Questions

When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it – for example, the parent may need to check the child’s exit status. To be able to get this information, the parent calls `wait()’; In the interval between the child terminating and the parent calling `wait()’, the child is said to be a `zombie’ (If you do `ps’, the child will have a `Z’ in its status field to indicate this.)

Excessive use of nitrate including manure may be responsible forthe presence of toxic substance in groundwater. Phosphate can also enter the groundwater via excessive use of fertilizers. High application rates of nitrogen containing fertilizers combined with the high-water solubility of nitrate, leads to increased runoff into surface water as well as leaching into groundwater, thereby causing groundwater pollution.

Only a fraction of the nitrogen-based fertilizers, is converted to produce and other plant matter. Nitrate pollution in groundwater comes from pit latrines, it can cause blue baby syndrome.