What are the pros and cons of fixed-lengthand variable-length instructions? which is currently morepopular?

Explained

Explanation:

Fixed length instruction:

Advantage Of fixed length instruction that it is fast and results in better performance when level piping is used.

Disadvantage is that it wastes space.

Variable length instruction

Advantage is that it saves storage space.

Disadvantage is that it is complex to decode.

Currently variable length is more commonly used.