Note

Multi entry subprogram : Co routine

Return type : is not a parameter profile

Advantages of using keyword parameter : can appear in any order

Disadvantages of using keyword parameter : user have to know the name of the formal parameter

Value of default formal parameter in C++ is located at : the end

Most imperative have function and procedure. Language that does not have procedure : Pascal

Language below that have stack dynamic local variable : Java

Recursive subprogram is first designed in : Algol

Pass by copy is the other name for : pass by value-result

Implementation of I/O parameter model is : Pass by name, pass by reference, pass by value-result

Aliases that happen in pass by reference can be eliminated using : pass by name

Characteristic of pass by name is : flexible but slow

Overloaded subprogram is also called : ad hoc polymorphism

If a subprogram have a unique protocol, then it is called : overloaded subprogram

Side effect problem could be avoided using : in-out mode parameter

The only language that can return any type value is : Ada

The first language that use co-routine is : Simula 67

One of the characteristic of co-routine is : multi-entry

Late binding happen at : pass by name

Variable dynamically allocated : is NOT characteristic of subprogram on FORTRAN 77

Subprogram linkage included : sub program call and return

Activation record on FORTRAN 77 only have one instance because : no recursion

Two main methods to access non-local variable in static scope is : static chain and display

The pair that is used to show actual reference of non-local variable on static scope is : chain offset, local offset

Disadvantage of using static chain to access non-local variable is : the cost to point to variable and hard to estimate the variable cost.

Display : collection of static link that is stored in stack array

To refer to local variable : Display is as fast as static chain

When referring non-local variable, static chain is fasten then display : if the static away level is the same

Compare with deep access, shallow access is : much faster and less costly

Characteristic of dynamic chain is : fast access, fast call

2 different method that is used for passing parameter in language that is similar to Algol is : pass by value, pass by reference

Method that is used to implement block are : parameter-less subprogram and local allocation above ARI

Example of process abstraction are : subprogram, concurrency, and exception handlers

The main feature of ADT are : encapsulation and information hiding

Parametrized ADT in C++ is called : Template Class

Concept of Encapsulation is first implemented by : Simula 67

Function in C++ that is used to give initial value to a new object is : constructor

Simulator : is not an operation that have to be made by ADT designer

Instance on ADT is called : object

Additional feature that differentiate Ada 95 with ada 83 are : protected object and asynchronous communication

Key concept on data abstraction : information hiding

Object modularity : is not the advantages of information hiding

Language which construction did not include information hiding is : SIMULA 67

Encapsulation in Ada is called : Package

C++’s class and Ada’s package are encapsulation

Generic or parametrized ADT in C++ is called : Template

Task : is implicitly started

Data task communication is done through : parameters, message passing and shared non local

Language that use dynamic binding between exception and handler is : PL/I

The first person to suggest the usage of static binding between exception and handler is : J.B. Goodenough

Exception in C++ is raised explicitly through : Throw [expression]

Language that didn’t provide build-in exception is  : c++

Handler on PL/I format :

ON condition [snap]

begin

…

end

Exception handling first developed in language : PL/I

Scope on C++ handle is specified by : Try construct

Language which design exception is considered weird because it doen’t have a name is : C++

Exception handler usually local on the code where the exception handling appear so it does not need 

parameter. This type didn’t happen in language : Ada, C++, and Java

Exception handling in C++ is NOT designed by : PL/I

Exception handling in C++ is different with Ada in : There exist built in exception and no named user defined exception

Language that force the user designed exception in form of class is : Java

The syntax throw new myException[ ] : is Java

All handler in C++ have the same name, Catch. This case is known as : overloaded name

Exception that is often ignored by user program is : throw able exception

Exception that is not concern with compiler is : unthrowable exception

Language that check array subscript error range are : Ada and Java

Exception handling in C++ is similar to Ada in : Static binding and spread onto function caller

The term monitor is first used by : C.A.J. Hoare

Concurrent Pascal is Wirth Pascal with extra feature except : guard

Instance on monitor is created using : Init statement

Features that is provided by monitor so cooperation synchronization between process happen is : semaphore queue

Two basic characteristic that is provided by the language with concurrency is : mutually exclusive access, competition among task

For distributed system, the best model for concurrency is : Message passing

Category of concurrency are : physical, logical, quasi concurrency

Concurrency can happen at these level : Instruction, unit, program

Co-routine = quasi concurrency

Binary semaphore is : access

Programming Language Concept (16)

Book : Concept of Programming Language
Page 759
Review Question
1. What are the three primary uses of symbolic logic in formal logic ?
- to express propositions, to express the relationships between propositions, and to
describe how new propositions can be inferred from other propositions that
are assumed to be true.

