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Programming Fundamentals

and Methodology

COMP104: Introduction

Dr. Brian MakDr. Pedro Sander

Dr. Zhen Zhou

Department of Computer Science & Engineering

The Hong Kong University of Science and TechnologyHong Kong SAR, China

Fall 2007

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.1

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Part I

Computer, Computer Program, and ProgrammingLanguages

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.2

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Course Objectives

To learn how to solve problems by writing computer programs.

To learn how to design a computer program.

To learn how to program in C++.

To learn how to debug a computer program.To learn object-oriented programming.

To prepare you for COMP151, COMP171, etc.

Question: computer science = programming?

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Whats a Computer Program?

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Whats a Computer Program? ..

Human work model

Computer work model

WORKERwork output

HUMANINSTRUCTIONS

work outputCOMPUTER

PROGRAM

A computer program is a set of machine-readable instructionsthat tells a computer how to perform a specific task.(During the execution of the program, it may interact withthe users and its environment.)

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von Neumann Computer Architecture

ControlUnit

Memory

I/O device

results of operations instructions/data

CPU

ALU

Designed by John von Neumann, a mathematician, in 1945.

It is still todays dominant computer architecture.

For efficiency, many programming languages, including C++,are designed to take advantage of the architecture.

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Is This a Computer?

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Whats a Programming Language for?

Bjarne Stroustrup (C++ designer, 1994):tool for instructing machines?

means for communicating between programmers?

vehicle for expressing high level designs?

notation for algorithms?way of expressing relationships between concepts?

tool for experimentation?

means for controlling computerized devices?

collection of neat features?

His answer: All of the above except

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.8

C

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Can You Understand This?

0000100100101110011001100110100101101100011001010000100100100010011011000110010101100011011101000111010101110010011001010011000100101110011000110010001000001010011001110110001101100011001100100101111101100011011011110110110101110000011010010110110001100101011001000010111000111010000010100010111001110011011001010110001101110100011010010110111101101110000010010010001000101110011101000110010101111000

0111010000100010000010100000100100101110011000010110110001101001011001110110111000100000001101000000101000001001001011100110011101101100011011110110001001100001011011000010000001101101011000010110100101101110000010100000100100101110011101000111100101110000011001010000100100100000011011010110000101101001011011100010110000100011011001100111010101101110011000110111010001101001011011110110111000001010000010010010111001110000011100100110111101100011000010010011000000110100000010100110110101100001011010010110111000111010000010100000100100100001001000110101000001010010010011110100110001001111010001110101010101000101001000110010000000110000000010100000100101110011011000010111011001100101001000000010010101110011011100000010110000101101001100010011001000111000001011000010010101110011011100000000101000001010000010010010000100100011010100000101001001001111010011000100111101000111010101010100010100100011001000000011000100001010000010010110110101101111011101100010000000110001001011000010010101101111001100000000101000001001011100110111010000100000001001010110111100110000001011000101101100100101011001100111000000101101001100100011000001011101000010100000100101101101011011110111011000100000001100100010110000100101011011110011000000001010000010010111001101110100001000000010010101101111001100000010110001011011001001010110011001110000001011010011001000110100010111010000101000001001011011000110010000100000010110110010010101100110011100000010110100110010001100000101110100101100001001010110111100110000000010100000100101101100011001000010000001011011001001010110011001110000001011010011001000110100010111010010110000100101011011110011000100001010000010010110000101100100011001000010000000100101011011110011000000101100001001010110111100110001001011000010010101101111001100000000101000001001011100110111010000100000001001010110111100110000001011000101101100100101011001100111000000101101001100100011

100001011101000010100000100101101101011011110111011000100000001100000010110000100101011010010011000000001010000010010110001000100000001011100100110001001100001100010000101000001001011011100110111101110000000010100010111001001100010011000011000100111010000010100000100101110010011001010111010000001010000010010111001001100101011100110111010001101111011100100110010100001010001011100100110001001100011001100110010100110001001110100000101000001001001011100111001101101001011110100110010100001001001000000110110101100001011010010110111000101100001011100100110001001100011001100110010100110001001011010110110101100001011010010110111000001010000010010010111001101001011001000110010101101110011101000000100100100010010001110100001101000011001110100010000000101000010001110100111001010101001010010010000000110010001011100011100000101110001100010010001000001010

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.9

H Ab Thi ?

