The key features of an algorithm are:

1. Input: An algorithm should have a clear input, which specifies the data that the algorithm will work on.
2. Output: An algorithm should have a clear output, which specifies the result that the algorithm will produce.
3. Definiteness: An algorithm should be defined in a clear and precise manner, using a finite number of steps.
4. Finiteness: An algorithm should terminate after a finite number of steps.
5. Correctness: An algorithm should produce the correct output for all valid inputs.

The key features of a flowchart are:

1. Symbols: A flowchart uses standardized symbols to represent different actions or steps in an algorithm.
2. Connectors: A flowchart uses connectors to show the flow of control between different steps or actions.
3. Annotation: A flowchart may include annotation or labels to provide additional information about the steps or actions being represented.
4. Clarity: A flowchart should be clear and easy to understand, with a logical flow of control.
5. Consistency: A flowchart should use consistent symbols and connectors throughout, to avoid confusion and make the flow of control easy to follow.