I would like to find a way to store an unsigned value most accurately so that I could reuse it when I seed my random number generator. Currently, I am writing it to a file. However I realise that what is stored will be dependent on the conversion specifier. Which conversion specifier will ensure the most accurate storage?

Code:
unsigned seedtime;

seedtime=(unsigned)time( NULL );// This will be the seed which I                                                    //require

appendfile(seedtime);

//code for appendfile

void appendfile( unsigned count)
{
	FILE *cfPtr;

	if ((cfPtr= fopen("updx.txt","a"))== NULL )
		printf ("File could not be opened\n");
	else{
			fprintf(cfPtr,"%u\n",count);
		}

		
	fclose(cfPtr);
	
}
Currently I am using %u but wonder if there is any other better and more accurate coversion specifier.

Is there any other method to store my unsigned seedtime so that I can use it again when I run my program?

Another question regards my fopen command . Is there any way I can change the directory in which updx.txt can be stored? Currently it is stored in my working directory but I would like to change it to my specification.

Thanx a lot in advance for any help.