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How About This?

main:

!#PROLOGUE# 0save %sp,-128,%sp

!#PROLOGUE# 1

mov 1,%o0

st %o0,[%fp-20] mov 2,%o0

st %o0,[%fp-24]

ld [%fp-20],%o0

ld [%fp-24],%o1

add %o0,%o1,%o0

st %o0,[%fp-28]

mov 0,%i0

nop

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.10

I Thi B N ?

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Is This Better Now?

#include

int main()

{

int x, y, z;

x = 1 ;

y = 2 ;

z = x+y;

return 0;

}

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.11

L l f P i L

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Levels of Programming Languages

machine (binary) language is unintelligible

assembly language is low level

mnemonic names for machine operationsexplicit manipulation of memory addresses/contentsmachine-dependent

high level languagereadable

instructions are easy to rememberfaster coding

less error-prone (fewer bugs?)easier to maintain

no mention of memory locationsmachine-independent = portable

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G l f C P i L

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Genealogy of Common Programming Languages

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C il ti F S t R bl P

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Compilation: From Source to Runnable Program

A compiler translates source

programs into machine codesthat run directly on the targetcomputer.

e.g. a.cpp a.out.

static codes

compile once, run many

optimized codes more efficient

examples: FORTRAN,Pascal, C++

machine A compiler

source code

machine A code

output

run

compile

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Part II

Problem Solving and Computer Programming

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.15

Example: Find the Best Way to Travel from HKUST to

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Example: Find the Best Way to Travel from HKUST to

the Peak Tram Station in Central

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Step 1: Define the Problem

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Step 1: Define the Problem

What do we mean by the best way?

fastest?cheapest?most comfortable?

What types of transportation means are allowed?

How many transits are allowed?

How to obtain the departure location and destination fromthe users?

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Step 2: Develop a Solution

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Step 2: Develop a Solution

Find out all possible bus/minibus/MTRroutes and their fares.

Evaluate all possible combination of their

routes.CS people will ask: how fast can weevaluate all the possible routes?

Select the route that meets our goal

(fastest/cheapest etc.)

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.18

Steps 3 5: Testing Documentation Maintenance

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Steps 3 5: Testing, Documentation, Maintenance

Testing

Test the best route found by your solution.Make sure the conditions have not changed.

has the transport fare been increased?any road construction?

Documentation: Describe and explain the solution.

Maintenance: Test and revise the routes as needed.

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.19

One Solution: efinder ust hk

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One Solution: efinder.ust.hk

Best means: cheapest, fastest, a tradeoff calledefinder-route

how much are you willing to pay to save X minute of traveltime?

Transport vehicles: bus, minibus, MTR.

Allow inputs by typing, mouse selection, voice input.

Get the fare and route information from the companies.

Put all information into a database.

Compute all best routes between any two locations by theFloyd-Warshall algorithm one solution that solves the

well-known all-pairs shortest path problem.(c.f. traveling salesman problem)

Update the database and re-compute all the best routes whenthe route and fare information changes.

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Shortest Path Problem

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Shortest Path Problem

A

B

D

E

1

2

3

4

5

8

6

C

Question: Which is the shortest path from A to E?

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Traveling Salesman Problem

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Traveling Salesman Problem

A

B

D

E

1

2

3

4

5

8

6

C

7

9

Question: A salesman wants to travel all cites {A, B, C, D, E }starting from A, visiting each other city once and only once.Which is the shortest round-trip path?

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Problem Solving

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Problem Solving

Define the problem.Be specific

What are the input(s) and output(s)?Any constraints?Which information is essential?

Can it be done at all?May need refining the problem definition.

Develop a solution.

Outline the solution first.Write down the details step-by-step.

Test the solution.Revise the solution if necessary, based on the test results.

Repeat the develop and test steps until the solution works.

Document the solution.Actually, you should document your solution while you aredeveloping it, not after you have developed it.

Maintain the solution.revise the solution if conditions are changed.

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Programming as Problem Solving

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og a g as ob e So g

Define the problem.

What are the input(s) and output(s)?Any constraints?Which information is essential?

Develop a solution.

Construct an algorithm.

Implement the algorithm by writing a program.Compile the program.

Test the program.

Debug the program.

Document the program as you write the program.Maintain the program

modify the codes when conditions change.enhance the codes to improve the solution.

{ mak, psander, cszz } cse.ust.hk COMP104 (Fall 2007) p.24