2. What are the two parts of a compound term ?
- functor and and ordered list of of parameters

3. What are the two modes in which a proposition can be stated ?
- one in which a proposition is defined to be true and one in which that the proposition is something to be determined.

4. What is general form of a proposition in clausal form ?
-B1 U B2 U . . . U Bn C A1 n A2 n . . . n Am

5. What are antecedents ? Consequents ?
- Antecedents are right side of a clausal form proposition. Consequent is left side of a clausal form propositions

6. Give general definitions of resolution and unification
- Resolution : inference rule that allows inferred propositions to be computed from given propositions, thus providing a method with potential application to automatic theorem proving.
Unification : Process of determining useful values for variables.

7. What are the forms of Horn clauses ?
- a. Have a single atomic proposition on the left side
b. empty left side.

9. What does it mean for a language to be nonprocedural ?
- Language in which the programs do not exactly state how a result is to be computed but rather describe the form of the result.


Page 760
Problem Set
1. “All predicate calculus propositions can be algorithmically converted to clausal form”. Is this statement true or false ? Explain.
- True.

8. Critically comment on the following statement : “ Logic programs are nonprocedural”
- It is true, because logical programs use lots of different processes based on its conditions. If a certain logical requirement is true, then a program will execute the corresponding process, instead of procedurally executing the statements.

9. From a book on Prolog, learn and write a description of a monkey-banana prolem. Why does Prolog allow this problem to exist in its implementation ?
- The problem is defined as this : a monkey is in a room. Suspended from the ceiling is a bunch of bananas, beyond the monkey’s reach. However, in the room there are also a chair and a stick. The ceiling is just the right height so that a monkey standing on a chair could knock the bananas down with the stick. The monkey knows how to move around, carry other things around, reach for the bananas, and wave a stick in the air. What is the best sequence of actions for the monkey?
It exists to create a variation in output of Prolog. As Prolog is an AI programming language, a variation might be needed in AI output to make them respond relevant to the situation.

Programming Language Concept (15)

Book : Concept of Programming Language
Page 721
Review Question
2.   A lambda expression specifies the parameters and the mapping of a function.

3.   Atoms and lists were parts of the original LISP.

6.   Simple list is a list which membership of a given atom in a given list that does not include sublists.

7.   REPL stand for read-evaluate-print loop.

8.   Three parameters to IF are: a predicate expression, a then expression, and an else expression.

18.   A function is tail recursive if its recursive call is the last operation in the function. This means that the return value of the recursive call is the return value of the nonrecursive call to the function. It is important to specify repetition to be tail recursive because it is more efficient(increase the efficiency).

22.  During reader phase of a common LISP language processor,  There is a special kind of macro, named reader macros or read macros, that are expanded.  A reader macro expands a specific character into a string of LISP code. For example, the apostrophe in LISP is a read macro that expands to a call to QUOTE.

24.  What is stored in an ML evaluation environment?
A table called the evaluation environment stores the names of all implicitly and explicitly declared identifiers in a program, along with their types. This is like a run-time symbol table.

29.  Curried function let new functions can be constructed from them by partial evaluation.

30.  Partial evaluation means that the function is evaluated with actual parameters for one or more of the leftmost formal parameters.

33.  Explain the process of currying.
The process of currying replaces a function with more than one parameter with a function with one parameter that returns a function that takes the other parameters of the initial function.

