how save text file which is made by c and how add a new information in after saving it?

Ur question is completely unclear...!!!
Ar u talking abt appending text to an existing file ???

Simply Type

fclose(file_descriptor);

after manipulating with the file to save it...

And to append some data...
add "a" as mode in the fopen call eg:-

FILE *fd = fopen("file.txt","a");
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