Chapter 5: Names, Bindings, and Scopes

Review Questions:
1. What are the design issues for names?
   There are 2 primary design issues for names: first we have "are names case sensitive?", and second one is "are the special words of the language  reserved words or keywords?".

2. What is the potential danger of case-sensitive names?
   Writ ability and readability (because sometimes names that look alike are different thing).

3. In what way are reserved words better than keywords?
   Reserved words can be better than keywords because the ability to redefine keywords are confusing.

4. What is an alias?
   When more than one variable can be used to access the same memory location the variables are called alias.

5.  Which category of C++ reference variables is alwas aliases?
   Union types.

 Problem Set:
1. Which of the following identifier forms is most readable? Support your decision.

• SumOfSales
• sum_of_sales
• SUMOFSALES

   The most readable identifier is "sum_of_sales", because there are underscores as separator of the words in that variable.

2. Some programming languages are typeless. What are the obvious advantages and disadvantage of having no types in language?

   Advantages    : - It allows coders to write sloppy programs quickly.

   Disadvantages: - You are not in control of the data and variables, the compiler or interpreter is.

                            -  If you miss assigned variables, there's no way for the compiler to catch any of                                      your mistakes. It just "does what you said" even if it's wrong.

                            - Supporting programs in a typeless language is much more difficult. It often                                            couldn't recognize what the programmer actually want to do.

3. Write a simple assignment statement with one arithmetic operator in some language you know. For each component of the statement, list the various bindings that are required to determine the  semantics when the statement is executed. For each binding, indicate the binding time used for the language.

   int count; count = count + 5;

Possible types for count: set as language design time. 

Type of count: bound at compile time.

Set of possible values of count: bound at compiler design time. 

Value of count: bound at execution time with this statement.

Set of possible meanings for the operator symbol '''' in this statement: bound at compile time.

Internal repesentation of literal "5": bound at compiler design time.

4. Dynamic type binding is closely related to implicit heap-dynamic variables. Explain this relationship.

   Both are related to the assignment and the statement.

5. Describe a situation when a history-sensitive variable in subprogram is useful.

   It is useful when you have a subprogram to be recalled again after the subprogram itself had been exited. Then the function doesn't have the variable to be the parameter, but only to return it.