Solve : Hard Drives and FAT help?

1.	Solve : Hard Drives and FAT help?
Answer» I know that what ever the SIZE of the hard drive the nuumber of sectors it will have changes. But am I right that nomatter what the size of the hard drive FAT 16 will put use 65,526 clusters? And nomatter what the size of your hard drive FAT 32 will only use 524,408 clusters?I must be mad but I'll run it past you one more time... This quote was posted in response to your query here.. on the 2nd of this month... Quote # FAT12: The oldest type of FAT uses a 12-bit binary number to hold the cluster number. A volume formatted using FAT12 can hold a maximum of 4,086 clusters, which is 2^12 minus a few values (to allow for reserved values to be used in the FAT). FAT12 is therefore most SUITABLE for smaller volumes, and is used on floppy disks and hard disk partitions smaller than about 16 MB. # FAT16: The FAT used for most hard disk partitions uses a 16-bit binary number to hold cluster numbers. When you see SOMEONE refer to a "FAT" volume generically, they are usually referring to FAT16, because it is the DE facto standard for hard disks. A volume using FAT16 can hold a maximum of 65,526 clusters, which is 2^16 less a few values (again for reserved values in the FAT). FAT16 is used for hard disk volumes ranging in size from 16 MB to 2,048 MB. # FAT32: The newest FAT type, FAT32 is supported by Windows 95's OEM SR2 release, as well as Windows 98. FAT32 uses a 28-bit binary cluster number--not 32, because 4 of the 32 bits are "reserved". 28 bits is still enough to permit ridiculously HUGE volumes--FAT32 can theoretically handle volumes with over 268 million clusters, and will support (theoretically) drives up to 2 TB in size. However to do this the size of the FAT grows very large. If you format a Drive that is 512 MB it will defalt to FAT 16 why both FAT 16 and 32 can use a 512 MB Drive so why defalt to FAT 16?Quote why defalt to FAT 16? Because that's the FAT system which allows the most efficient cluster addressing on that size of disk. So let's look at it again. Quote A volume using FAT16 can hold a maximum of 65,526 clusters, which is 2^16 less a few values (again for reserved values in the FAT). Quote FAT16: The FAT used for most hard disk partitions uses a 16-bit binary number to hold cluster numbers. The maximum number of clusters is 65,526 and a 16-bit binary number is used to address them so the highest number addressed (65,526) is 16-bit binary 1111111111110110 (or splitting it into 2 bytes just so that it's easier to view 11111111 11110110) Quote FAT32 uses a 28-bit binary cluster number--not 32, because 4 of the 32 bits are "reserved". Fat32 uses a 28 bit binary number to address clusters, the highest cluster address which can be addressed is binary 00001111 11111111 11111111 11111111 (I'll leave you to work out what that value is in decimal. Note that the binary shown is just a representation, the 'reserved' bits could appear anywhere in that representation) so the highest address is way outside the capacity of what are now known as 'small' hard drives, therefore no point in defaulting to the Fat32 system. Also the FAT (that's the actual File Allocation Table itself) would be twice the size it needs to be for that capacity hard drive. Drive and cluster sizes will have been considered when the Format program you are using was designed. Also, remember that the Fat32 system was probably not around when the Fat16 system was designed, large capacity hard drives were simply not available. You really should get down to reading this if you want to understand about the format of disks and File Allocation Tables. Here's another bit of reading with a table showing drive size and default cluster sizes.

Answer»

I know that what ever the SIZE of the hard drive the nuumber of sectors it will have changes.

But am I right that nomatter what the size of the hard drive FAT 16 will put use 65,526 clusters?

And nomatter what the size of your hard drive FAT 32 will only use 524,408 clusters?I must be mad but I'll run it past you one more time...

This quote was posted in response to your query here.. on the 2nd of this month...

Quote

# FAT12: The oldest type of FAT uses a 12-bit binary number to hold the cluster number. A volume formatted using FAT12 can hold a maximum of 4,086 clusters, which is 2^12 minus a few values (to allow for reserved values to be used in the FAT). FAT12 is therefore most SUITABLE for smaller volumes, and is used on floppy disks and hard disk partitions smaller than about 16 MB.

# FAT16: The FAT used for most hard disk partitions uses a 16-bit binary number to hold cluster numbers. When you see SOMEONE refer to a "FAT" volume generically, they are usually referring to FAT16, because it is the DE facto standard for hard disks. A volume using FAT16 can hold a maximum of 65,526 clusters, which is 2^16 less a few values (again for reserved values in the FAT). FAT16 is used for hard disk volumes ranging in size from 16 MB to 2,048 MB.

# FAT32: The newest FAT type, FAT32 is supported by Windows 95's OEM SR2 release, as well as Windows 98. FAT32 uses a 28-bit binary cluster number--not 32, because 4 of the 32 bits are "reserved". 28 bits is still enough to permit ridiculously HUGE volumes--FAT32 can theoretically handle volumes with over 268 million clusters, and will support (theoretically) drives up to 2 TB in size. However to do this the size of the FAT grows very large.

If you format a Drive that is 512 MB it will defalt to FAT 16 why both FAT 16 and 32 can use a 512 MB Drive so why defalt to FAT 16?Quote

why defalt to FAT 16?

Because that's the FAT system which allows the most efficient cluster addressing on that size of disk. So let's look at it again.

Quote

A volume using FAT16 can hold a maximum of 65,526 clusters, which is 2^16 less a few values (again for reserved values in the FAT).

Quote

FAT16: The FAT used for most hard disk partitions uses a 16-bit binary number to hold cluster numbers.

The maximum number of clusters is 65,526 and a 16-bit binary number is used to address them so the highest number addressed (65,526) is 16-bit binary 1111111111110110 (or splitting it into 2 bytes just so that it's easier to view 11111111 11110110)

Quote

FAT32 uses a 28-bit binary cluster number--not 32, because 4 of the 32 bits are "reserved".

Fat32 uses a 28 bit binary number to address clusters, the highest cluster address which can be addressed is binary 00001111 11111111 11111111 11111111 (I'll leave you to work out what that value is in decimal. Note that the binary shown is just a representation, the 'reserved' bits could appear anywhere in that representation) so the highest address is way outside the capacity of what are now known as 'small' hard drives, therefore no point in defaulting to the Fat32 system. Also the FAT (that's the actual File Allocation Table itself) would be twice the size it needs to be for that capacity hard drive.

Drive and cluster sizes will have been considered when the Format program you are using was designed. Also, remember that the Fat32 system was probably not around when the Fat16 system was designed, large capacity hard drives were simply not available.

You really should get down to reading this if you want to understand about the format of disks and File Allocation Tables.

Here's another bit of reading with a table showing drive size and default cluster sizes.

Solve : Hard Drives and FAT help?

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