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Author,Nell Dale
Chip Weems
Mark Headington
Published By
Higher Education Press
Jones and Bartlett Publishers
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Instructor,Yu RuiGuo
E-mail:rgyu@tju.edu.cn
Assistant,Li QingSen
E-mail:qingsenli@eyou.com
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Overview of Programming
and Problem Solving
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Chapter 1 Topics
Computer Programming
Programming Life-Cycle Phases
Creating an Algorithm
Machine Language vs,High Level
Languages
Compilation and Execution Processes
C++ History
Computer Components
Computing Profession Ethics
Problem-Solving Techniques
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What is Computer Programming?
It is the process of planning a
sequence of steps (called
instructions) for a computer to
follow.
STEP 1
STEP 2
STEP 3
.,,
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Programming Life Cycle Phases
1 Problem-Solving
2 Implementation
3 Maintenance
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Analysis
and
specification
General Solution
(algorithm)
Verify
Concrete solution
(program)
Test
Maintenance phase
Figure 1-1 Programming Process
PROBLEM-SOLVING PHASE IMPLEMENTATION PHASE
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Problem-Solving Phase
ANALYZE the problem and SPECIFY
what the solution must do
develop a GENERAL SOLUTION
(ALGORITHM) to solve the problem
VERIFY that your solution really
solves the problem
The First Step
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Sample Problem
A programmer needs an algorithm to
determine an employee’s weekly
wages,How would the calculations
be done by hand?
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One Employee’s Wages
In one week an employee works 52
hours at the hourly pay rate of $24.75,
Assume a 40.0 hour normal work week
and an overtime pay rate factor of 1.5
What are the employee’s wages?
40 x $ 24.75 = $ 990.00
12 x 1.5 x $ 24.75 = $ 445.50___________
$ 1435.50
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If hours are more than 40.0,then
wages = (40.0 * payRate) + (hours - 40.0) * 1.5
*payRate
otherwise,
wages = hours * payRate
Weekly Wages,in General
RECALL EXAMPLE
( 40 x $ 24.75 ) + ( 12 x 1.5 x $ 24.75 ) = $1435.50
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An Algorithm is,,,
a step-by-step procedure for solving
a problem in a finite amount of time.
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Algorithm to Determine an
Employee’s Weekly Wages
1,Get the employee’s hourly payRate
2,Get the hours worked this week
3,Calculate this week’s regular wages
4,Calculate this week’s overtime wages (if any)
5,Add the regular wages to overtime wages (if
any) to determine total wages for the week
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What is a
Programming Language?
It is a language with strict grammar
rules,symbols,and special words
used to construct a computer
program,
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Implementation Phase:
Program
translating your algorithm into a
programming language is called CODING
with C++,you use
Documentation -- your written comments
Compiler -- translates your program
into machine language
Main Program -- may call subalgorithms
The Second Step
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Implementation Phase(cont.):
Test
TESTING your program means running
(executing) your program on the
computer,to see if it produces correct
results
if it does not,then you must find out
what is wrong with your program or
algorithm and fix it--this is called
debugging
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Maintenance Phase
USE and MODIFY the program to
meet changing requirements or
correct errors that show up in using
it
maintenance begins when your
program is put into use and
accounts for the majority of effort on
most programs
The Third Step
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Programming Life Cycle
1 Problem-Solving Phase
Analysis and Specification
General Solution ( Algorithm )
Verify
2 Implementation Phase
Concrete Solution ( Program )
Test
3 Maintenance Phase
Use
Maintain
Summary
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A Tempting Shortcut?
