Chapter 1 Introductionc

CHAPTER 1CHAPTER 1INTRODUCTIONINTRODUCTION

INTRODUCTION TO INTRODUCTION TO COMPUTER COMPUTER

PROGRAMMINGPROGRAMMING(CSC425)(CSC425)

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CONTENTS

CHAPTER 1 : Introduction To Computer Programs

• A Brief History of the C++ LanguageGeneration of Programming LanguageWhat is a computerHardware and Software of a computer What is a computer programTranslation using Compilers or Interpreters

• Preparation for Programming

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CSC425 : INTRODUCTION TO COMPUTER PROGRAMMING

A BRIEF HISTORY OF THE C++ LANGUAGE

The C++ Programming Language is basically an extension of the C Programming Language.

C is a programming language which born at “AT & T’s Bell Laboratories” of USA in 1972. It was written by Dennis Ritchie.

This language was created for a specific purpose: to design the UNIX operating system (which is used

on many computers). From the beginning, C was intended to be useful--to

allow busy programmers to get things done. C++ is the new improved version of C for the

latest programming needs. It contains everything C does, plus new additions for OOP concept.

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3GL

4GL

5GL

Machine LanguageMachine Language

Assembly LanguageAssembly Language

High-Level LanguageHigh-Level Language Se

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Generation of Programming Language

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Machine Language (1940s – 1950s)Machine Language (1940s – 1950s)

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Lowest level of language

Represent data and program instructions as 1s and 0s

The only language that computer directly understand.

(Do not require translator)

Not convenient to read and use.

First generation language

Machine - dependent

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Assembly Language (1950s – 1960s)Assembly Language (1950s – 1960s)

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Second generation language Developed to replace 1s and 0s use in machine language. Use mnemonic codes : abbreviations that easy to remember

A for AddA for Add

C for CompareC for Compare

MP for MultiplyMP for Multiply

Requires a translator to translate the assembly program into machine language ( assembler).

Difficult to learn Machine-dependent

The difference between Machine Language and

Assembly Language

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Memory Address Machine-Language Instructions

Assembly-Language Instructions

00000000 00000000 CLA

00000001 00010101 ADD A

00000010 00010110 ADD B

00000011 00110101 STA A

A Machine-language Program Fragment and Its Assembly-Language Equivalent


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High Level LanguageHigh Level Language

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Made easy for programmer to develop and maintain program

Machine- independent (can run on may different types of computers)

Have 3 categories : third, fourth and fifth generation

Written in series of English-like words

Must be translated to machine code first. (Use translator)


High-level languages

Language Application Area Origin Name

FORTRAN Scientific Programming Formula Translation

COBOL Business data Processing Common Business-Oriented Language

Lisp Artificial Intelligent List processing

C System Programming Predecessor Language was named B

Prolog Artificial Intelligent Logic Programming

C++ Support objects and object oriented programming

Incremental modification of C (++ is the C incremental operator)

Java Supports Web Programming Originally name “Oak”

9CSC425 : INTRODUCTION TO COMPUTER PROGRAMMING

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3rd Generation Language (1960 – 1970)3rd Generation Language (1960 – 1970) Instruction is written as a series of English-like

words. Often are called procedural languages Translation is performed using compiler or

translator Example of 3GL programming language:

FORTRAN, COBOL and BASIC


11Example coding in FORTRAN

FFOORRTTRRAANN

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FORTRAN Stands for FORmula TRANslator Develop in the late 1950s by team of IBM Designed for scientific applications Used most often by scientist, engineers and mathematicians.

Generation of Programming LanguageHigh Level LanguageHigh Level Language

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COBOL Common Business Oriented Language was developed in the early 1960s more widely used used for business applications easy to read, write and maintain


BASIC Was develop in the mid - 1960s by John Kemeny and Thomas

Kurtz

Easy to learn and used

Widely used for education and business application.


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4th Generation Language (1970 – 1980s)4th Generation Language (1970 – 1980s) Also uses English-like statements Non- procedural languages

only to specify what is to be accomplished without explaining how

Coding programs requires less time and effort Example of programming language

PROLOG, FOCUS, LISP and FORTH


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5th Generation Language (1990s)5th Generation Language (1990s) Also called natural language. A type of query language that allows the user to

enter requests that resemble human speech. Translate human instructions into code the

computer understands. Sometimes referred to as knowledge-based

language.


