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{{Major glitches}}
{{PRAMA|item-underflow-glitch}}
An '''expanded itemsitem pack''' is a [[glitch derivative]] in {{RBY}} and {{GSC}}; in which the player can access items at a position from beyond the maximum limit imposed by the game.
 
For example, in Red, Blue and Yellow the normal maximum number of bag items is 20 and the maximum number of stored PC items is 50 and under normal circumstances, trying to obtain another item will bring up a message that there is no more space.
 
In actuality, the maximum amount of items that the player can use, swap or toss is 255 or whichever value a 'number of items' address, such as D31D (Red/Blue, D31C (Yellow) (number of items in the overworld itemsitem pack) becomes corrupted to.
 
==Attributes of items beyond the item limit==
The items and quantities beyond the imposed item limit represent unrelated memory addresses with values interpreted as items or quantities. The memory addresses follow on as expected.
 
See the following articles for more specific information:
 
*[[Expanded bag item documentation (Generation I)]]
*[[Expanded PC item documentation (Generation I)]]
*[[Expanded bag item documentation (Generation II)]]
 
===Examples===
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Note that this equation does not apply for items 129 (0x81) through to 256 (0x00) because those items represent items 1-128 again.
 
== Returning a bag of 255 items back to normal (Generation I) ==
This is very simple : you need to buy three items to return your menu to normal.
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With [[arbitrary code execution]], the following code should work :
<br /pre>
<code>
Lemonade x(# of items in your inventory before the glitch)
TM34 x29 (x28 in Yellow)
<br/>
TM11 x201
TM34 x211
<br/pre>
hex:1C (Earth Badge) x201
</code>
 
= Generation I activation =
 
== Item underflow glitch ==
This method was discovered by MrWint.
To activate this glitch, the player needs, in their first two item slots :
<br/>
(Any cheap item)x any qty
<br/>
(Any item)x 255
 
Moreover, the player must have an item removable by an event (a drink for the Saffron guards, a fossil, etc.)
''NOTE'' : it is not recommended to have other items than these in your bag.
 
The player should open their item inventory, and toss their first item until the Item menu stops "responding".
<br/>
Then the player should remove an item from their inventory with an event. Then, opening the item pack allows the player to edit unrelated portions of the memory as if they were items.
 
=== Explanation ===
When the first item stack is tossed, the game decreases the owned item counter (located at hex:D31C) by 1. It then makes the item x255 erase the item tossed. But because dec:255 equals hex:FF and the game considers FF as the ending marker, the 255 items aren't overwritten, nor the following ones.
<br/>
The process repeats until the item counter reaches 0, which makes the first item act as the Cancel button. Then giving out an item makes the game decrease the item counter once more, which underflows to hex:FF. The player can then access 255 items, which is far beyond the normal limit.
 
=== "Dry" item underflow glitch ===
This glitch was documented by luckytyphlosion ([http://forums.glitchcity.info/index.php?topic=7175.0 thread]).
 
It is a better method because it doesn't require the Saffron guards to be thirsty or a Fossil.
<br />
Also, it can be done with the PC items, allowing one to edit more RAM addresses that could only be manipulated with [[arbitrary code execution]] or [[Map_254_(Yellow)|map FE]].
 
== Generation I activation ==
You will need 2 different tossable items, and a stack of 255 items.
Steps to reproduce :
<br />
# Order your items so that your 2 tossable items are in slots 1 and 2 and the item x255 is in slot 3.
# Toss everything below the item x255.
# Toss the top two items so you have three items x255 (item count=1)
# Toss 253 of the first item x255.
# Swap item 1 with item 2.
# Swap item 1 with item 2, again.
 
=== "Dry" itemBy underflow glitch ===
You can also do this with items below the third (and initial) 255 stack. You need to count how many items you have, then after step 3 toss the top item x255 the number of items you initially had -2.
There are two known ways of tricking the game into decrementing the item count when it is already 0, which causes the it to underflow to 255. Both methods require an item stack of something x255:
* [[Item underflow glitch (event method)]]
==* Item[[Dry underflow glitch ==]]
 
==== Methods to obtain x255 stack ====
== Expanded party list methods ==
{{MissingNo. underflow}}
 
=== By save corruption ===
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This glitch may stop working later in the game due to FF values appearing in the memory before the bag addresses.
 
=== By arbitrary code execution===
If you can use [[arbitrary code execution]] (ACE), you may run the following code for the English games (both with 8F for {{RB}} and ws m for {{Y}}).
<br/>
Line 128 ⟶ 98:
This basically changes the item counter to hex:FF.
 
=== Using Gameshark ===
UsingThe a cheating device is not needed, however, theGameshark code 01FF1CD3 (Yellow) or 01FF1DD3 (Red/Blue) will give the player 255 items.
 
=== By [[Glitch City RAM Manipulation]] ===
By having 50 slots filled in the PC, GCRM can turn this number to 109 ; it is then possible to retrieve a stack of 255 items, and perform either method of item underflow (see above).
 
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However, since the PC has 109 items accessible, storing items is likely to corrupt game data instead of returning the PC to normal. The best solution is [[Arbitrary code execution]], although retrieving 59 items from the PC will also work (but it's difficult).
 
== Generation II activation ==
{{incomplete}}
One can access an expanded Poké Balls pocket through [[duplicate key items glitch]] abuse.
 
== Notes ==
*In Red, Blue and Yellow, when scrolling down the list, the cursor may seem to freeze ; in that case hit B until the cursor responds again. (If A is used, and is pressed while a long-name item is selected the game will crash and save data may be partially overwritten.) This happens when the game prints a large name which spans multiple lines.
*In Pokémon Crystal, the glitch description of item hex:00 will usually freeze the game. This can be avoided if the player presses Select on another item to bring up the text "Where should this be moved to?" before scrolling down.
*The expanded itemsitem pack is useful for Pokémon 'glitched' speedruns as it allows the manipulation of many addresses such as map destinations, text pointers (for [[text pointer manipulation]]) and so on.
 
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