GOAL
THINKING CODE
REVISE REVISE
REVISE
DEBUG
DEBUG
DEBUG
TEST
CODE
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Memory Organization
two circuit states correspond to 0 and 1
bit (short for binary digit) refers to a single
0 or 1,Bit patterns represent both the
computer instructions and computer data
1 byte = 8 bits
1 KB = 1024 bytes
1 MB = 1024 x 1024 = 1,048,576 bytes
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How Many Possible Digits?
binary (base 2) numbers use 2 digits,
JUST 0 and 1
Octal (base 8) numbers use 8 digits:
0 THROUGH 7
decimal (base 10) numbers use 10 digits,
0 THROUGH 9
Hexadecimal (base 16) numbers 16 digits:
0 THROUGH 15
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Machine Language
is not portable
runs only on specific type of computer
is made up of binary-coded instructions
(strings of 0s and 1s)
is the only programming language that can be
directly used by the computer
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High Level Languages
are portable
user writes program in language similar to
natural language
examples -- FORTRAN,COBOL,
Pascal,Ada,Modula-2,C++,Java
most are standardized by ISO/ANSI to
provide an official description of the
language
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Three C++ Program Stages
other code
from libraries,
etc.
written in
machine
language
written in
machine
language
written in
C++
via compiler via linker
SOURCE OBJECT EXECUTABLE
myprog.cpp myprog.obj myprog.exe
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Java Programming Language
achieves portability by using both a
compiler and an interpreter
first,a Java compiler translates a Java
program into an intermediate bytecode--not
machine language
then,an interpreter program called the Java
Virtual Machine (JVM) translates a single
instruction in the bytecode program to
machine language and immediately runs it,
one at a time
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Four Basic Control Structures
a sequence is a series of statements that
execute one after another
selection (branch) is used to execute
different statements depending on certain
conditions
Looping (repetition) is used to repeat
statements while certain conditions are
met.
a subprogram is used to break the
program into smaller units
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SEQUENCE
Statement Statement Statement,,,
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SELECTION (branch)
IF Condition THEN Statement1 ELSE Statement2
Statement1
Statement
Statement2
Condition,,,
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LOOP (repetition)
Statement
Condition,,,
False
WHILE Condition DO Statement1
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SUBPROGRAM (function)
SUBPROGRAM1,,,
SUBPROGRAM1
a meaningful collection
of SEQUENCE,
SELECTION,LOOP,
SUBPROGRAM
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Computer Components
Arithmetic Logic Unit
Control Unit
Auxiliary
Storage
Device
Memory Unit ( RAM & Registers )
Central Processing Unit ( CPU )
Input Device
Output Device
Peripherals
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Memory Unit
is an ordered sequence of storage cells,
each capable of holding a piece of
information
each cell has its own unique address
the information held can be input data,
computed values,or your program
instructions.
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Central Processing Unit (CPU)
has 2 components to execute program
instructions
Arithmetic/Logic Unit performs
arithmetic operations,and makes
logical comparisons.
Control Unit controls the order in which
your program instructions are executed.
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Peripherals
are input,output,or auxiliary storage devices
attached to a computer
Input Devices include keyboard and mouse.
Output Devices include printers,video
display,LCD screens.
Auxiliary Storage Devices include disk
drives,scanners,CD-ROM and DVD-ROM
drives,modems,sound cards,speakers,
and digital cameras.
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Some C++ History
1972,Dennis Ritchie at Bell Labs
designs C and 90% of UNIX is then
written in C
Late 70’s,OOP becomes popular
Bjarne Stroustrup at Bell Labs adds
features to C to form,C with Classes”
1983,Name C++ first used
1998,ISO/ANSI standardization of C++
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Computing Profession Ethics
copy software only with permission from
the copyright holder
give credit to another programmer by
name whenever using his/her code
use computer resources only with
permission
guard the privacy of confidential data
use software engineering principles to
develop software free from errors
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What is Computer Science?
The Computing Curriculum 1991 (ACM/IEEE)
Algorithms and Data Structures
Architecture
Artificial Intelligence and Robotics
Database and Information Retrieval
Human-Computer Communication
Numerical and Symbolic Computation
Operating Systems
Programming Languages
Software Engineering
Social and Professional Context
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Problem Solving Techniques
ASK QUESTIONS -- about the data,the
process,the output,error conditions.
LOOK FOR FAMILIAR THINGS -- certain
situations arise again and again.
SOLVE BY ANALOGY -- it may give you a
place to start.