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Example of Natural language

Welcome to Inquiry

What would you like to know?

Do we have hammer #37645?

One moment please..Yes, we have 14 hammer #37645.Do we have 1 box nails #3601?

One moment, please.No nails #3601 in stock.

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Language TranslatorS

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AssemblerAssembler Used in assembly language for translate the

language to machine language

Program need to translate because computer only understand machine language.

Three kind of translator :1. Assembler2. Interpreter 3. Compiler

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Sourceprogram

Data

INTERPRETER RESULTS

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InterpreterInterpreter A set of program that executes the instructions as they

were translated. Interpreter executes a program from its high-level form.

Translates one program code statement at a time. Immediately displays feedback when it finds error. Use for Basic

Language Translator

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Sourceprogram

Data

COMPILER RESULTSOBJECT

PROGRAM

ProgramListing

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CompilerCompiler A program that translates a high-level language program

into machine language as a complete unit Translating the source code from its original language

into machine code. Converts the entire source program into machine

language at one time Use for C, C++ and Cobol

Language Translator

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Programming Approach

2 typesStructured Object -oriented

1.1. Structured ProgrammingStructured Programming

A methodology in which all program logic is constructed from a combination of three control structures : sequence, selection and repetition (loop)

Program logic is description of the step-by step procedures for a module.

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data - called attributes or variablesprocedure - the instructions that tell the data what to do

- called operations or method.

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Programming Approach

2.2. Object-oriented programmingObject-oriented programming

Packaged the data and procedure into a single unit called an object which can be reused and modified.

Object have classes and subclasses.

Each class contains the characteristics that are unique to objects of that class.

PREPARATION FOR PROGRAMMING

Reason for studying concepts of programming languages :1. Increased capacity to express ideas and

solve problems. Studying programming languages may increase

the capacity and ability of students to express their ideas in a formal, computational form.

2. Increased ability to automate process Programs are built mainly so that simple, or even

complicated processes to be executed automatically.

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Computer programming

Craft of developing a computer program. Require knowledge, skill and creativity. Both skill and knowledge in problem

solving and programming language.


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Computer program Hanly [2001], “List of instructions that direct the computer

to transform information from one form to another.” Information refers to the contains of specific memory

location. It is written using programming language. Turn data (input) into useful information (output). Program uses variables to store data


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ProgramInput Output

StorageExampleExample

Source file A file containing a program written in a high-

level language; the input for the compiler Syntax

Grammar rules of programming language Object file

File of machine-language instructions that is the output of a compiler

Algorithm A precise step-by-step action to perform

overall task of the program.

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Basic Concepts


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Basic Concepts

Compilation Process

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CompilerSource File Object File

(Input) (Output)


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Problem Analysis

Programs Modelling

Coding Programs

Testing and Debugging

Maintenance

DOCUMENTATION

PROGRAM DEVELOPMENT LIFE CYCLE

PROGRAM DEVELOPMENT LIFE CYCLE Computer programming is a process to

develop a computer program. 5 steps:

1. Problem analysis,2. Program design, 3. Coding,4. Testing and debugging, and 5. Documentation and Maintenance


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A process of identifying the output, processes and input of a program.

How to identify output? Nouns and adjectives

Keywords – print, display, produce How to identify input?

Nouns and adjectives Keywords – accept, enter, receive, read

Define the storage (variable) and data type to hold data Outline the process

Arithmetic or logic operation Input-Process-Output (IPO) chart as tool

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Problem Analysis


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Input Process Output

Defining the problem Identify :

1. Input ( given data)2. Output ( the result)3. Process relation between input and outputusing formula

Problem Analysis


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Example 1

Write a program that can input 3 integer number from user. Find the average for the number. Display all the numbers and the average

Problem analysis

Input : 3 numbers

Process : 1. Total up 3 numbers

2. Divide the number by 3

Output : 3 numbers and the average

Problem Analysis


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Example 2 Evaluate the following problem statement and

identify the input and output.

Nation’s Air force has asked you to write a program to label supersonic aircraft as military or civilian. Your program is to be given the plane’s observed speed in km/h and its estimated length in meters. For planes traveling in excess of 1100km/h, you will label those longer than 52 meters “civilian” and shorter aircraft as “military”. For planes traveling at slower speeds, you will issue an “aircraft type unknown” message.

