Hi,
Could you please tell me the diffrence between the knime external node which is coming under the misc and knime Lab.Thanks in advance.
The node in "non-labs" is based on plain CSV input and output.
The one in Labs was developed as part of some contract work and is only the tip of the iceberg. The node itself supports different in/output formats (CSV and two chemistry types in the standard installation), it supports chunking (parallelism) ... but also has a major requirement: It appends the computed result data to the input data as extra new columns. If you run Linux or Mac there is a good example on the public example server (search for "045001_External_Tool-Linux_or_Mac_only").
In fact, it's an entire API framework. It's extensible (meaning you would need to write extra nodes/java to make use of it): You can define custom input/output types (like chemistry data type formats), a custom dialog and a custom executor (don't run locally but in a compute cluster).
The development was sponsored by a pharma customer - they have 20+ different tools that do some fancy chemistry property calculation (completely not my domain - don't ask details) and for each of these tools they wrote a wrapper based on this framework. So their users don't use the tools directly but through KNIME.
The node is still in labs because its usage, specifically the requirement to append columns as opposed to generate completely new data, is a bit unusual.
Hope this helps.