USE MEANS-ENDS ANALYSIS --
Determine the I/O and then work out the
details.
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More Problem Solving Techniques
DIVIDE AND CONQUER -- break up large
problems into manageable units.
BUILDING-BLOCK APPROACH -- can you
solve small pieces of the problem?
MERGE SOLUTIONS -- instead of joining
them end to end to avoid duplicate steps.
OVERCOME MENTAL BLOCK -- by
rewriting the problem in your own words.
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Company Payroll Case Study
A small company needs an interactive
program to figure its weekly payroll,
The payroll clerk will input data for
each employee,and each employee’s
wages and data should be saved in a
secondary file,
Display the total wages for the week on
the screen.
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One Employee’s Wages
In one week employee ID # 4587 works
52 hours at the hourly pay rate of 24.75,
Assume a 40.0 hour normal work week
and an overtime pay rate factor of 1.5.
What are the employee’s wages?
40 x $ 24.75 = $ 990.00
12 x 1.5 x $ 24.75 = $ 445.50___________
$ 1435.50
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Problem-Solving Phase
What information will be used?
INPUT DATA from outside the program
FORMULA CONSTANTS used in program
COMPUTED VALUE produced by program
OUTPUT RESULTS written to file or screen by
program
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Problem-Solving Phase
INPUT DATA FORMULA
CONSTANTS
OUTPUT
RESULTS
Employee ID
Number
Hourly payRate
Hours worked
Normal work
hours ( 40.0 )
Overtime pay
rate factor (1.5)
Hourly payRate
Hours worked
Wages
COMPUTED VALUE
Wages
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If hours are more than 40.0,then
wages = (40.0 * payRate) + (hours - 40.0) * 1.5
*payRate
otherwise,
wages = hours * payRate
Week’s Wages,in General
RECALL EXAMPLE
( 40 x $ 24.75 ) + ( 12 x 1.5 x $ 24.75 ) = $1435.50
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Algorithm for Company Payroll
Program
initialize total company payroll to 0.0
repeat this process for each employee:
1,Get the employee’s ID empNum
2,Get the employee’s hourly payRate
3,Get the hours worked this week
4,Calculate this week’s wages
5,Add wages to total company payroll
6,Write empNum,payRate,hours,wages to
file
write total company payroll on screen
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// ***************************************************
// Payroll program
// This program computes each employee’s wages and
// the total company payroll
// ***************************************************
#include <iostream> // for keyboard/screen I/O
#include <fstream> // for file I/O
using namespace std;
void CalcPay ( float,float,float& ) ;
const float MAX_HOURS = 40.0; // Maximum normal hours
const float OVERTIME = 1.5; // Overtime pay factor
C++ Program
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C++ Code Continued
int main( )
{
float payRate; // Employee’s pay rate
float hours; // Hours worked
float wages; // Wages earned
float total; // Total company payroll
int empNum; // Employee ID number
ofstream payFile; // Company payroll file
payFile.open(,payfile.dat” ); // Open file
total = 0.0; // Initialize total
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cout <<,Enter employee number:,; // Prompt
cin >> empNum; // Read ID number
while ( empNum != 0 ) // While not done
{
cout <<,Enter pay rate:,;
cin >> payRate ; // Read pay rate
cout <<,Enter hours worked:,;
cin >> hours ; // and hours
worked
CalcPay(payRate,hours,wages); // Compute wages
total = total + wages; // Add to total
payFile << empNum << payRate
<< hours << wages << endl;
cout <<,Enter employee number:,;
cin >> empNum; // Read ID number
}
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cout <<,Total payroll is,
<< total << endl;
return 0 ; // Successful completion
}
// ***************************************************
void CalcPay ( /* in */ float payRate,
/* in */ float hours,
/* out */ float& wages )
// CalcPay computes wages from the employee’s pay rate
// and the hours worked,taking overtime into account
{
if ( hours > MAX_HOURS )
wages = (MAX_HOURS * payRate ) +
(hours - MAX_HOURS) * payRate * OVER_TIME;
else
wages = hours * payRate;
}