1. SOFTWARE DESIGN & DEVELOPMENT
Programming Foundations

2. Lecture Topics The Evolution of Hardware & Software
Computer Components
Computer Programming
Programming Life-Cycle Phases
Creating an Algorithm
Machine Language vs. High Level Languages
Compilation and Execution Processes
Generic instruction functionality & control structures
Two different approaches to building program modules
Case study

3. Evolution of Hardware Generation Time Period Principal Events
1642 – 1945
Mechanical calculators 1
1945 – 1955
Vacuum tubes 2
1955 – 1965
Transistors 3
1965 – 1971
Integrated circuits 4
1971 – Present
Computer chips

4. Evolution of Hardware (Pre 1900)
Abacus  first known calculating machine; used for more than 4,000 years
1623  first mechanical calculator (Schickard)
1642  first automatic mechanical calculator (Pascal)
1804  punched block (Jacquard); forerunner of what we now call programming
1822 & 1833  Babbage invented difference engine and then an analytical engine ( a general purpose calculating device)
1854  Boole created an algebra based on logic
1886  Hollerith created punched cards which reduced the time needed to tabulate US census by more than 50%

5. Evolution of Hardware (Post 1900)
1945  Von Neumann created a computer which was the first to use the idea of a stored program
1949  Cambridge Uni: first large scale computer using stored-program concept
1951  first commercial computer, the UNIVAC
1954  first transistorized computer by Bell Labs
1960’s  advent of minicomputers using integrated circuits
1971  Intel 4004 chip starts evolution of placing power of large scale computer in a very small area
1970’s first PC’s & supercomputers
1980’s  networks of computers of varying computing power

6. Computer Architectures
Traditional design of a general purpose computer is called a Von Neumann computer – instructions and data co-exist in RAM
Such a machine fetches an instruction from memory, decodes the instruction, and then executes it
One way to use such a computer is by pipelining (see following)
Not all computers are of this type. Other types include:
A parallel processing computer (share memory & control unit)
An array processor (each processor has own memory but share the same control unit)
Variations on the former two parallel processing options
Reduced instruction set computers

7. An example of pipelining
Time
Time+1
Time+2
Time+3
Time+4
Time+5
Time+6
Time+7
Inst. # 1
Fetch
Decode
Execute
Inst. # 2
Inst. # 3
Inst. # 4
Inst. # 5
Inst. # 6 ….

8. Software Evolution Generation Time period Principal Events 1
1945 – present
Machine languages (binary form) 2
1953 – present
Assembly languages (symbolic mnemonic code) 3
present
High level languages (Fortran, COBOL, Basic, C) 4
1971 (OOP’s) 1980’s (4GL’s) – present
4GL’s using databases, OOP languages (Smalltalk, C++) 5
present
Logic programming (Prolog)

9. Memory Unit ( RAM & Registers )
Computer Components
Peripherals
Central Processing Unit ( CPU )
Input Device
Control Unit
Arithmetic Logic Unit
Output Device
Auxiliary
Storage
Device
Memory Unit ( RAM & Registers )

10. 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.

11. Central Processing Unit
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.

12. 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.

13. What is Programming?
Planning or scheduling the performance of a task or event.
Computer: a programmable device that can store, retrieve, and process data
STEP 1
STEP 2
STEP 3

14. What is Computer Programming?
It is the process of planning a sequence of steps (called instructions) for a computer to follow.
Computer program: A sequence of instructions to be performed by a computer
We, as humans, must specify what we want done and the order in which we want it done.
STEP 1
STEP 2
STEP 3

15. Programming Life Cycle Phases
Problem-Solving
Implementation
Maintenance

16. 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

17. Sample Problem
A programmer needs an algorithm to determine an employee’s weekly wages.
How would the calculations be done by hand?

18. One Employee’s Wages
In one week an employee works 52 hours at the hourly pay rate of $ 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 $ = $
12 x 1.5 x $ = $
___________ $

19. Weekly Wages, in General
If hours are more than 40.0, then
wages = (40.0 * payRate) + (hours ) * 1.5 *payRate
otherwise,
wages = hours * payRate
RECALL EXAMPLE
( 40 x $ ) + ( 12 x 1.5 x $ ) = $

20. An Algorithm is . . .
a step-by-step procedure for solving a problem in a finite amount of time.

21. 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

22. What is a Programming Language?
It is a language with strict grammar rules, symbols, and special words used to construct a computer program.

23. 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

24. Implementation Phase: 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

25. 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

26. Programming Life Cycle
Problem-Solving Phase
Analysis and Specification
General Solution ( Algorithm )
Verify
Implementation Phase
Concrete Solution ( Program )
Test
Maintenance Phase
Use
Maintain

27. A Tempting Shortcut? DEBUG REVISE REVISE DEBUG DEBUG REVISE Shortcut?
CODE
GOAL
TEST
THINKING
CODE

28. 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 = bytes
1 MB = x = 1,048,576 bytes

29. How Many Possible Digits?
binary (base 2) numbers use 2 digits: JUST 0 and 1
decimal (base 10) numbers use 10 digits: 0 THROUGH 9

30. 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 language that can be directly used by the computer

31. 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

32. Three C++ Program Stages
myprog.cpp
myprog.obj
myprog.exe
SOURCE
OBJECT
EXECUTABLE
written in
machine
language
C++
via compiler
via linker
other code
from libraries,
etc.