35.   A language is nonstrict if it does not have the strict requirement.

43.  What is the syntax of a lambda expression in F#?
The following lambda expression illustrates their syntax:
(fun a b −> a / b)

Page 723
Problem Set

2.  Give the general form of function declaration in ML.
Function declarations in ML appear in the general form
fun function_name( formal parameters ) = expression;

8.   How is the functional operator pipeline ( | > )used in F#?
The pipeline operator is a binary operator that sends the value of its left operand, which is an expression, to the last parameter of the function call, which is the right operand. It is used to chain together function calls while flowing the data being processed to each call.
Consider the following example code, which uses the high-order functions filter and map:
let myNums = [1; 2; 3; 4; 5]
let evensTimesFive = myNums
|> List.filter (fun n −> n % 2 = 0)

10.  What does  the following Scheme function do?
(define ( x lis)
(cond
(( null? lis) 0 )
(( not(list? (car lis)))
(cond
((eq? (car lis) #f) (x (cdr lis)))
(else (+1 (x (cdr lis))))))
(else (+ (x (car lis))  (x (cdr lis))))
x returns the number of non-#f atoms in the given list
|> List.map (fun n −> 5 * n)

Programming Language Concept (14)

Book : Concept of Programming Language

Page 665
Review Question
2.   An exception is raised when its associated event occurs.
 
3.   The advantages of having support for exception handling builtin to language:
• First, without exception handling, the code required to detect error conditions can considerably clutter a program.
• Another advantage of language support for exception handling results from exception propagation. Exception propagation allows an exception raised in one program unit to be handled in some other unit in its dynamic or static ancestry.
• A language that supports exception handling encourages its users to consider all of the events that could occur during program execution and how they can be handled. This approach is far better than not considering such possibilities and simply hoping nothing will go wrong.
 
9.   An exception handler in Ada can occur in either a  subprogram body, a package body, a task, or a block
 
10.  There are four exceptions that are defined in the default package, Standard:
Constraint_aError
Program_Error
Storage_Error
Tasking_Error
 
12.   The suppress pragma is used to disable certain run-time checks that are parts of the built-in exceptions in Ada.
 
14. The name of all C++ exception handlers is Try clause.
 
15.  The exception out_of_range is thrown by library container classes.
 
16.  The exception overflow_error is thrown by math library functions.
 
32.  Event-driven programming is a programming where parts of the program are executed at completely unpredictable times, often triggered by user interactions with the executing program.
 
33.   The JFrame class defines the data and methods that are needed for frames. So, a class that uses a frame can be a subclass of JFrame. A JFrame has several layers, called panes.
 
Page 667  
Problem Set  
1.   What mechanism did early programming languages provide to detect or attempt to deal with errors?
Early programming languages were designed and implemented in such a way that the user program could neither detect nor attempt to deal with such errors. In these languages, the occurrence of such an error simply causes the program to be terminated and control to be transferred to the operating system.
 
2.   Describe the approach for the detection of subscript range errors used in C and Java.
In C subscript ranges are not checked. Java compilers usually generate code to check the correctness of every subscript expression. If any exception generates, then an unchecked exception is thrown.
 
4.   What are the different approaches to handle checked exception in Java?
In Java there are basically two types of exceptions: Checked exceptions and unchecked exceptions.
Checked exceptions must be explicitly caught or propagated as described in Basic try-catch-finally Exception Handling. Unchecked exceptions do not have this requirement. They don’t have to be caught or declared thrown.
Checked exceptions in Java extend the java.lang.Exception class. Unchecked exceptions extend the java.lang.RuntimeException.
 
14.  Summarize the arguments in favor of the termination and resumption models of continuation.
The resumption model is useful when the exception is only an unusual condition, rather than an error. The termination model is useful when the exception is an error and it is highly unlikely that the error can be corrected so that execution could continue in some useful way.

Programming Language Concept (13)

Book : Concept of Programming Language

 

Page 625
Review Question
 1.   Three possible levels of concurrency in programs:
• instruction level (executing two or more machine instructions simultaneously),
• statement level (executing two or more high-level language statements simultaneously)
• unit level (executing two or more subprogram units simultaneously)

2.   In an SIMD computer, each processor has its own local memory. One processor controls the operation of the other processors. Because all of the processors, except the controller, execute the same instruction at the same time, no synchronization is required in the software.

