Programming Languages Overview PowerPoint Presentation

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Computer Science: An OverviewEleventh Edition by J. Glenn Brookshear Chapter 6:Programming Languages

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0-2 Chapter 6: Programming Languages 6.1 Historical Perspective 6.2 Traditional Programming Concepts 6.3 Procedural Units 6.4 Language Implementation 6.5 Object Oriented Programming 6.6 Programming Concurrent Activities 6.7 Declarative Programming

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0-3 Figure 6.1 Generations of programming languages

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0-4 Second-generation:Assembly language A mnemonic system for representing machine instructions Mnemonic names for op-codes Identifiers: Descriptive names for memory locations, chosen by the programmer

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0-5 Assembly Language Characteristics One-to-one correspondence between machine instructions and assembly instructions Programmer must think like the machine Inherently machine-dependent Converted to machine language by a program called an assembler

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0-6 Program Example Machine language156C166D505630CEC000 Assembly languageLD R5, PriceLD R6, ShipChargeADDI R0, R5 R6ST R0, TotalCostHLT

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0-7 Third Generation Language Uses high-level primitives Similar to our pseudocode in Chapter 5 Machine independent (mostly) Examples: FORTRAN, COBOL Each primitive corresponds to a sequence of machine language instructions Converted to machine language by a program called a compiler

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0-8 Figure 6.2 The evolution of programming paradigms

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0-9 Figure 6.3 A function for checkbook balancing constructed from simpler functions

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0-10 Figure 6.4 The composition of a typical imperative program or program unit

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0-11 Data Types Integer: Whole numbers Real (float): Numbers with fractions Character: Symbols Boolean: True/false

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0-12 Variable Declarations float Length, Width; int Price, Total, Tax; char Symbol;

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0-13 Figure 6.5 A two-dimensional array with two rows and nine columns

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0-14 Figure 6.6 The conceptual structure of the aggregate type Employee

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0-15 Figure 6.7 The for loop structure and its representation in C++, C#, and Java

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0-16 Procedural Units Local versus Global Variables Formal versus Actual Parameters Passing parameters by value versus reference Procedures versus Functions

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0-17 Figure 6.8 The flow of control involving a procedure

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0-18 Figure 6.9 The procedure ProjectPopulation written in the programming language C

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Figure 6.10 Executing the procedure Demo and passing parameters by value

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Figure 6.11 Executing the procedure Demo and passing parameters by reference

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0-21 Figure 6.12 The function CylinderVolume written in the programming language C

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0-22 Figure 6.13 The translation process

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0-23 Figure 6.14 A syntax diagram of our if-then-else pseudocode statement

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0-24 Figure 6.15 Syntax diagrams describing the structure of a simple algebraic expression

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0-25 Figure 6.16 The parse tree for the string x + y x z based on the syntax diagrams in Figure 6.17

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Figure 6.17 Two distinct parse trees for the statement if B1 then if B2 then S1 else S2

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0-27 Figure 6.18 An object-oriented approach to the translation process

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0-28 Objects and Classes Object: Active program unit containing both data and procedures Class: A template from which objects are constructed An object is called an instance of the class.

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0-29 Figure 6.19 The structure of a class describing a laser weapon in a computer game

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0-30 Components of an Object Instance Variable: Variable within an object Holds information within the object Method: Procedure within an object Describes the actions that the object can perform Constructor: Special method used to initialize a new object when it is first constructed

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0-31 Figure 6.21 A class with a constructor

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0-32 Object Integrity Encapsulation: A way of restricting access to the internal components of an object Private Public

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0-33 Figure 6.22 Our LaserClass definition using encapsulation as it would appear in a Java or C# program

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0-34 Additional Object-oriented Concepts Inheritance: Allows new classes to be defined in terms of previously defined classes Polymorphism: Allows method calls to be interpreted by the object that receives the call

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0-35 Programming Concurrent Activities Parallel (or concurrent) processing: simultaneous execution of multiple processes True concurrent processing requires multiple CPUs Can be simulated using time-sharing with a single CPU

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0-36 Figure 6.23 Spawning threads

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0-37 Controlling Access to Data Mutual Exclusion: A method for ensuring that data can be accessed by only one process at a time Monitor: A data item augmented with the ability to control access to itself

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0-38 Declarative Programming Resolution: Combining two or more statements to produce a new statement (that is a logical consequence of the originals). Example: (P OR Q) AND (R OR Q) resolves to (P OR R) Resolvent: A new statement deduced by resolution Clause form: A statement whose elementary components are connected by the Boolean operation OR Unification: Assigning a value to a variable so that two statements become “compatible.”

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0-39 Figure 6.24 Resolving the statements (P OR Q) and (R OR ¬Q) to produce (P OR R)

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0-40 Figure 6.25 Resolving the statements (P OR Q), (R OR ¬Q), ¬R, and ¬P

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0-41 Prolog Fact: A Prolog statement establishing a fact Consists of a single predicate Form: predicateName(arguments). Example: parent(bill, mary). Rule: A Prolog statement establishing a general rule Form: conclusion :- premise. :- means “if” Example: wise(X) :- old(X). Example: faster(X,Z) :- faster(X,Y), faster(Y,Z).