1) Introduction to Computer Programming

8/3/2019 1) Introduction to Computer Programming

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Introduction to Computer Introduction to Computer ProgrammingProgramming



Review on Computer TerminologiesReview on Computer Terminologies

Computer something that ³computes´

takes input

processes input (according to particular steps )

produces output

Program a sequence of instruction executed

Computer P

rogram A set of detailed, step-by-step instruction that

directs the computer what to do also called assoftware



Terminologies Cont..Terminologies Cont..

A computer program may also be called:

Project

Application

Solution



Review on Computer TerminologiesReview on Computer Terminologies

Programming Language

A set of rules that provides a way of telling the computer

what operations to perform

is a set of syntactic and semantic rules used to define

computer programs. Computer Programmer

Creates computer program

Requirement: analysis, logic, knowledge w/ programming

language to use



Program Development CycleProgram Development Cycle

Software refers to a collection of instructions for the

computer

The computer only knows how to do what the

programmer tells it to do

Therefore, the programmer has to know how to

solve problems



Performing a Task on the Computer Performing a Task on the Computer

Determine Output

Identify Input

Determine process necessary to turn given Input

into desired Output



Steps in Program DevelopmentSteps in Program Development

1. Identification and analysis of the problem

2. Planning the solution

3. Setting up an algorithm program

4. Coding the program5. Program Compilation

6. Running , testing and debugging

7. Documentation



Programming ProcessProgramming Process

Create/Edit

Program

Compile

Program

Execute

Program

Compile Errors? Run-Time Errors?

Source

Program

Object

Program



Identification and analysis of the problemIdentification and analysis of the problem

Determine the ff:

Input -> Data

Output -> Information

Purpose: to analyze thoroughly

to understand the problem

to identify the inputs and outputs



Review program specs

Meet with analysts / users

Identify program components

(IPO ± Input, Processing, Output))

1. Defining the Problem1. Defining the Problem



2. Planning the Solution (Design)2. Planning the Solution (Design)

Design the algorithm

An algorithm is a finite series of logical steps

required to solve a particular problem.

Items covered in a next few slides

Use flowcharts and pseudocode.

Use the appropriate programming flow control

structures in the design

Desk check the solution



Example: Identification and analysis of theExample: Identification and analysis of theproblemproblem

Problem 1:

Write a program to will compute and display the

sum of five (5) number

Inputs:

7,8,3,2,1

Process

7+8+3+2+1

Output SUM



SUMSUM = 7 + 8 + 3 + 2 + 17,8,3,2,1

OutputProcessingInput

Example: IPO TableExample: IPO Table



Setting up an algorithm programSetting up an algorithm program

Design an Algorithms

A detailed, step by step solution to a program

the a straight forward sequence of logical / mathematical

instructions that must terminate (return 0) and describes

data to be processed to produce a desired options. Tools

Flowcharting

Pseudocode

³ false´ code

involves actually writing a program, written in English

rather than in a computer language.

See slides of analysis of algo



Algorithms in The Real World Algorithms in The Real World

We use algorithms almost daily in our lives

without realizing it

For example

an instruction manual

a cooking recipe

a knitting pattern



FlowchartingFlowcharting

A flowchart is a pictorial representation of an

algorithm or logical steps.

Each step is represented by a symbol and the

arrows indicate the flow and order of the steps.

The shape of the symbol indicates the type of

operation that is to occur.

Flowcharts may help the more visual students learn

and understand logic.



Flowchart SymbolsFlowchart Symbols

Begin or End Input or Output

ProcessingDecision

Branch or Direction of Flow



Flow Control StructuresFlow Control Structures

Flow control is the order in which statements are

executed.

There are four control structures.

1. Sequence Control2. Selection Control

Also referred to as branching (if and if-else)

3. Case Control (similar to selection)

4. Repetition Control (loops)



FlowchartFlowchart ± ± Sequence ControlSequence Control

Begin

Input

price, qty

subtotal =

price * qty;

Output

subtotal

End



FlowchartFlowchart ± ± Selection ControlSelection ControlCalculate Handling based on total weight of the order Calculate Handling based on total weight of the order

If weight < 10

Handling = 3.00

Handling = 1.00

Output Handling

True

False

InputWeight



FlowchartFlowchart ± ± Case ControlCase Control



FlowchartFlowchart ± ± Repetition Control (loops)Repetition Control (loops)



Example: FlowchartingExample: Flowcharting

START

SUM = 7 + 8 + 3 +2 +1

END



Example: PsuedocodeExample: Psuedocode

Begin procedure

Input 7,8,3,2,1

Sum = 7+8+3+2+1

Output SUM

End procedure



Coding the programCoding the program

Translating algorithms into a formal programming

language

IDE / Programming Environment

Integrated Development Environment

A comprehensive package that includes text editors,

translation and debugging software



Setting up an algorithm programSetting up an algorithm program

Design an Algorithms

A detailed, step by step solution to a program

the a straight forward sequence of logical / mathematical

instructions that must terminate (return 0) and describes

data to be processed to produce a desired options. Tools

Flowcharting

Psuedocode

³ false´ code

involves actually writing a program, written in English

rather than in a computer language.



SUMSUM = 7 + 8 +

3 + 2 + 1

7,8,3

,2,1

OutputProcessingInput

Example: IPO TableExample: IPO Table

/*

* A C program example

*/

#include <stdio.h>

main()

{

SUM = 7 + 8 + 3 + 2 + 1;

printf(³The sum is %d³,

SUM);

}



Program CompilationProgram Compilation

Checks that there is no violation of programming

language

Compiler

reads entire source code the converts it to object code,

which then it is now executed by the computer

Interpreter

reads source code one line at a time, and perform the

specific instruction contained in one line



Compilers & InterpretersCompilers & Interpreters

A compiler translates all of the source

code into object code, an executable

program. During this translation process,

a program listing of any syntax errors is

produced.

An interpreter translates one line of thesource code at a time. Interpreters run

programs more slowly than compilers,

but they are helpful programs for finding

syntax errors, because they are

interactive.



Running Testing and DebuggingRunning Testing and Debugging

Check and corrects errors

Types of errors

Syntactical / Logical Errors

Compile-time /R

un-time Errors



DocumentationDocumentation

Syntactical / Logical Errors Syntactical errors

are due failure from ff the syntax

Syntax grammatical rules of the language defining its legal constructs

Logical Errors formulation of algorithms, wrong analysis / approach

Compile / Run-time Errors Compile-time

halt compilations

Compilation method in translating program codes into machine codes

Note: syntax error encountered during compilation is a compile-timeerror

Run-time error appears during execution or the program



DocumentationDocumentation

includes the pictorial and written descriptions of the software.

It contains internal descriptions of programming commands

and external descriptions and instructions.

Problem definition, algorithms, error-free source code, testing

procedures

Documentation is necessary since, sooner or later, the

program will need to be maintained (correct bugs, add new

features, handle problems not thought of previously, etc. This

is very difficult without documentation

Examples

books, manuals, and pamphlets



ProblemProblem--solving approach like algebrasolving approach like algebraclassclass

How fast is a car traveling if it goes 50 miles in 2

hours?

Output: a number giving the rate of speed in miles

per hour

Input: the distance and time the car has traveled

Process: rate = distance/time



Pictorial representation of the problemPictorial representation of the problemsolving processsolving process



Program PlanningProgram Planning

A recipe is a good example of a plan

Ingredients and amounts are determined bywhat you want to bake

Ingredients are input

The way you combine them is the processing What is baked is the output



Program Planning TipsProgram Planning Tips

Always have a plan before trying to write a

program

The more complicated the problem, the

more complex the plan must be

Planning and testing before coding saves

time coding



Program development cyclProgram development cyclee

1. Analyze: Define the problem.

2. Design: Plan the solution to the problem.

3. Choose t he interface: Select the objects

(text boxes, buttons, etc.).



Program development cycleProgram development cyclecontinuedcontinued

4. Cod e: Translate the algorithm into aprogramming language.

5. T est and d ebug : Locate and remove anyerrors in the program.

6. Complete t he docu mentati on: Organize allthe material that describes the program.



2.2 Programming Tools2.2 Programming Tools

Three tools used to convert algorithms intocomputer programs:

Flowcharts - Graphically depict the logical steps to carry out atask and show how the steps relate to each other.

