Variables in the Bourne shell are more straightforward and homogeneous than in the C shell, and are treated more consistently.
There are no special variables that are propagated from shell to environment variables, and vice versa. There is only one command to set a normal variable, and one command to make any variable into an environment variable.
In sh, to set a key equal to a value, the syntax is:
Note that it is important that no spaces be included between the variable and the value to which it is being set.
To make a variable visible to the environment, it must be "'exported". The shell builtin export is designed for this task.