Concepts of Programming Languages ---- Chapter 5 Names, Bindings, and Scopes

Concepts of Programming Languages ---- Chapter 5 Names, Bindings, and Scopes

Name : Fandy Limardi
NIM : 1601210713
Lecture : Tri Djoko Wahjono, Ir., M.Sc. (D0206)
Assignment : Concept of programming languages ---- Chapter 5 Names, Bindings, and Scopes

Review Questions

1.       What are the design issues for names?

-          Are names case sensitive?

-          Are the special words of the language reserved words or keywords?

2.       What is the potential danger of case sensitive names?

Case sensitive violates the design principle that language constructs that look similar should have similar meanings. But in language whose variable names are case-sensitive, although for example rose and Rose look similar, there is no connection between them.

3.       In what way are reserved words better than keywords

As a language design choice, reserved words are better than keywords because the ability to redefine keywords can be confusing.

4.       Which category of C++ reference variables is always aliases?

Union type category of C++ reference variables is always aliases.

5.       What is the referencing environment of a statement?

The referencing environment of a statement is the collection of all variables that are visible in the statement.

6.       What is a block?

Block is a section of code which the section is entered and deallocated when the section is exited.

7.       What are the advantages and disadvantages of dynamic scoping?

Adavantages :

-          Easier to read

-          More reliable

-          Execute faster than equivalent programs in dynamic scoped languages.

Disadvantages :

-          There is no way to protect local variables from this accessibility.

-          Inability to type check references to nonlocals statically.

-          Dynamic scooping makes programs much more difficult to read, because the calling sequence of subprograms must be known to determine the meaning of references to nonlocal variables.

8.       What are the advantages of named constants?

The advantages of named constants are useful as aids to readability and program reliability.

Problem Set

1.       Decide which of the following identifier names in valid in C language. Support your decision

_Student

Int

Student

123Student

Student123

Answer : _Student, Student,Student123

2.       What is l-value? Write a statement in C language which gives the compile time error “l-value required”

The address of a variable is sometimes called its I-value. The statement in C language which gives the compile time error is scanf(“%d”, value);

3.       Why is the type declaration of a variable necessary? What is the value range of the int type variable in Java?

Because the program have to know what data type of a variable and the value of the variable. The value range of the int type variable in Java is around -2147483648 to 2147483647.

4.       Assume the following JavaScript program was interpreted using static-scoping rules. What value of x is displayed in function sub1?
Under dynamic-scoping rules, what value of x is displayed in sub1?

               var x;

               function sub1() {

               document.write("X="+ x + " <br />");

               }

               function sub2() {

               var x;

                x=10

               sub1();

               }

               x=5;

               sub2();

   Answer : Static scope: x=5 Dynamic scoping: x=10.