How do I reverse sequence the mobile phone numbers in the file?

/*************************************** ***************************
* Description: sorts the phone numbers in the file in reverse order. *
* Parameter: FP is the file pointer, and startlocation is the start position of the mobile phone number. *
* Return value: success; true; failure; false. *
**************************************** *************************/
# Define cell_phone_nums 11

Bool reversecellphonenumber (File * FP, long startlocation)
{
Int array [cell_phone_nums] = {0 };
Int CH =-1;
Long startlocationcopy = startlocation;
Int I;

If (null = FP)
{
Return false;
}

/* Read from the file */
For (I = 0; I <cell_phone_nums; I ++)
{
Ch = fgetc (FP );
If (CH = EOF)
{
Return false;
}
Array [I] = CH;
}

Fseek (FP, startlocationcopy, seek_set );
/* Write back into the file */
For (I = CELL_PHONE_NUMS-1; I> 0; I --)
{
Ch = fputc (array [I], FP );
If (CH = EOF)
{
Return false;
}
}

Return true;
}