33. 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

34. The computer program translation process?
Computers are stupid, they understand only ones and noughts, or more properly high and low voltages on their internal sets of wires.
Thus
might be a program to a computer.
This is called machine code.

35. Assemblers and Mnemonics
Machine code is a bit difficult to read and to program in
It is also easy to make mistakes in machine code.
What about a language that uses a code instead of a machine instruction, in fact a
mnemonic
A program called an assembler can turn these mnemonics into machine code relatively easily;
this is because the relationship between an assembly language instruction and a machine instruction is close to 1:1.

36. Assembly language programs
Consider this assembly language program
LD A,06H
LD C,A
LD A,07H
LD E,A
SLL C,02H
LD A,E
LD 96H,A
DEC DE
LD A,D
OUT A,044H
LD 97HA
Assembly languages are low level programming languages because they are “close” to the processor.
Each processor will have its own assembly language
Mnemonics
English

37. High Level programming languages
Fortran Formulae Translator
COBOL Common Business Oriented Language
These programs were more orientated to the human rather than the machine.
COBOL:
MOVE ER-EMPLOYEE-LINE-OUT TO
ER-EMPLOYEE-HIRE-YEAR-OUT
READ NAME-ADDRESS-FILE-IN
AT END MOVE "YES" TO WS-END-OF-FILE-SWITCH.
A high level program requires a program to convert it into executable code: a Compiler.

38. Compilers and compiling?
Compilers must examine and interpret the computer program.
It must then produce code that can execute or run on the computer processor.
This usually takes place in a number of stages, which are for the most part hidden from the programmer.
First of all the programmer must place his/her program in a text file.
These consist of data definitions and instructions to the computer.
The compiler must firstly check that you have obeyed the grammatical rules of the language.

39. The compilation process from the programmers view
Edit
Compilation
Source code
(.cpp file)
Object code
(.obj file)
Error listing on the standard output. In your case to the screen.
Errors detected

40. Compiler processes
The code is then compiled proper and then an assembly process is performed
Some compilers allow you to have a look at the assembly language generated from your program
It will be A LOT!
Some languages just go straight to the linking stage from the compilation stage.
Linking locates and incorporates into your final executable file those bits of code that have been pre-written for you.
Most often the I/O code has been pre-written.

41. Compiler processes Pre-compiled programs such as I/O (.obj files)
Linking
Edit
Source code
(.cpp file)
Compilation
Object code
(.obj file)
Executable code
(.exe file)
Error listing on the standard output. In your case to the screen.
Errors detected

42. Computer Program Instructions
“The instructions in a programming language reflect the operations a computer can perform:
A computer can transfer data from one place to another
A computer can input data from an input device …. and output data to an output device….
A computer can store data into and retrieve data from its memory and secondary storage…
A computer can compare two data values for equality and inequality
A computer can perform arithmetic operations … very quickly” (page 14, from the text)
To implement these operations requires the use of certain control structures…..

43. 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

44. SEQUENCE
Statement
Statement
Statement
. . .

45. SELECTION (branch) IF Condition THEN Statement1 ELSE Statement2 True
. . .
Statement2
False

46. LOOP (repetition) WHILE Condition DO Statement1 False . . . Condition
True
Statement

47. SUBPROGRAM (function)
. . .
SUBPROGRAM1
SUBPROGRAM1
a meaningful collection
of SEQUENCE,
SELECTION, LOOP,
SUBPROGRAM

48. Two Approaches to Building Manageable Modules
FUNCTIONAL DECOMPOSITION
OBJECT-ORIENTED DESIGN
Divides the problem
into more easily handled
subtasks, until the
functional modules
(subproblems) can
be coded.
Identifies various
objects composed of
data and operations,
that can be used
together to solve
the problem.
FOCUS ON: processes FOCUS ON: data objects

49. Functional Design Modules
Find
Weighted
Average
Print
Main
Get Data
Prepare
File for
Reading
Print Data
Print Heading

50. Object-Oriented Design
A technique for developing a program in which the solution is expressed in terms of objects -- self- contained entities composed of data and operations on that data.
cin
cout
>>
<<
get
Private data
setf
Private data . .
ignore

51. Procedural vs. Object-Oriented Code
“Read the specification of the software you want to build. Underline the verbs if you are after procedural code, the nouns if you aim for an object-oriented program.”
Brady Gooch, “What is and Isn’t Object Oriented Design,”

52. 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.

53. One Employee’s Wages
In one week employee ID # 4587 works hours at the hourly pay rate of $ 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 $ = $
12 x 1.5 x $ = $
___________ $

54. 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

55. 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

56. Week’s Wages, in General
If hours are more than 40.0, then
wages = (40.0 * payRate) + (hours ) * 1.5 *payRate
otherwise,
wages = hours * payRate
RECALL EXAMPLE
( 40 x $ ) + ( 12 x 1.5 x $ ) = $

57. 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

58. C++ Program // ***************************************************
// 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

59. 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

60. 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 }

61. 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;