Fat is a list of entries that map to each cluster on the partition. Some formatting programs allow the cluster size to be specified. The standard way to store and access data on sd cards is to use the ms fat file system. The table contains entries for each cluster, a contiguous area of disk storage. Fat partition boot sector contains information that the file system uses to access. The fixed assumption of 8 sectors per clusters on hard disks practically limited the maximum partition size to 16 mib for 512 byte sectors and 4 kib clusters. Fat 16 is used mostly in removable devices like usb drives, sd cards, xd cards, etc. From the chart we can see, the parameters of file system are all record in bpb parameter table of dbr. The default cluster size is determined by the size of the volume. Therefore, any larger cluster size would not allow for the conversion to function. Normally clusters are at least 4k 8 sectors, and sizes of 8k, 16k and 32k are also widely used. This should resolve to an acceptable number of sectors per cluster see below. Fat16 file system disk searching file in fat16 partition. The number of sectors per cluster is given in the boot sector byte.
The file allocation table has one entry per cluster. Lets see a boot sector start sector is dbr in fat16 after advanced format. A volume formatted with the fat file system is allocated in clusters. The total number of sectors as noted in the boot record can be larger than the number of sectors used by data clusters. If the fat cluster size is greater than 4 kb, then the clusters are converted down to 4 kb in ntfs. Fat16 indicates that the size of each entry in the file allocation table of a disk is 16 bits. The file system software itself will never actually use the second fat. An overview of fat12 the file allocation table fat is a table. The fat is a linked list of clusters, where each cluster chain represents a file. The number of sectors per cluster on fat16 is stored as an 8 bit. File allocation table wikipedia, a enciclopedia livre. It offers useful performance even in lightweight implementations, but. This is because the fat structures are aligned on cluster boundaries. File allocation table fat is a computer file system architecture and a family of industrystandard file systems utilizing it.
The fat16 file system with sd cards i have been working on a project where the client requires their device to have its firmware updated from a secure digital sd card. Things ive learnt the fat16 file system with sd cards. Cf card in either fat12 or fat16 format, with at least two sectorspercluster. I guess the needed space could be calculated, but trying e.
A fat file system is a specific type of computer file system architecture and a family of industrystandard file systems utilizing it. Note also when formatting a partition under windows nt 3. Various format utilities leave their own name, like chfor18. In other words, it uses 16 bits to address clusters. There are formatting requirements for cf cards which need to be met in order to. File allocation table fat is a computer file system architecture and a family of industrystandard. File chaining and fat cluster allocation the file allocation table fat is used to keep track of which clusters are assigned to each file. The operating system, and all installed software applications, can determine where data a file or all of the parts comprising a file is located by using the directory entry for the file and the.
Some later versions of microsoft windows allow using even larger cluster sizes, by effectively considering the sector size to be some mulitple of 512 bytes. Probably its what it says not enough clusters for a 16 bit fat. The dos formatting tool rejected such disks completely. Easily get your hard disk drive formatted in the fat32 system with the help of this lightweight but powerful software application. This entry uses 12, 16 or 28 bits for fat12, fat16 and fat32. Default cluster size for ntfs, fat, and exfat microsoft support.