’ I have no idea. I guess ‘guarder (worn)’ is good enough for the inventory?

As a rule, Inform 7 wants exact matches. However, it only cares about the first 9 letters (or other characters) of each word in a name; so it wouldn’t distinguish between ”spoiledmilk” and ”spoiledmill" or between “Sauerkraut” and “Sauerkrauz” (though it should distinguish between “spoiled milk” and “spoiled mill” and between “Sauerkraut” and “Sauerkrout”).