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Problem Analysis


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Input-Process-Output (IPO) chart

INPUT PROCESSING OUTPUT

speed length

Validate the speed and length

• Speed >1100km/h AND length > 52m

• Speed > 1100km/h AND length <= 52m

• Speed <= 1100km/h

Classification

Can be one if the following values

Civilian

Military

Aircraft type unknown

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Problem Analysis


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Program Design

Planning the solution to a problem Developing an algorithm

Algorithm is a precise step-by-step action to perform overall task of the program.

Can be represented either using flowchart or pseudo-code

Tools used for Program Design are:- Pseudo Code Flow Chart


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Flow chart

A set of symbols and edges used in flow chart:

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Terminal (Begin and End)

To represent the process

Input/Output Operation

Condition/Evaluation

Direction

ExampleExampleCSC425 : INTRODUCTION TO COMPUTER PROGRAMMING

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1. Set sum = 0, avg = 02. Read 3 integer number3. Total up 3 integer number

sum = a+b+c4. Find the average

avg = sum / 35. Display 3 integer number and average

algorithm

Program Design

Example to get average of 3 numbers.


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Flowchart

Pseudocode

START INPUT a,b,c sum = a+b+c avg = sum / 3 PRINT a,b,c PRINT avgEND

Refer to Example Average


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Program Design

Refer to Example Aircraft

STARTREADSpeed, LengthIF Speed > 1100 FALSE - Classification = “Aircraft Type Unknown”TRUE - Length > 52FALSE - Classification = “Military”TRUE Classification = “Civillian”

END


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Program Design


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Program DesignRefer to Example Aircraft

Desk-Check the algorithm

Speed Length Classification

11701180900800

35566634

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Program Design


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Refer to Example Aircraft

Implement the flowchart or pseudo code into specific programming language rules (syntax) Identify the storage requirement

Compilation Express solution in a programming language Translate the logic from the flowchart or pseudocode. There are many programming languages : BASIC,

COBOL, Pascal, Fortran, C, C++, Java etc Each language has it’s own syntax (rules of

language)

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Source CodeSource Code

Coding


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Refer to Example Average

Coding in C++ Language

Output of the program

Coding


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Testing and Debugging Program must be freed from syntax error Use a set of test data to validate the output.

Program must produce receive valid input and produce correct output.

Program must handle invalid input efficiently. Does the program accept out of range value? Trace error either syntax or logic error

1. Testing running the program with a set of data

2. Debugging Trace and fixed the error


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Testing and Debugging Three types of error:

1. Syntax error2. Logic error3. Run-time error

Syntax error Occurs when not applied the rules of the language. Can be traced by the compiler during compilation Also called as “compile-time error“compile-time error”


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Testing and Debugging

Logic error Error in logic of processing Cannot be traced by the compiler

Output produced is wrong

Run-time error

errors caused program instructions that require the computer to do something illegal such as an attempt to divide a number by 0.

program will stop automatically and display a certain messages.


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Documentation and MaintenanceDocumentation User manual Written detailed description of the program cycle and

specific facts about the program Documentation materials include :

1. Description of the program

2. Logic tools : flowcharts, pseudocode

3. Data- record descriptions

4. Program listing

5. Testing results

6. Comments Program description capability, limitation, user guide


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Documentation and Maintenance

Maintenance Modification made to the finished program Software to meet current requirement Need to refer the previous documentation


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A good program

must have

AccuracyAccuracy

ReliabilityReliability

EfficiencyEfficiency

MaintainabilityMaintainability

ReadabilityReadability

UsabilityUsability


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SELF EXERCISE

1. Write a flow chart to calculate and display an average of three numbers using sequential design

2. Rewrite the above design, determine whether the average is higher than 50 or not. Display the appropriate message for each case.

3. Rewrite problem 1 using iteration any iteration approach.

4. Write a flow chart to calculate an average score of 20 students.

5. Write a flow chart to calculate an average of a series positive numbers. The process will stop if number entered has a negative value.

6. The cost to send a telegram to UK is RM15.50 for the first 15 letters and RM0.50 for the subsequent letters. Draw a flowchart to calculate the cost of sending the telegram. 48CSC425 :

INTRODUCTION TO COMPUTER PROGRAMMING

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Chapter 1 Introductionc

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