1. หลักการโปรแกรม เพื่อแก้ปัญหาโดยใช้คอมพิวเตอร์
อ.จรรยา สายนุ้ย
CS.313 ภาควิชาวิทยาการคอมพิวเตอร์

2. Outline Problem Solving Programming Principle Definition Strategies
Techniques
Tools
Approach
Programming Principle
Programming Language
Programming Design
Programming Paradigms

3. Problem Solving Definition
Problem Solving
The process of transforming the description of a problem into the solution of that problem by using own knowledge of the problem domain and be relying on the ability to select and use appropriate problem solving strategies, techniques and tools

4. Problem Domain
sciences : mathematics , statistics , chemistry , physics, biology
business : inventory , accounting
education : registration , evaluation
banking : ATM , loaning , report
others : restaurant , transportation , hotel , department store

5. Problem Solving Strategies
(Algorithm Design Techniques)
Divide and Conquer
Dynamic Programming
Greedy Algorithms
etc.

6. Problem Solving Techniques
Top-down Stepwise Refinement
Structured Programming
Modular Design
Bottom-up Approach
Recursion

7. Problem Solving Tools Pseudo Code Flowchart Programming Languages
Editor
Debugger

8. Problem Solving Approach
Software Development Method or Software Life Cycle
Use computers in problem solving consists of 6 steps :
Requirement Specification
Analysis
Design
Implementation
Testing And Verification
Documentation

9. Software Life Cycle Requirement Specification what the problem is
what is needed to solve
what the solution should provide
any constraints and special conditions to concern
depend on familiarity with the problem domain

10. Software Life Cycle Analysis Input Output Constraints/Conditions
Formulas

11. Software Life Cycle Design 3.1 Algorithm design 3.2 Data design
definition
requirement
strategy
techniques
3.2 Data design
Input/Output
Process
Types
Representation
Structure
manipulation

12. Software Life Cycle Algorithm Definition 3.1 Algorithm design
Algorithm : a method of solution described as a sequence of steps to be performed in a specific logical order.

13. Software Life Cycle Satisfied Requirements : 3.1 Algorithm design
Unambiguousness
Generality
Correctness
Finiteness

14. Software Life Cycle Representation Strategy 3.1 Algorithm design
Pseudocoding
Flowcharting
HIPO Chart

15. Software Life Cycle 3.1 Algorithm design Greedy Method
Techniques
Greedy Method
Divide and Conquer
Dynamic Programming
Backtracking Algorithms
etc.

16. Software Life Cycle 3.2 Data design Input/Output Process
Types : constant/variables ,global/local
Representation: number , text , etc.
Structure: array, file , queue , tree , etc.
Manipulation: operators , functions

17. Software Life Cycle Implementation or Coding Programming Languages
writability
readability
modifiability
reusability

18. Software Life Cycle Implementation or Coding
Important as designing skill
programming is the art of designing efficient algorithms to meet requirements
Programming errors
Debugging techniques
Strategies for defensive
Programming

19. Software Life Cycle Implementation or Coding Programming Errors
design errors
syntax/compilation errors
linker errors
run-time errors
warning diagnostic message

20. Software Life Cycle Implementation or Coding Debugging techniques
The ability to debug programs is another problem-solving skill that is as important as the ability to design programs
Debugging is the process of finding and correcting errors in computer programs

21. Software Life Cycle Implementation or Coding Debugging techniques
design errors
quite difficult to debug , no error message , incorrect output sometimes
incorrect formula , wrong program logic , inappropriate data type
careful review in analysis and design , use variety of testing data

22. Software Life Cycle Implementation or Coding Debugging techniques
syntax/compilation errors
Detect by compilers
Something missing / undeclared var.
Easy , just correct error sources
warning diagnostic message
Strange but can still proceed
Unreferenced var.
Get rid of causes or ignore

23. Software Life Cycle Implementation or Coding Debugging techniques
linker errors
Some errors prevent the linker to create the executable module
Function prototypes do not match their definitions
solution: correct prototypes

24. Software Life Cycle Implementation or Coding Debugging techniques
run-time/execution errors
while executing , difficult to debug, abnormal termination
divide by zero , type mismatch ,index is out of range, domain error
trace/step watch some variables’ value , error handling

25. Software Life Cycle Strategies for defensive correction : errors debug
Implementation or Coding
Strategies for defensive
correction : errors debug
defence : to prevent abnormal termination /errors
preparing to manage errors
if (a < o) { … }
using exception handler

26. Software Life Cycle Testing And Verification program verification
the process of ensuring that a program meets user requirements
one of the techniques that can be used for program verification is program testing

27. Software Life Cycle Testing And Verification program testing
the process of executing a program to demonstrate its correctness
testing methods
test data
testing modules : driver , stub
top-down testing
bottom-up testing
blackbox .vs. whitebox

28. Software Life Cycle: Example
Requirement Specification
เขียนโปรแกรมหาระยะทางระหว่างจุด 2 จุดคือ (x1 ,y1 ) และ (x2 ,y2 )
สูตรคือ

29. Software Life Cycle : Example
Analysis
Input: integer x1 , y1 , x2 และ y2
Output : float & positive value
Formulas :

30. Software Life Cycle: Example
Algorithm Design
Pseudocode
Read x1 , y1 , x2 , y2
dist = sqrt((x1 - x2)2 + (y1 - y2)2)
Write dist
end

31. Software Life Cycle: Example
Implementation or Coding
#include <stdio.h>
#include <math.h>
void main()
{ int x1, x2, y1, y2;
float dist;
scanf(“%d %d %d %d”, &x1, &y1, &x2, &y2);
dist = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
printf(“distance = %f\n”,dist); }

32. Software Life Cycle: Example
Testing And Verification
verifying: compile and debug
data test:
output: 5.0

33. Software Life Cycle Documentation System documentation
Program documentation
User documentation

34. Software Life Cycle Documentation System documentation Context Diagram
Dataflow Diagram
Database Design : E-R diagram , Relational model , Data dictionary
System modules/flowchart

35. Software Life Cycle Documentation Program documentation
Flowchart / Pseudocode
Program Listing
Sufficient in-program : comment , indentation

36. Software Life Cycle Documentation User documentation Interfaces
Input Examples
Output Examples
Error messages : causes & effect

37. Programming Principles
Programming Languages
Program Design
Programming Paradigms

38. Programming Languages
Why programming languages ?
to enable the user to enlist the help of a computer in solving problems in the domain of interest
to enable the user to bridge the gap between problem and machine domain

39. Program Design modular design stepwise refinement
top-down approach
bottom-up approach
stepwise refinement
structured programming
etc.

40. Programming paradigms
imperative paradigm
functional paradigm
logic paradigm
object-oriented paradigm

41. Practice make perfect