Problem Solving via Programs
                                                                                                      • A computer is a tool that solves problems by 
                                                                                                         means of programs written in PLs.
                            Programming Paradigms (Styles)                                            • A typical program development process:
                                                                                                         – Requirement analysis (specification)
                                                                                                         – Design a solution
                                                                                                         – Implement as programs in a PL
                                                                                                         – Verification/validation
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                                 Paradigms and Programs                                                          What Is a Programming 
                                                                                                                           Paradigm?
                                                                                                      • A collection of conceptual patterns that 
                                             Problems                                                    together mold the program design process and 
                          Paradigms                        Design a solution                             ultimately determine a program’s structure.
                                              Solutions                                                  – How we think about and formulate solutions
                             PLs                           Implement as programs                         – The form of programs
                                              Programs     in a PL
                                              Computer
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                           Programming Paradigms and PLs                                                        Programming Paradigms
                        • Relationship between PPs and PLs:                                           • Operational Approach
                           – Once we visualize a solution via a paradigm’s                               – Describes step-by-step how to construct a solution.
                             conceptual pattern, we express it in a PL                                • Definitional (Declarative) Approach
                           – A PL that reflects a particular paradigm well, this                         – States properties about the solution. 
                             PL is said to support that paradigm                                      • Demonstrational Approach
                        • Does a PL support only one paradigm ?                                          – Demonstrates solutions (examples) to specific 
                           – No, typically it supports one paradigm very well.                              instances of simple problems.
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                                  Programming Paradigms                                                           Imperative Programming 
                                                                                                                              Paradigms
                        • Operational Approach                                                          • Characterized by an abstract model of a 
                            – Imperative (Procedural) Programming                                          computer that consists of a single large global 
                            – Object-Oriented Programming                                                  store.
                        • Definitional (Declarative) Approach (Paradigms)                               • The computer stores an encoded representation 
                            – Functional Programming                                                       of a computation and executes a sequence of 
                            – Logic Programming                                                            command or expressions that modifies the 
                        • Demonstrational Approach (Paradigms)                                             store.
                            – Program by example                                                        • Best represented by Von-Neumann style 
                            – Visual Programming                                                           computer.
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                            Imperative (Procedure-Oriented)                                                   Object-Oriented Programming 
                                               Thinking                                                                       Paradigms
                        • How to do IP?                                                                 • In IP, each procedure/function deals with the 
                            – Determine what data values will be required.                                 concrete representation of data values in a 
                            – Represent these data values by associating them                              single global store.
                              with storage locations.                                                   • In OOP, each procedure/function operates on 
                            – Derive a step-by-step sequence of transformation to                          abstract values, rather than on stored 
                              the store.                                                                   representation.
                            – The final state represents the result values                                  – Objects
                              (solution).
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                             Imperative vs. Object-Oriented                                                       Object-Oriented Thinking
                                            Programming
                                    P/F                                                                 • How to do OOP ?
                                                                                                            – Define suitable objects for the problem.
                                                                                                            – Use these objects to describe step-by-step sequence 
                                                                          Grouping                            of operations.
                                 Global
                                  store
                                   IP                         OOP
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                                 Functional Programming                                                     Function-Oriented Thinking
                                            Paradigms
                       • Based on the mathematical model of functions                               • How to do FP ?
                          and function composition.                                                     – Define functions (using function composition)
                           – No concepts of a storage location that can be                              – Use a function application
                             assigned or modified. (no variables, no commands)
                       • Referentially transparent
                           – Easier to understand program
                       • Functions treated as first class values
                           – No restriction of use
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                            Logic Programming Paradigms                                                       Logic-Oriented Thinking
                       • Based on the mathematical model of facts and                               • How to do LP ?
                          rules that allow deduction of other facts.                                    – Define facts
                           – A logic program = facts + rules                                            – Define rules
                                                                                                        – Use a query
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                          Parallel/Concurrent Programming                                              Parallel/Concurrent Programming
                                            Paradigms
                       • Cooperating parallel process                                               • How to use P/C P?
                           – asynchronous                                                               – Automatically detect parallelism in a sequential 
                       • Single process applied to many data                                              pgm.
                           – synchronous                                                                – Add mechanisms that describe parallelism..
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                                  Programming Paradigms
                                              Programming Paradigm
                            Operational           Definitional     Demonstrational
                           IP       OOP            FP      LP           EP
                                            Parallel/Concurrent Paradigm
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