Final answer:
Shallow binding binds a subprogram to the most recent environment of the caller before it was passed, using the latest variable values. Deep binding binds the subprogram to the environment when it was defined, maintaining the original variable values regardless of subsequent changes.
Step-by-step explanation:
When discussing subprograms in programming languages, shallow and deep binding refer to how the environment of a subprogram is referenced when passed as parameters. Shallow binding means that the environment is bound to the most recent environment of the caller before the subprogram was passed. This means that the subprogram uses the variable values present at the very last moment before it gets passed as a parameter. On the other hand, deep binding means that the environment is bound to the original environment where the subprogram was defined, therefore the subprogram uses the variable values that were in effect at the time it was defined, regardless of any subsequent changes.
For example, if a variable x is defined in the main program and then a subprogram that references x is passed as a parameter to another subprogram, shallow binding would use the value of x at the time the subprogram is passed, whereas deep binding would use the value of x when it was first declared in the main program.