5.   Unit-level concurrency is best supported by MIMD computers.

6.   Vector processor have groups of registers that store the operands of a vector operation in which
the same instruction is executed on the whole group of operands simultaneously.

7.   Physical concurrency is several program units from the same program that literally execute simultaneously.
Logical concurrency is multiple processors providing actual concurrency, when in fact the actual execution of programs is taking place in interleaved fashion on a single processor.

8.   A scheduler manages the sharing of processors among the tasks. If there were never any interruptions and tasks all had the same priority, the scheduler could simply give each task a time slice, such as 0.1 second, and when a task’s turn came, the scheduler could let it execute on a processor for that amount of time.

16.   A task descriptor is a data structure that stores all of the relevant information about the execution state 
of a task.

18.   The purpose of a task-ready queue is to be storage of tasks that are ready to run.

21.   A binary semaphore is  a semaphore that requires only a binary-valued counter.
A counting semaphore is a synchronization object that can have an arbitrarily large number of states.

30.   Ada terminate clause, when selected, means that the task is finished with its job but is not yet terminated. Task termination is discussed later in this section.

34.   Sleep method in Java blocks the the thread.

35.   Yield method in Java surrenders the processor voluntarily as a request from the running thread.

36.  The join method in Java is used to force a method to delay its execution until the run method of another thread has completed its execution.

55.   Concurrent ML is an extension to ML that includes a fform of threads and a form of synchronous message passing to support concurrency.

56.  The use of spawn primitive of CML is to take the function as its parameter and to create a thread.

57.   The use of subprograms BeginInvoke and Endinvoke in F# is to call threads asynchronously.

60.   What is the type of an F# heap-allocated mutatable variable?
A mutable heap-allocated variable is of type ref

63.  The FORALL statement of High-Performance Fortran is to specifies a sequence of assignment statements that may be executed concurrently.

Page 627
Review Question
1. Explain clearly why a race condition can create problems for a system.
Race condition can create problems for a system, because two or more tasks are racing to use the shared resource and the behavior of the program depends on which task arrives first (and wins the race).

2.   The different ways to handle deadlock:
- Ignoring deadlock
- Detection
- Prevention
- Avoidance

3.    Busy waiting is a method whereby a task waits for a given event by continuously checking for that event to occur. What is the main problem with this approach?
Busy-waiting or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input or a lock is available. Spinning can also be used to generate an arbitrary time delay, a technique that was necessary on systems that lacked a method of waiting a specific length of time. Processor speeds vary greatly from computer to computer, especially as some processors are designed to dynamically adjust speed based on external factors, such as the load on the operating system. Busy waiting may loop forever and it may cause a computer freezing.

Programming Language Concept (12)

Book : Concept of Programming Language

Page 570
Review Question
2.   The problems associated with programming using abstract data types are:
• In nearly all cases, the features and capabilities of the existing type are not quite right for the new use.
• The type definitions are all independent and are at the same level.
 
3.   The advantage of inheritance is inheritance offers a solution to both the modification problem posed by abstract data type reuse and the program organization problem. If a new abstract data type can inherit the data and functionality of some existing type, and is also allowed to modify some of those entities and add new entities, reuse is greatly facilitated without requiring changes to the reused abstract data type.
 
4.   Message protocol is the entire collection of methods of an object.
 
6. Describe a situation where dynamic binding is a great advantage over its absence.
- There is a base class, A, that defines a method draw that draws some figure associated with the base class. A second class, B, is defined as a subclass of A. Objects of this new class also need a draw method that is like that provided by A but a bit different. With overriding, we can directly modify B’s draw function. But without it, we either make a specific function in A for B and inherit it.
 
7.   Dynamic dispatch is the third characteristic (after abstract data types and inheritance) of object-oriented programming language which is a kind of polymorhphism provided by the dynamic binding of messages to method definitions.
 
8.   An abstract method is an implemented method which all of descendant class should have and it is included in Building.
An abstract class is  a class that includes at least one abstract method.
 
