Background information $($ARM LANGUAGE$)$

In RAID $4$ and $5$ systems, a parity block is calculated for each group of blocks across multiple drives. The parity block is calculated by applying XOR.

E$.$g$.$ in a four$-$drive RAID $5$ system we could have

P$=$A$^$ B $^$ C

where A$,$ B$,$ C and P are blocks of data, anywhere from $512$ bytes to $128$MiB or more, based on

the cluster size.

Exercise $1$

Calculate the XOR parity of an array of numbers given in memory, e$.$g$.$:

n DCD $7$ data DCD $10,20,30,40,50,60,70$

The result should be a single $32$ bit number.

Store the result in memory $0$x$40000000.$

Use the RN directive to replace direct references to registers, with symbolic names.

Exercise $2$

Use the result obtained in the previous exercise to recover one of the numbers in the array $($assumed to be lost or corrupted$).$

For example, if we use just $6$ of the previous numbers and we perform a sequence of XOR operations between them and the parity found, we should get $40.$

n DCD $6$ data DCD $10,20,30,50,60,70$