all it is is a way to identify the file as one you/I made, GDT is a contraction of Game DaTa, I used it to make it easy to find any game data saves, when your programs get larger and you have level data and encrypted media files etc in the folder, you know a GDT file is saved game data, you can make up your own "file format", for example GDT files save the position and scale of the player as four floating point numbers, if you want to add more data to the savegame file then feel free to go ahead, you could even save your data as .SGD (Shafan Game Data), one of the cool things about being a coder is you can get to make your own designer file formats named after your own humble self
for example you could save your text file but instead of using the .txt ending, you could save it as "gamedata.DVD" (Digital Videogame Data
)or "gamedata.abc" or "gamedata.nakedhamster" or whatever you please (though your helpline would get a lot of weird calls about the "nakedhamster" file format), the habit of using three letters to identify filetype goes back to DOS days when you where allowed eight letters for the filename and three to identify the filetype, so all computers had files like gvmntrpt.txt or topsecre.txt, nowdays the filesystem can handle larger extensions but people stick to 3 characters for backwards compatability (although only people with windows 3.1 or dos are going to appreciate this
)
In summary .GDT was something I just made up on the spur of the moment since I had to call the file something, since it`s a custom file I could have just called it "savegame" and left off the file extension. but extensions allow you write code to list all the saved games for your player to select one etc, much more useful than trying to work out if "somethingimportant" was a save game file or the users ID or the network settings or a music file etc, to make a save game file all you have to do is write all your data in order then read it back in the same order, you can add a few numbers to confuse hackers and check for altered files to stop loading if someone tries to cheat etc, it`s all up to you.
heres a simple example, I want to save the game state and hi-score table for a simple shooter game, I want to save the level, the number of current enemies and the players health and position, plus the top 5 scores, all I do is something like this
open to write 1,"supergame.savedata" <<< creates a file with this name
write word 1,level <<saves the level number
write word 1,enemies <<number of enemies
write word 1,health <<current health of the player
write word 1,position x
write word 1,position y <<<the x and y positions of the player
for i=1 to 5 << now we write out the score table
write long 1,hi(i) <<the score
write string 1,hi$(i) <<the players name
next i
close 1 <<finished with the file, this is the end of it
then all you have to do is to go through the list in the same order and load them back to the same values, and thats your home made file format, there is nothing to stop you doing
open to write "textfile.txt"
for i=1 to 5000
write word 1,rnd(255)
next i
close 1
which will make an unreadable .txt file on your hardrive, what it does is save numbers in a file called .txt, but not in txt format, so word thinks it`s a text file cos of the extension, and tries to read it, all you see is gibberish, a mixture of letters and numbers, since word can`t understand the file, hope that explains it somewhat.
Mentor.
PC1: P4 hyperthreading 3ghz, 1gig mem, 2x160gig hd`s, ATI radeon 9800 pro gfx, 6 way surround sound, PC2: AMD 1.2ghz, 512mb ram, FX5200 ultra gfx, stereo 16 bit soundblaster, ups.
