How system data is extracted from the galaxy and system seeds
Famously, Elite's galaxy and system data is generated procedurally, using a set of three 16-bit seed numbers and the Tribonnaci series to generate entire galaxies of systems like this:
You can read all about this process in the deep dives on generating system data and twisting the system seeds.
The three seeds are stored in QQ15 (for the selected system) and QQ21 (for system 0 in the current galaxy) as little-endian 16-bit numbers, so the low (least significant) byte is first followed by the high (most significant) byte. That means if the seeds are s0, s1 and s2, they are stored like this:
low byte high byte s0 QQ15 QQ15+1 s1 QQ15+2 QQ15+3 s2 QQ15+4 QQ15+5
In this documentation, we denote the low byte of s0 as s0_lo and the high byte as s0_hi, and so on for s1_lo, s1_hi, s2_lo and s2_hi.
The seeds for the selected system are stored at QQ15, while the seeds for the current galaxy are in QQ21.
Here's a summary of which bits in which seeds are used to generate the various bits of data in the universe. The routine names where these data are generated are shown on the right.
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo
76543210 76543210 76543210 76543210 76543210 76543210
^^^----------- Species adjective 1 TT25
^^^-------------- Species adjective 2 TT25
^^----------------^^--------------------------- Species adjective 3 TT25
^^--------- Species type TT25
^^^^^^^^--------------^^^^--------- Average radius TT25
^^^--------------------- Government type TT24
^^--------------------------------------------- Prosperity level TT24
^----------------------------------------------- Economy type TT24
^^--------------------------- Tech level TT24
^^^^^^^^--------------------------- Galactic x-coord TT24
^^^^^^^^--------------------------------------------- Galactic y-coord TT24
^-^---- Long-range dot size TT22
^ Short-range size TT23
^------------------------------------------ Name length cpl
^^^^^--------- Name token (x4) cpl
^^^--------------------------------------------- Planet distance SOLAR
^^^--------------------------- Sun distance SOLAR
^^--------- Sun x-y offset SOLAR
76543210 76543210 76543210 76543210 76543210 76543210
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo