MELJUN CORTES Software Development

8/8/2019 MELJUN CORTES Software Development

1/15

SOFTWARE

DEVELOPMENT

Program Planning and Development

Structured Design

Programming Paradigm

Programming Language

Compilers and Interpreters

1 __________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________

PROGRAM PLANNING AND DEVELOPMENT

Five Stages in Program Development

Defining the problem

Designing a solution

Writing the program

Compiling, Debugging, and Testing the programDocumenting the program

2 _________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


1st Stage: Defining the Problem

recognize the need for information

define what outputs are required from the program

2nd Stage: Designing a Solution

breaking the problem into discrete steps known as

“algorithm”

use flowchart to illustrate the sequence of steps

flowchart – a graphical representation of the sequence

of operations a computer is to perform

3 __________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Flowcharting

Terminal

General Input/Output Operation

Process

Comparison

Connector

Predefined Process

Document

Manual Input

4 _________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


2/15


Example: Payroll Flowchart

Start

Read hours

worked and

pay scale

End of

data?

1

YES

Calculate

Employee’s

Pay

Print check

1Print

reportsStop

NO

5 __________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Pseudocode

a version of the instructions describing each step thecomputer must follow

Example: Payroll PseudocodeStart

Read employee's hours worked and hourly wage

Do until end of items

Multiply hours worked by hourly wage to get gross pay

If gross pay is greater than 70K

Then tax rate is 20%

Else tax rate is 15%

Multiply tax rate by gross pay to give tax

Subtract tax and union dues from gross to get netpay

Print check

Read next employee's hours worked and hourly wage

End loop (no more data)

Print reports

6 _________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


3rd Stage: Writing a Program

write the program in a specific programming

language

Types of Programming Statements

comments

declarations

input/output statements

computations

transfer of control

comparison

7 __________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Qualities of a Program

easy to read and understand

efficient

reliable

robust

maintainable

8 _________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


3/15


4th Stage: Compiling, Debugging, and Testing theProgram a compiler is a special program for each programming

language loaded into the computer when that languageis used

Common Compilation Errors

spelling errors syntax errors

improperly sequenced statements

improperly labeled statements

conflict in variable names

illegal names or statements

missing punctuations

9 __________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


logical errors are detected by the programmer in a

debugging process

to be sure that the program will give the correct

output, the program has to be tested by running the

program and inputting data with known outputs

10 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


5th Stage: Documentation of the Program consists of written descriptions and explanations of

programs and other materials associated with anorganization’s data processing system

serves as a guide to programmers and analysts whomust modify or update existing programs and systemprocedures

Other Descriptions a complete description of the contents and formats of all data

inputs, outputs and files to be used

a statement of the hardware requirements for running theprogram as well as estimated processing time and storagerequirements

a statement of software requirements such as utility programsand library programs

11 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

STRUCTURED DESIGN

each major step in the program must bedeveloped as independent module andrepresented in the flowchart as a separate block

program codes will be easier to understand andmore maintainable if you break the logic intosteps, and encompass each step in its ownsubroutine or function

Benefits early detection design flaws

programs can be easily modified

clear and complete documentation

modular design to improve testing

12 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


4/15

STRUCTURED DESIGN

Top-down vs Bottom-up

Top-down

done by recognizing the major components of the

solution, expressing the solution as a sequence of these

major components, and then expanding the major

components similarlyBottom-up

starts by identifying small functions and subroutines

present in the design and moving up towards more

complex procedures

13 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________

STRUCTURED DESIGN

Using Flowcharts

generally involves a top-down analysis of the

problem

based on the assumption that there are four basic

logic patterns

Simple sequence

Selection pattern

Loop pattern

Branch pattern

14 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________

STRUCTURED DESIGN

Simple Sequence Selection Pattern

15 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

STRUCTURED DESIGN

Loop Pattern Branch Pattern

16 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


5/15

STRUCTURED DESIGN

Do-While Structure Case Structure

17 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________

PROGRAMMING PARADIGM

Paradigm

an example, model, or pattern

an idealized pattern of usage under which some

agent can operate

Programming Paradigm a way of thinking about problems and their

solutions, or an approach on how to use a

computer to implement those solutions

18 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Major Programming Paradigms

Imperative

Logical

Functional

Object-Oriented

19 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Imperative Paradigm

characterized by programming with states and

commands that modify the states

implies procedures (or programs) or directions for

performing an action

an abstraction of real computers, which are based

on the Von Neumann machine

assumes that a computer can maintain, through

environment variables, any change in the

computation process

20 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


6/15


Advantage can be easily translated to an efficient machine code, so they are

considered highly efficient

Disadvantage some problems are hard to model using this paradigm

Example: Imperative program that will compute the factorial

of a given number

Function factorial(n)

{ var x = 1;

while(n>0) {

x = x*n;

n = n-1; }

return x;

}

21 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Logical Paradigm

takes a declarative approach to problem-solving

can be divided into three (3) steps

1. a series of definitions/declarations that define the problemdomain

2. statements of relevant facts

3. statements of goals in the form of queries

Advantages

the system solves the problem so programming steps are keptto a minimum

since it is largely based on mathematical logic, proving thevalidity of a given program becomes simple

22 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Example: An illustration of a logical paradigm

23 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Functional Paradigm

based on functional expressions and the evaluation of

these expression

views all programs as functions in a mathematicalsense

Advantages

provide a high level of abstraction; the programming becomesmodular and removes the possibility of creating several errors

not heavily dependent on the assignment operation, so theprograms can be evaluated with many different orders

much more amenable to mathematical proof and analysisthan imperative ones

24 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


7/15


Disadvantages

hard to implement efficiently, because it is hard to

determine if data storage can be re-usable

difficult to solve problems involving many variables or a

lot of sequential activity

25 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Example: Factorial function

Factorial n =

If n = 1 then 1

Else

n * Factorial(n-1);

26 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Example: Function for computing the average of twonumbers

Function for computing the average of two numbers:

(defun avg(X Y) (/ (+ X Y) 2.0))

Function is called by:

> (avg 10.0 20.0)

Function returns:

15.0

27 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Object-Oriented Paradigm

a paradigm in which real world objects are viewed

as separate entities having their own state and

exhibiting their own behavior

focuses on the objects that the programmer is

representing

28 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


8/15


illustrates objects and how they are encapsulated

into modules

Object interface

DATAMethods

29 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


can be divided into four steps

1. identify the problem

2. identify the objects needed for the solution

3. identify messages to be sent to the objects

4. create a sequence of messages to the objects that

solve the problem

30 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Example:

1. Problem identification: Computer the sum of two

numbers and printout the result

2. Object identification:

Num1 – first number (object)

Num2 – second number (object)

Sum – result of the addition of the two numbers

3. Message identification:

+ aNum – sent to the receiver object with parameter aNum

print – displays the value of the receiver object

4. Object-message sequences: (Num1 + Num2)print

31 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Other Programming Paradigms

Tree

viewing code or data in a highly hierarchical manner

Expert System

organizes data by using a list or pool of rules that aresometimes recycled through constantly

Stream

based on the idea that input and output of smallerprograms or utilities can be linked together

Neural Network

based on the concepts that computers are programmedin the same way as how humans think

32 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


9/15

PROGRAMMING LANGUAGE

Language

defined as a system for communication

written language use symbols (characters) to buildwords

Vocabulary

refers to entire set of words Syntax and Grammar

define the way in which the words can be meaningful

when combined

Semantics

actual meaning of words and combinations of words

33 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Machine Language

the lowest level of programming language

only language understood by computers and

consists of pure numbers; takes the form of “1” or

“0”

each machine instruction has two (2) parts:

op code (operation code)

operand

34 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Low-Level Language

also called as assembly language

easier to understand than machine language

35 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


programmers must be highly skilled in two areas:

must know a great deal about the internal workings of

the microprocessor, and a broad technical knowledge of

the computer is needed

must be very detail oriented; every step of the computer

must be coded, and the actual numerical address of the

instructions and data must be specified

36 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


10/15


Example: Using assembly language to multiply 87

and 243 and saving the result in the memory

37 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


High-Level Language

enables a programmer to write programs that aremore or less independent of a particular type ofcomputer

closer to human language than the machine

language easier to understand and allows the programmer to

focus on solving the problem rather than knowinghow to program the computer

Examples: Ada, Algol, BASIC, COBOL, C, C++,FORTRAN, LISP, Pascal, Prolog

38 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


BASIC

Beginner’s All-purpose Instruction Code

developed by John Kemeny and Thomas Kurtz in the

early 1960’s

intended as an easy to learn interactive language for the

students

Advantages

simplicity and flexibility

allows basic manipulation of text

provides built-in functions such as logarithms, square root,

trigonometric functions, and random number generator

39 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Example: Using BASIC program to multiply 87 and 243

and printing the result

40 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


11/15


FORTRAN

Formula Translator

the oldest high-level programming language

developed in the mid 1950’s by John Backus

primarily intended as a high-level language used for

programming scientific, mathematical, and engineeringapplications

41 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Advantages

procedure-oriented language with excellent mathematical

capabilities

its pattern is similar to the BASIC language; a programmer who

is familiar with FORTRAN can easily write programs in BASIC

Disadvantages closely resembles mathematical notations, it is very difficult for

non-programmer to understand or find the errors in a program

not suited as a business application language for it does not

have the capability to develop programs that involve file

maintenance, editing of data, or document production

42 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


Example: Using FORTRAN program to multiply 87 and

243 and printing the result

43 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


COBOL

Common Business-Oriented Language

the most frequently used business programming

language

used extensively in business, education, and government

started in the early 1960’s when a committee led by US

Department of Defense and other computer users and

manufacturers known as CODASYL (Conference of Data

Systems Languages) wanted to develop a common

business programming language

Dr. Gray Murray Hopper was a major contributor to the

structure and development of the language

44 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


12/15


Advantages

easy to understand even for non-programmers

self-explanatory and well-documenting

good literary capability which means that it is good in

manipulating words, sentences, or paragraphs of text material

strong file-handling capabilities

machine independent

Disadvantages

programs tend to be wordy and quite long

limited computational capabilities which makes it inappropriate

for applications that require computations

45 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Example: Using COBOL program to multiply 87 and 243


46 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


PASCAL

the language named after the seventeenth century

French mathematician Blaise Pascal who constructed

one of the first adding machines

a high-level language developed by Niklaus Wirth of

Zurich, Switzerland in the late 1960’s

one of the first languages developed using a structured

programming approach

47 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Characteristics

Pascal programs consist of modules, and each module

performs a specific function

the statements in the module can be organized into levels,

and the level of the statement is shown by its degree ofindention from the margin to follow the program logic easily

statements in a Pascal program are composed of reservedwords, symbols, and identifiers

reserved words are words that have a special meaning to thePascal compiler

symbols used in Pascal include mathematical symbols andpunctuation marks

identifiers are names that represent various constants,variables, procedures, or functions

48 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


13/15


Advantages

relatively easy to learn

powerful and efficient language

strong graphics capabilities

Disadvantages

not as standard as COBOL or BASIC

poor input and output capabilities

limited file-handling capabilities

does not possess the ability to manipulate large collection of

numbers or words

49 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Example: Using PASCAL program to multiply 87 and 243


50 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


C Language

a high-level programming language developed by Dennis

Ritchie at the Bell Laboratories in 1972

named C, because it was influenced by another language

called B developed by Ken Thompson

originally designed as a systems programming language

used to write operating systems programs

51 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________


Advantages

allows direct manipulation of bits, bytes and words that are

similar to assembly language

useful for numerical, text processing, and database programs

very good graphics programming capabilities

Disadvantages

not intended as a language for non-programmers, unlike BASIC

and COBOL; if you are not familiar with the language, you will not

understand the structure

52 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


14/15


Example: Using C program to multiply 87 and 243 and

printing the result

53 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


C++ Language

developed by Bjarne Stroustrup while working at the Bell

Laboratories

considered a superset of C, and has the same

capabilities as C with added object-oriented features

Example: Using C++ program to multiply 87 and 243 andprinting the result

54 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________


JAVA Language

popular programming language for creating applications

on the Web

“Oak”, was developed in December 1990 by Sun

Microsystems

Reasons to Use Java

Simple and familiar

Object-oriented

Architecture-neutral

Portable

Distributed

Secure

55 _________________________

____________________________

____________________________

____________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

COMPILERS AND INTERPRETERS

56 ________________________

___________________________

___________________________

___________________________

___________________________

___________________________

___________________________ ___________________________

___________________________


15/15


Compiler

a program that translates a program written in a high-level language and translates it into machine language

Advantages

compiled machine codes run much faster than interpretedones

compiled codes occupy less memory during execution

once a program is compiled it can be re -run anytime

Disadvantages

the program can only be executed once the translation iscomplete

any change to the source code requires a completerecompilation

57 _________________________

____________________________

____________________________

____________________________ ____________________________

____________________________

____________________________

____________________________

____________________________


Interpreter

translates and executes the program line by line

translates high-level instructions into an intermediateform, which it then executes

Advantages

faster and easier to detect errors in the interpreted programthan the compiled program

easier and faster to make changes to the program whichreduces development time especially for large programs

Disadvantages

uses more memory and much slower than compiled codes

no copy of the translated code exist; if you want to re-run theprogram it must be interpreted all over again

58 ________________________

___________________________

___________________________

___________________________ ___________________________

___________________________

___________________________

___________________________

___________________________

MELJUN CORTES Software Development

Documents

Transcript of MELJUN CORTES Software Development