Pseudocode - Uses English-like phrases with some VB.NET

terms to outline the program. Hierarchy charts - Show how the different parts of a program

relate to each other.



Algorithms Algorithms

A step by step series of instructions for solving a

problem (a recipe is an example of an algorithm)



Problem solving exampleProblem solving example

How many stamps do you use when mailing a

letter?

One rule of thumb is to use one stamp for every five

sheets of paper or fraction thereof.



Algorithm Algorithm

1. Request the number of sheets of paper; call it

Sheets. ( input )

2. Divide Sheets by 5. ( processing )

3. Round the quotient up to the next highest whole

number; call it Stamps. ( processing )

4. Reply with the number Stamps. ( output )



FlowchartsFlowcharts

Graphically depict the logical steps to carry out a

task and show how the steps relate to each other.



Flowchart symbolsFlowchart symbols



Flowchart symbols continuedFlowchart symbols continued



FlowchartFlowchartexampleexample



PseudocodePseudocode

Uses English-like phrases with some VB terms to

outline the task.





HierarchyHierarchy chartscharts

Show how the different parts of a program relate to each other

Hierarchy charts may also be called

structure charts

HIPO (Hierarchy plus Input-Process-Output) charts

top-down charts VTOC (Visual Table of Contents) charts



Hierarchy charts exampleHierarchy charts example

Each entryrepresents a

module



DivideDivide--andand--conquer conquer methodmethod

Used in problem solving ± take a large problem and

break it into smaller problems solving the small

ones first

Breaks a problem down into modules



Statement structureStatement structure

Sequence ± follow instructions from one line to the next

without skipping over any lines

Decision - if the answer to a question is ³Yes´ then one

group of instructions is executed. If the answer is ³No,´ then

another is executed

Looping ± a series of instructions are executed over and

over



SequenceSequenceflow chartflow chart



Decision flow chartDecision flow chart



Looping flow chartLooping flow chart



Direction of Numbered NYC StreetsDirection of Numbered NYC Streets Algorithm Algorithm

P r oblem: Given a street number of a one-way

street in New York, decide the direction of the

street, either eastbound or westbound

Discussi on: in New York even numbered streets

are Eastbound, odd numbered streets areWestbound



FlowchartFlowchart




Program: Determine the direction of a numbered NYC street

Get street

If street is even Then

Display Eastbound

ElseDisplay Westbound

End If



Hierarchy ChartHierarchy Chart



Class Average AlgorithmClass Average Algorithm

P r oblem: Calculate and report the grade-point average for aclass

Discussi on: The average grade equals the sum of all gradesdivided by the number of students

O ut put: Average grade

In put: Student gradesP r ocessing: Find the sum of the grades; count the number of

students; calculate average



FlowchartFlowchart




P r ogram: Determine the average grade of a class

Initialize Counter and Sum to 0

Do While there are more data

Get the next Grade

Add the Grade to the Sum

Increment the Counter

Loop

Computer Average = Sum/Counter

Display Average



Hierarchy ChartHierarchy Chart



PseudocodePseudocode & Algorithm& Algorithm

Example 1: Write an algorithm to determine a

student¶s final grade and indicate whether it is

passing or failing. The final grade is calculated as

the average of four marks.



PseudocodePseudocode & Algorithm& Algorithm

Pseudocode:

I nput a set of 4 marks

Calculate their average by summing and dividing by 4

if average is below 50

P rint ³FAIL´

else

P rint ³ P ASS ́



The FlowchartThe Flowchart

A Flowchart

shows logic of an algorithm

emphasizes individual steps and their

interconnections

e.g. control flow from one action to the next



Flowchart SymbolsFlowchart Symbols

Basic





Example 2Example 2

Algorithm

Step 1: Input Lft

Step 2: Lcmn Lft x 30

Step 3: Print Lcm

START

InputLft

Lcmn Lft x 30

Print

Lcm

STOP

Flowchart

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1) Introduction to Computer Programming