Photosynthesis is a major topic in all biology syllabuses, and this program aims to give factual information and help revision.

The menu offers four options: The Structure Of A Leaf, Adaptations Of A Leaf, Photosynthesis Experiments, and The Chemistry Of Photosynthesis.

In the section on leaf structure, the user has to label correctly the diagram of a transverse section of a leaf - but before starting he can choose to see a correctly-labelled diagram. When the labels have been entered, the computer does the marking and presents the option of trying again, going on to another section, or seeing the correctly-labelled diagram.

The leaf-adaptations option shows how leaves are designed to perform their functions efficiently. Again, the computer will demonstrate the various adaptations and the student is asked to match each adaptation to the role it plays - absorption of sunlight, transportation of gases and so on.

Before starting the third section the student should have seen demonstrations of several photosynthesis experiments. The computer demonstrates the apparatus used to test a leaf for starch; to show that light, carbon dioxide and chlorophyll are necessary for photosynthesis; and to show that oxygen is produced.

Each stage of an experiment is outlined in simple terms and illustrated with graphics, and then the result of the experiment is clearly stated. The user must match the apparatus to the right experiment.

The final section of Photosynthesis, The Chemistry of Photosynthesis, contains a very clear demonstration of the reaction equation, and again the computer tests and marks the student's knowledge.

Photosynthesis is a wide and complex topic, so this program doesn't attempt to cover every facet - but it's a very useful aid for O level.

Keyboard play: good Graphics: simple, but used to good effect; limited colour