The memory editor being used to write to RAM
K(ry's memory editor is one of the oldest known (and possibly first) fan-made memory editors for Pokémon Red, Blue, and Yellow, specifically designed for arbitrary code execution with glitch item ５かい in Pokémon Red and Green.
This memory editor was hosted on the website "Pokémon Bug Litches" (sic), also known as kattempla/pokebug.
Unlike later memory editors, including offgao's memory editor and TheZZAZZGlitch's memory editor (which use one large text box) the memory editor operates on two small text boxes. The first one (at the left side of the screen) is an adjustable memory address, while the second one (at the right side of the screen) is a typical quantity box. Setting a specific 'quantity' to the address will make the game attempt to write to the given address, which can be in RAM.
This memory editor allows for a basic 'in-built GameShark' effect in which the player can set any value to any memory address which they desire, although in order for the player to set up this program, it requires them to write 227 bytes beginning from D9B3.
The memory editor has not yet been ported to versions of Pokémon Red, Blue, and Yellow outside of Japan, and it is unconfirmed whether it works in Japanese Blue and Pocket Monsters Pikachu.