1. High-Level Programming Languages
Chapter 8
High-Level Programming Languages

2. Chapter Goals
Describe the translation process and distinguish between assembly, compilation, interpretation, and execution
Name four distinct programming paradigms and name a language characteristic of each
Describe the following constructs: stream input and output, selection, looping, and subprograms

3. Chapter Goals
Construct Boolean expressions and describe how they are used to alter the flow of control of an algorithm
Define the concepts of a data type and strong typing
Explain the concept of a parameter and distinguish between value and reference parameters

4. Chapter Goals Describe two composite data-structuring mechanisms
Name, describe, and give examples of the three essential ingredients of an object-oriented language

5. Compilers High-level language
A language that provides a richer (more English like) set of instructions
Compiler
A program that translates a high-level language program into machine code

6. Compilers How does this differ from the assembly process?
Figure 8.1 Compilation process

7. Interpreters Interpreter
A translating program that translates and executes the statements in sequence
Assembler or compiler produce machine code as output, which is then executed in a separate step
An interpreter translates a statement and then immediately executes the statement
Interpreters can be viewed as simulators

8. Java Introduced in 1996 and became instantly popular
Portability was of primary importance
Java is compiled into a standard machine language called Bytecode
A software interpreter called the JVM (Java Virtual Machine) takes the Bytecode program and executes it

9. Do you understand the difference?
Portability
Portability
The ability of a program to be run on different machines
Compiler portability
A program in a standardized language can be compiled
and run on any machine that has the appropriate compiler
Bytecode portability
A program translated into Bytecode can be run on
any machine that has a JVM
Do you understand the difference?

10. Portability
Figure Portability provided by standardized languages versus interpretation by Bytecode

11. Portability
Figure Portability provided by standardized languages versus interpretation by Bytecode

12. Programming Language Paradigms
Imperative or procedural model
Program describes the processing
FORTRAN, COBOL, BASIC, C, Pascal, Ada, and C++
Functional model
Program is written terms of mathematical functions
LISP, Scheme (a derivative of LISP), and ML

13. Programming Language Paradigms
Logic model
Program consists of facts about objects and rules that question the relationships among facts
PROLOG
Object-oriented model
Program consists of a set of objects and the interactions among the objects
Smalltalk and Simula
C++ is as an imperative language with some object-oriented features
Java is an object-oriented language with some imperative features

14. Programming Language Paradigms
We examine procedural and object-oriented languages in the rest of this chapter by looking at the functionality provided in these languages
We give examples in different languages to show how syntax used to provide the functionality

15. Functionality of Imperative Languages
Sequence
Executing statements in sequence until an instruction is encountered that changes this sequencing
Selection
Deciding which action to take
Iteration (looping)
Repeating an action
Do these concepts sound familiar?
Let's review them.

16. Boolean Expressions Boolean expression
A sequence of identifiers, separated by compatible operators, that evaluates to true or false
A Boolean expression can be
A Boolean variable
An arithmetic expression followed by a relational operator followed by an arithmetic expression
A Boolean expression followed by a Boolean operator followed by a Boolean expression

17. Boolean Expressions Variable
A location in memory that is referenced by an identifier that contains a data value
Thus, a Boolean variable is a location in memory that can contain either true or false

18. Remember the relational operators?
Boolean Expressions
Remember the relational operators?
List them!

19. Strong Typing Data type
A description of the set of values and the basic set of operations that can be applied to values of the type
Strong typing
The requirement that only a value of the proper type can be stored into a variable

20. Data Types Integer numbers Real numbers Characters Boolean values
Strings
Give examples of
each

21. Integers What determines the range of an integer value?
Is the range of an integer value the same in all languages?
What operations can be applied to integers?

22. Reals How are real values like integer values?
How do real values differ from integer values?

23. Characters Do you remember ASCII? Extended ASCII? UNICODE?
How many characters in Extended ASCII?
How many characters in UNICODE?
What does a relational operator between two characters mean?

24. Boolean and Strings What values can a Boolean variable be?
For what are Boolean expressions used?
What is a string?
What operations can be applied to strings?

25. Declarations Declaration
A statement that associates an identifier with a variable, an action, or some other entity within the language that can be given a name; the programmer can refer to that item by name
Reserved word
A word in a language that has special meaning
Case-sensitive
Uppercase and lowercase letters are considered the same

26. Declaration Example

27. Assignment statement Assignment statement
An action statement (not a declaration) that says to evaluate the expression on the right-hand side of the symbol and store that value into the place named on the left-hand side
Named constant
A location in memory, referenced by an identifier, that contains a data value that cannot be changed
Remember?

