Formal word for "Home Made"

I'm seeking a more professional replacement for the word "home made". I'm writing my dissertation and I want to explain how I first used a home made code to simulate my project, as apposed to using a built in toolbox that comes with a professional program (which I use later).

I cant use the words "custom" or "bespoke", as the toolbox is extremely flexible and can be used to create custom and bespoke simulations (which is the reason I end up using it over my original code), so I don't want to cause confusion by using these words.

I basically just want a word that distinguishes the difference between a simulation I made myself from scratch, and a simulation made using a professional program.

I would say "I authored custom source code to simulate…"

I would use self-written, as in self-written program or self-written software.

I wouldn't use 'code' in a formal situation as it is an ambiguous abbreviation of any of source-code, machine-code, assembler-code, p-code or many other software related constructions.

Consider amateur.

amateur: characteristic of or engaged in by an amateur; nonprofessional.

I think the situation depends. Just yesterday I was told that I have a new boss (I never really report to anyone so I get passed around the company - 12 bosses in last 8 years). The new boss asked what I had using MySQL. I responded, "I have about 20 sites. About half are WP and the other are home made apps." I think in this circumstance it is formal because the business is the home.

Now does it translate to being formal when one programmer creates their own code. Being in the business I would be perfectly fine with it. And if I heard something too formal I might cringe at the buzz-wordiness. I have used custom-authored code/script before and it might fit your case if you don't want to use home made.

I wrote a custom-authored calendar app to keep track of when my dog needs to go outside.

But to me, this sounds just as good/formal...

I wrote a home made calendar app to keep track of when my dog needs to go outside.