Use data on SD card for controlling a servomotor

I see what you mean.
In fact I am a novice in arduino and C language, that's why it's a bit difficult for me to code this program.
I thank you for ur advices, but can u explain me quickly how to use them ?

char* val = "0";

By example, what should i put instead of that.

while(val >=0){           
       val[0]=file.read();

this must be deleted?

how to create a non-NULL-terminated array?
and a end of record marker ?

If you have a little time to dedicate to my program, could you correct my wrong things, this will help me a lot!
ty