What is the major difference b/w 32-bit and 64-bit processor ??

At any time processor can execute only one machine instruction, and that instruction length is 32 bits in 32-bit processor and 64 bits in 64-bit processor.

The memory addresses represented by a 32-bit processor is 2power32(2^32) where as 2power64(2^64) in case of 64-bit processor.since 64-bit processor has more memory address, it can even load entire program into memory and executes the program by reducing the overhead of Disk I/O cycles, thereby increasing the performance.

(if not entire program, 64-bit processor will have large "frame" size compared to 32-bit. so it can execute the program in less Disk I/O cycles)