Write a basic program on how to cook yam

Here is a basic recipe for cooking yam:

Ingredients:
- 1 medium-sized yam
- Water
- Salt (optional)
- Butter or oil (optional)

Instructions:
1. Wash the yam thoroughly under running water to remove any dirt or debris.
2. Peel the yam using a vegetable peeler or knife.
3. Cut the yam into small cubes or slices, depending on your preference.
4. Fill a pot with enough water to cover the yam pieces.
5. Add a pinch of salt to the water, if desired, to add flavor to the yam.
6. Bring the water to a boil over medium heat.
7. Carefully add the yam pieces to the boiling water.
8. Let the yam cook for about 15-20 minutes, or until they are tender when pierced with a fork.
9. Drain the water from the pot and return the yam pieces to the pot.
10. Add a knob of butter or a drizzle of oil to the yam, if desired, for added flavor and richness.
11. Toss the yam pieces in the butter or oil until they are coated evenly.
12. Serve the cooked yam as a side dish or as part of a main meal.

Enjoy your delicious yam!