How many cylinders in a megabyte?

The term "cylinders" typically refers to a physical structure in hard disk drives, while "megabyte" is a unit of digital information. The number of cylinders in a megabyte cannot be directly calculated, as they measure different concepts. A cylinder's size in terms of data storage depends on the specific hard drive's geometry, including the number of tracks and sectors per track. Therefore, without additional context, the question isn't applicable.