How many data lines are necessary in 16-bit microprocessor and what is the magnitude of the largest number that can be placed on its data bus?

The number of data lines required in a 16-bit microprocessor is 16, in the internal view, but could be something else, such as 8, in the external view. In the 8086/8088, the processor is 16 bits, and its internal data bus is 16 bits. The 8086 provides 16 bits on the external bus, but the 8088 provides 8 bits, even though they are the same internal processor - the 8088 simply uses two memory cycles to move one Word.

The largest number that can be represented on a 16 bit bus depends on the interpretation of that number. An unsigned 16 bit number ranges from 0 to 65535, so 65535 is the largest value when unsigned. A 16 bit two's complement signed number ranges from -32768 to +32767, so +32767 is the largest value when signed.