10.  An inner class is  a nonstatic class that is nested directly in another class.
 
12.  All Smalltalk objects are allocated from the heap and are referenced through reference variables, which are implicitly dereferenced.
 
15.  Smalltalk supports single inheritance; it does not allow multiple inheritance.
 
19.  C++ heap-allocated objects are deallocated using destructor.
 
29.  No Objective-C doesn’t support it. Objective-C only supports single inheritance.
 
31.  The root class in Objective-C is called NSObject
 
38.  Boxing is primitive values in Java 5.0+ which is implicitly coerced when they are put in object context. This coercion converts the primitive value to an object of the wrapper class of the primitive value’s type.
 
49.  Access control in Ruby is different for data than it is for methods. All instance data has private access by default, and that cannot be changed. If external access to an instance variable is required, accessor methods must be defined.
 
Page 572 
Problem Set  
 
2.    In what ways can “compatible “ be defined for the relationship between an overridden method and the overriding method?
Every overriding method must have the same number of parameters as the overridden method and the types of the parameters and the return type must be compatible with those of the parent class.

3.   Compare the inheritance of C++ and Java.
• In Java, all objects are Inherited, either directly or indirectly. While in C++ a class can be defined to stand on its own without an ancestor.
•  The meaning of protected member access specifier is somewhat different in Java. In Java, protected members of a class “A” are accessible in other class “B” of same package, even if B doesn’t inherit from A (they both have to be in the same package).
•  Java uses extends keyword for inheritence. Unlike C++, Java doesn’t provide an inheritance specifier like public, protected or private. Therefore, we cannot change the protection level of members of base class in Java, if some data member is public or protected in base class then it remains public or protected in derived class. Like C++, private members of base class are not accessible in derived class. Unlike C++, in Java, we don’t have to remember those rules of inheritance which are combination of base class access specifier and inheritance specifier.
 
5.    Compare abstract class and interface in Java.
• First and major difference between abstract class and interface is that, abstract class is a class while interface is a interface, means by extending abstract class you can not extend another class because Java does not support multiple inheritance but you can implement multiple inheritance in Java.
• Second difference between interface and abstract class in Java is that you can not create non abstract method in interface, every method in interface is by default abstract, but you can create non abstract method in abstract class. Even a class which doesn’t contain any abstract method can be abstract by using abstract keyword.
• Third difference between abstract class and interface in Java is that abstract class are slightly faster than interface because interface involves a search before calling any overridden method in Java. This is not a significant difference in most of cases but if you are writing a time critical application than you may not want to leave any stone unturned.
• Fourth difference between abstract class vs interface in Java is that, interface are better suited for Type declaration and abstract class is more suited for code reuse and evolution perspective.
• Another notable difference between interface and abstract class is that when you add a new method in existing interface it breaks all its implementation and you need to provide an implementation in all clients which is not good. By using abstract class you can provide default implementation in super class.
 
7.   What is one programming situation where multiple inheritance has a significant disadvantage over interfaces?
A situation when there are two classes derived from a common parent and those two derived class has one child.
 
9.   Give an example of inheritance in C++, where a subclass overrides the superclass methods.
class Enemy{
protected:
int Hp;
public:
void attack(){
cout<<”Enemy Attacks using GUN!!”<<endl;
}
};
class BossEnemy: public Enemy{
public:
void attack(){
cout<<”Boss Enemy attacks using MAGIC!!”<<endl;
}
};
 
10.  Explain one advantage of inheritance.
One of the key benefits of inheritance is to minimize the amount of duplicate code in an application by sharing common  code amongst several subclasses. Where equivalent code exists in two related classes, the hierarchy can usually be  refactored to move the common code up to a mutual superclass. This also tends to result in a better organization of  code and smaller, simpler compilation units.
 
17.  What are the different options for object destruction in Java?
There is no explicit deallocation operator. A finalize method is implicitly called when the garbage collector is about to reclaim the storage occupied by the object.

Programming Language Concept (11)

Book : Concept of Programming Language

Page 519
Review Question
1. What are the two kinds of abstractions in programming languages ?
- Process Abstraction and Data Abstraction

2. Define abstract data type .
- A data structure in the form of a record, but which includes subprograms that manipulate its data.

