I'm not one to mess around too too much with a game's asm or memory. So basically on my vba emulator there's a search for codes, etc, BLAH, BLAH, BLAH.... lol i know how it works! But the thing is, let's say, i found the address for it and for the value, (example) i can't go over a certain value like 255. i tried putting 9999, vba shows me an error. In HxD is there a way to have infinite xp after 1 battle, until i reach lv 100???
For values over 255 the game uses multiple bytes so any experience hack would likely need multiple bytes set to be usable.
Also of note is that such a hack would be useless in Gen1 if you plan on having level-up moves on your pokemon, and it will "miss" all the levels between the level it battles at and the level after the experience has been added.
If you must cheat to increase the level, then I would suggest simply modifying the amount of Rare Candies you have. If you wish to use Missingno for this (something I wouldn't recommend personally if you were using a physical cartridge) then the process would add 127 Rare Candies to your stockpile - IF they were in your 6th item slot. After a few Missingno encounters (make sure you deposit a bundle after every encounter) you'd have more than enough to max out a couple of teams.
Note that the reason I say to deposit a bundle between encounters is that the Missingno glitch set the most significant bit in the 6th item amount value to "1" - this means that if there's less than 127 of that item (there will be if playing normally), it will have the side-effect of adding 127 to it. If the value is 127 or more, then there'll be no effect.
R.I.P. Throwback Mode - 23rd April 2014 - We miss you. PAL Gamers unite - http://www.gamefaqs.com/boards/277-pal-gaming
But yeah, you want to take into factors that your pokemon will miss out on learning certain moves, evolution, and stat experience (EVs) by this method. THIS will hamper their potential unless you plan on hacking all that as well...
Sometimes you put walls up not to keep people out, but to see who cares enough to break them down.