First of all you need to work out every piece of infomation you need to save in order to recerate the game in the state it is in when the save was made. How difficult that is will depend on how you organised the game.
Then you need to decide what order to write the data into the file and what data types you will need to use.
WRITE BYTE - (1 byte) whole number from 0-255
WRITE WORD - (2 bytes) whole number from 0-65535
WRITE LONG - (4 bytes) whole number
WRITE FLOAT - (4 bytes) float
WRITE STRING - string
Once you have done that you need to open the file for writing, write the data and then close the file. Files have a number which has to be between 1 and 32, the same way that images and objects have numbers.
db is odd in that it requires that the file does not exist before opening it for writing, most languages will either overwite a file by default or have an option.
To open the file you need to check if the file you want to open exists and if it does delete it. Like this.
if FILE EXIST("save.dat") then DELETE FILE "save.dat"
OPEN TO WRITE 1,"save.dat"
save.dat is now open for writing as file 1.
Now you need to write data to the file. Say you had an extreamly simple game where all you needed to save was the players position and score. The position of the player is in the variables playerx#, playery# and playerz# while the score is in the variable score.
The format of the save file will be
float playerx#
float playery#
float playerz#
long score
To write the data you would do this.
if FILE EXIST("save.dat") then DELETE FILE "save.dat"
OPEN TO WRITE 1,"save.dat"
WRITE FLOAT 1,playerx#
WRITE FLOAT 1,playery#
WRITE FLOAT 1,playerz#
WRITE LONG 1,score
CLOSE FILE 1
Now you have a file that contains all the info you need to recreate the game in the state t was when the save was made. The code to read the file is similar to the code to write it except you use the READ commands instead of the WRITE command. To load the file saved above the code would be
OPEN TO READ 1,"save.dat"
READ FLOAT 1,playerx#
READ FLOAT 1,playery#
READ FLOAT 1,playerz#
READ LONG 1,score
CLOSE FILE 1
You also might want to add some error checking to make sure the file you want to load exists (use FILE EXISTS()) and to make sure the file isn't too short with FILE END(). You also might want to sanity check the data you are reading to prevent cheating, if the maximum health you can get in the game is 100 then check the value loaded from the file isn't greater than 100.
can i scream