3. What are the advantages of the two parts of the definition of abstract data type ?
- Increased reliability, Reduces range of code and number of variables which a programmer must be aware when writing / reading part of program. Make name conflict less likely to happen

5. What are the language design issues for abstract data types ?
- ADTs must have a function that allows a user to modify a value inside that data type. Although the method is public, the value itself must be private.

10. What is the use of the Ada with clause ?
- To make the names defined in external packages visible

11. What is the use of the Ada use clause ?
- To eliminate the need for explicit qualification of the references to entities from the named package.

12. What is the fundamental difference between a C++ class and an Ada package ?
- Class must be accessed from an instance of itself while package can be accessed directly.

13. From where are C++ objects allocated ?
- From heap

15. What is the purpose of a C++ destructor ?
- To deallocate heap space the object used.

16. What are the legal return types of a destructor ?
- destructor has no return type

21. What are initializers in Objective-C?
- Constructors that must be explicitly called.

26. Why does Java not have destructors ?
- Because Java has its own implicit garbage collection.

Page 520
Problem Set  
2. Suppose someone designed a stack abstract data type in which the function top returned an access path (or pointer ) rather than returning a copy of the top element. This is not a true data abstraction. Why ? Give an example that illustrates the problem.
- The problem with this is that the user is given access to the stack through the returned value of the “top” function. For example, if p is a pointer to objects of the type stored in the stack, we could have:
p = top(stack1);
*p = 42;
These statements access the stack directly, which violates the principle of a data abstraction.

4. What are the advantages of the nonpointer concept in Java ?
- Variable Access are absolutely defined by the programmer
- No memory leak (i.e. dangling pointers, nameless variables etc)

9. What happens if the constructor is absent in Java and C++ ?
- The compiler will automatically make a default one

11. Why is the destructor of C# rarely used ?
- Because C# has its own garbage collection method , just like Java

Programming Language Concept (10)

Book : Concept of Programming Language

Page 466
Review Question
1. What is the definition used in this chapter for “simple” subprograms ?
-Subprograms cannot be nested and all local variables are static.

2. Which of the caller of callee saves execution status information ?
-Either can save the execution status

3. What must be stored for the linkage to a subprogram ?
- Execution status information

4. What is the task of a linker ?
- find files that contain the translated subprograms referenced in that program and load them into memory, set target addresses of all calls to those subprograms in the main program to the entry addresses of those subprograms.

8. What kind of machines often use registers to pass parameters ?
- RISC Machines

10. Define static chain, static_depth, nesting_depth,and chain_offset.
-static chain : a chain of static links that connect certain activation record instances in the stack.
-static_depth : integer associated with a static scope that indicates how deeply it is nested in the outermost scope.
-nesting_depth : difference between static_depth of a subprogram containing reference to x and the static_depth of a subprogram containing the declaration of x.
-chain_offset : number of links to the correct activation record instance

12. How are references to variables represented in the static-chain method ?
-It is represented by static_depth.


Page 467
Problem Set  
1. Show the stack with all activation record instances, including static and dynamic chains, when execution reaches position 1 in the following skeletal program. Assume Bigsub is at level 1.
(page 487)

      -      +--------------------------------------------+ <------ top
     /       !       Dynamic link                     ! --+>----\
    /        !----------------------------------------+---!     !
   B         !       Static link                      ! -----\  !
    \        !----------------------------------------+---!  !  !
     \       !       Return (to C)                    !   !  !  !
      -      !----------------------------------------+---!<-+--/
     /       !       Dynamic link                     ! --+>-!
    /        !----------------------------------------+---!  !
   C         !       Static link                      ! --+>-!
    \        !----------------------------------------+---!  !
     \       !       Return (to A)                    !   !  !
      -      !----------------------------------------+---!<-/
     /       !       Dynamic link                     ! --+>------\
    /        !----------------------------------------+---!       !
   A         !       Static link                      ! --+>------!
    \        !----------------------------------------+---!       !
     \       !       Return (to BIGSUB)               !   !       !
      -      !----------------------------------------+---!<------/
BIGSUB       !       Local variables                  !   !
             +----------------------------------------+---+

6. Although local variables in Java methods are dynamically allocated at the beginning of each activation, under what circumstances could the value of a local variable in a particular activation retain the value of previous activation ?
- If the variable is declared as static. Static modifier is a modifier that makes a variable history – sensitive.