28. Input/Output Structures
Pseudocode algorithms used the expressions Read or Get and Write or Print
High-level languages view input data as a stream of characters divided into lines
Key to the processing
The data type determines how characters are to be converted to a bit pattern (input) and how a bit pattern is to be converted to characters (output)

29. Input/Output Structures
Read name, age, hourlyWage
name is a string;
age is an integer;
hourlyWage is a real
The data must be a string, an integer, and a
real in that order.

30. Control Structures Control structure
An instruction that determines the order in which other instructions in a program are executed
Can you name the ones we defined in the functionality of pseudocode?

31. Selection Statements
Figure 8.3 Flow of control of if statement

32. Selection Statements
The if statement allows the program to test the state of the program variables using a Boolean expression

33. Blocks
Note
the
symbols
used to
indicate
blocks
in each
language

34. Why does this work correctly?
Cascading Ifs
If (temperature > 90)
Write "Texas weather: wear shorts"
Else If (temperature > 50)
Write "A little chilly: wear a light jacket"
Else If (temperature > 32)
Write "Philadelphia weather: wear a heavy coat"
Else
Write "Stay inside"
Why does this work correctly?

35. Looping Statements
Figure Flow of control of while statement

36. Looping Statements A count-controlled loop Set sum to 0 Set count to 1
While (count <= limit)
Read number
Set sum to sum + number
Increment count
Write "Sum is " + sum
Why is it
called a
count-controlled
loop?

37. Looping Statements

38. Looping Statements An event-controlled loop Set sum to 0
Set allPositive to true
While (allPositive)
Read number
If (number > 0)
Set sum to sum + number
Else
Set allPositive to false
Write "Sum is " + sum
Why is it
called an
event-conrolled
loop?
What is the
event?

39. Subprogram Statements
We can give a section of code a name and use that name as a statement in another part of the program
When the name is encountered, the processing in the other part of the program halts while the named code is executed
Remember?

40. Subprogram Statements
What if the subprogram needs data from the calling unit?
Parameters
Identifiers listed in parentheses beside the subprogram declaration; sometimes called formal parameters
Arguments
Identifiers listed in parentheses on the subprogram call; sometimes called actual parameters

41. Subprogram Statements
Figure 8.5 Subprogram flow of control

42. Subprogram Statements
Figure 8.5 Subprogram flow of control

43. Subprogram Statements
Value parameter
A parameter that expects a copy of its argument to be passed by the calling unit
Reference parameter
A parameter that expects the address of its argument to be passed by the calling unit

44. Subprogram Statements
Think of arguments as being placed on a message board

45. Subprogram Statements

46. Recursion Recursion The ability of a subprogram to call itself
Base case
The case to which we have an answer
General case
The case that expresses the solution in terms of a call to itself with a smaller version of the problem

47. Recursion
For example, the factorial of a number is defined as the number times the product of all the numbers between itself and 0:
N! = N * (N  1)!
Base case
Factorial(0) = 1 (0! is 1)
General Case
Factorial(N) = N * Factorial(N-1)

48. Asynchronous Processing
Not synchronized with the program's action
Clicking has become a major form of input to the computer
Mouse clicking is not within the sequence of the program
A user can click a mouse at any time during the execution of a program

49. Composite Data Types Records
A named heterogeneous collection of items in which individual items are accessed by name
Arrays
A named homogeneous collection of items in which an individual item is accessed by its position (index) within the collection

50. Composite Data Types
Declare Record

51. Declare record variable
Composite Data Types
Declare record variable
Use record variable

52. Composite Data Types An Array
Figure 8.8 Array variable tenThings accessed from 0..9

53. Composite Data Types
Declare Array

54. Composite Data Types
Access an Array

55. Functionality of Object-Oriented Languages
Remember the definitions from Chapter 6?
Encapsulate
Object class
Object in problem-solving phase
Object in implementation phase
Class in implementation phase
Instantiate
Don't worry!
We'll review
these
concepts

56. Review Object class (problem-solving phase)
A description of a group of objects with similar properties and behaviors
Object (problem-solving phase)
An entity or thing that is relevant in the context of a problem
Instantiate
Create an object from a class

57. Review
Encapsulation
A language feature that enforces information hiding (second definition)
Class (implementation phase)
A language construct that is a pattern for an object and provides a mechanism for encapsulating the properties and actions of the object class
Object (implementation phase)
An instance of a class

58. Review Remember the pattern? From problem to general description
to class
definition to
program

59. Inheritance and Polymorphism
A construct that fosters reuse by allowing an application to take an already-tested class and derive a class from it that inherits the properties the application needs
Polymorphism
The ability of a language to have duplicate method names in an inheritance hierarchy and to apply the method that is appropriate for the object to which the method is applied

60. Inheritance and Polymorphism
Inheritance and polymorphism work together
How?
They combine to allow the programmer to build useful hierarchies of classes that can be put into a library to be reused in different applications