7. It is stated in this chapter that when nonlocal variables are accessed in a dynamic-scoped language using the dynamic chain, variable names must be stored in the activation records with the values. If this were actually done, every nonlocal access would require a sequence of costly string comparisons on names. Design an alternative to these string comparisons that would be faster.

- Using approach that uses an auxiliary data structure called a display. Or, to write variable names as integers. These integers act like an array. So when the activation happens, the comparisons will be faster.

9. The static-chain method could be expanded slightly by using two static links in each activation record instance where the second points to the static grandparent activation record instance. How would this approach affect the time required for subprogram linkage and nonlocal references ?
-Including two static links would reduce the access time to nonlocals that are defined in scopes two steps away to be equal to that for nonlocals that are one step away. Overall, because most nonlocal references are relatively close, this could significantly increase the execution efficiency of many programs.

Programming Language Concept (9)

Book : Concept of Programming Language

Page 436
Review Question
1. What are three general characteristics of subprograms ?
- each subprograms has a single entry point
- the calling program unit is suspended during the execution of the called subprogram, which implies that there is only one subprogram in execution at any given time.
- Control always returns to the caller when the subprogram execution terminates.

2. What does it mean for a subprogram to be active ?
- if it has been called and started execution but the execution is not completed yet.

3. What is given in the header of a subprogram ?
- specifies that the following syntactic unit is a subprogram definition of some particular kind, provides name of the subprogram, optionally specifies a list of parameters

4. What characteristics of Python subprograms sets them apart from those of other languages ?
- function def statements are executable

5. What languages allow a variable number of parameters ?
- C,C++,Perl JavaScript, and Lua

6. What is a Ruby array formal parameter ?
- Substitute of keyword parameter which Ruby does not support

7. What is a parameter profile ? What is a subprogram protocol ?
- Parameter profile contains number, order and types of its formal parameter. Subprogram Protocol is the parameter profile and the return value if it is a function.

8. What are formal parameters ? What are actual parameters ?
- formal parameters are parameters in the subprogram header. Actual parameters are a list of parameters included in subprogram call statements

9. What are the advantages and disadvantages of keyword parameters ?
- The advantage is they can appear in any order in the actual parameter list. The disadvantage is the user must know the names of formal parameters.

10 . What are the differences between a function and a procedure ?
- Functions return values while procedure does not .
- Procedure defines new statements, while function define new user-defined operators.
Problem Set

Page 438
Problem Set 
1. What are arguments for and against a user program building additional definitions for existing operators, as can be done in Python and C++? Do you think such user-defined operator overloading is good or bad ? Support your answer.
- It is good, as long as the user knows what he or she is doing. C++ default operators are only working for default data types. As users can make their own datatypes, custom operators are also needed.

3. Argue in support of the templated functions of C++. How is it different from the templated functions of other languages ?
- It is different as C++ differentiates function based on overloading. It is not practical to make multiple function overloading in regard to writability and readability. Instead, creating a template allows a function to receive any datatype as long as the variation is based on the formal parameter definition.

5. Consider the following program written in C syntax :
(page 458)
For each of the following parameter-passing methods, what are all of the values of the variables value and list after each of the three calls to swap ?
a. Passed by Value
-value =1 , list[5] = {2,4,6,8,10}
b. Passed by reference
-value =6, list[5] ={4,1,2,8,10}
c. Passed by value-result
-value =6, list[5] ={4,1,2,8,10}

7. Consider the following program written in C syntax :
(page 459)
For each of the following parameter-passing methods, what are the values of the list array after execution ?
a. Passed by value
- list[2] = {3,5}
b. Passed by reference
- list[2] = {6,10 }
c. Passed by value-result
- list[2] = {6,10 }