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AACS1074 Programming Concepts and Design IChapter 1: Introduction to C

Chapter 1:

Introduction to C


1.1 Introduction to Computers

Overview of computer system:

Computer System

SoftwareHardware

The physical equipments. E.g. keyboard, mouse, monitor, processor, memory, etc.

Collection of programs that tell hardware how to perform tasks.



2 categories of computer software:

Computer System

SoftwareHardware

SystemSoftware

ApplicationSoftware

Programs that manage computer resources.

Programs that help users to solve their problems.



System software and application software:

Computer System

SoftwareHardware

SystemSoftware

ApplicationSoftware

OperatingSystem

SystemSupportSoftware

SystemDevelopment

Software

General-PurposeSoftware

Application-SpecificSoftware


Example of system software:

UNIX, Linux, MS Windows, Mac OS, etc.

Disk defragmenter, screen saver, antivirus tool, etc.

Programs that creates programs.

MS Visual C++ 6.0, MS Visual Studio 2008, Java NetBeans, etc.

OperatingSystem

SystemSupportSoftware

SystemDevelopment

Software


Example of application software:

MS Word 2007, Windows Media Player, Window Live Messenger, etc.

LRT ticketing system, hotel reservation system, payroll system, etc.

General-PurposeSoftware

Application-SpecificSoftware


1.2 Computer Languages

Program: A set of instructions that tell computer how to perform tasks.

We use a computer / programming language to write program.

Categories of computer languages:

Machine languages

Symbolic languages

High-level languages


Evolution of computer languages:


Program in machine language:


Machine Language

Use binary codes (0s and 1s).

The only language computer can understand.

Platform-dependent.

Very hard to program.

100100100011010110101110


Program in symbolic language:


Symbolic Language

a.k.a. assembly language.

Use symbolic codes, mnemonics and meaningful abbreviations.

Platform-dependent.

Easier to program.

E.g. MASM 6.15, Turbo Assembler, etc.


Wait a minute…

Since computers only understand machine language. Then, how computers recognize other computer languages such as symbolic language?

?


Translate it!!!

Programmer writes a program using preferable programming language. Finally, translate it into machine language by using a translator and the program is ready to run!!!

SourceProgram Translator

100010111100110100110011

Machine Language


Assembler

Symbolic language has to be translated to machine language before it can be run.

Translator: assembler.

Symbolic Language

Machine Language

Assembler

Source Program Translator 0s and 1s


Example of high-level language:


High-Level Language

a.k.a procedural language.

Use English-like codes and mathematical operators.

Platform-independent.

Very easy to program.

E.g. C, Pascal, etc.


Compiler / interpreter

High-level language has to be translated to machine language before it can be run.

Translator: compiler / interpreter.

High-Level Language

Machine Language

Compiler / Interpreter

Source Program Translator 0s and 1s


The Compilation Process

Compiler converts source program into object program (machine language version).

If encounters error, program error listing is shown.

Object program is then loaded and run.

CompilerObject

ProgramResults

ProgramError

Listing

Data

SourceProgram

Machine LanguageTranslator


1.3 Introduction to C

C is a high-level language.

For systems and applications programming.

Portable / platform-independent: run at other platforms with no or little alterations.


Exercise 1.1

By following the instructions giving by your lecturer, write, compile and run your first C program – the Hello World program!

#include <stdio.h>

int main(void){ printf("Hello World!\n"); return 0;}


Exercise 1.2

Create a new program that display the following lyrics on screen:

Welcome, welcome all of youGlad you are with usShake hands, no need to be blueWelcome to you!


1.4 Program Development

To develop a program, programmer must complete the following steps:

Understand the problem

Develop a solution

Write the program

Test the program


Take time to understand the problem and design the solution, before you code the actual program.

This reduce the chances of misunderstanding and errors. Hence, the final program can be implemented in a shorter time and with a better quality.

An old programming proverb:

Resist the temptation to code!!!


Program Development


Carefully study the user requirements.

Understand what he wants the program to do and what kind of output he wants to have.

Develop a solution


Write the program

Test the program


Program Development

Develop a solution

Design the logic of the program by using tools such as:

Structure chart

Pseudocode

Flowchart

Develop a solution


Write the program

Test the program

We will talk about them later.


Program Development

Write the program

Code the actual program by using the preferable programming language.

Develop a solution


Write the program

Test the program


Program Development

Test the program

Run and test the program to ensure it is free of logical errors.

Develop a solution


Write the program

Test the program


Example 1.1

You would like to install new floor covering in your home and would like to calculate the cost that would be involved. Your plan is as follows:

Only the living space will be carpeted. The garage and closets will not be considered.

The kitchen and bathrooms will be covered with linoleum. The rest of the house is to be carpeted.


You need a computer program to compute the flooring cost. How should you approach this problem?


A big programming problem.

Divide and Conquer!!!


Break down the task into a few big subtasks.



Decompose each big subtask into smaller subtasks.



Further break down each smaller subtask into even smaller subtasks.



Eventually the subtasks become so small that they are trivial to implement in C language.




a.k.a. stepwise refinement or top-down design.


Tool: Structure Chart

A hierarchy chart that shows the functional flow through the program.

Shows how the program is broken into logical steps. Each step will be a separate module.


A structure chart:


Tool: Pseudocode

Use English words to convey program logic.

Contains the logical steps / algorithms to accomplish the task.


A pseudocode:


Tool: Flowchart

Use standard graphical symbols to represent the logical flow of data through a program.

[ show flowchart ]


Flowchart Symbols

Input/Output Processing Module

Decision FlowlinesTerminal

Off-page Connector

On-pageConnector


Example 1.2

Problem: Calculate the sum of 2 numbers.

Hint: The general algorithm for a programming problem is normally:

Get the data

Perform the computations

Display the results


Example 1.2: Structure chart

Sum Two Numbers

Get User Input

Calculate Sum

Display Sum


Example 1.2: Pseudocode

START Prompt and read number1 Prompt and read number2 sum = number1 + number2 Display sumEND


Example 1.2: Flowchart

START

END

Read number1

Read number2

sum =number1 + number2

Display sum


Exercise 1.3

By using structure chart, pseudocode and flowchart, design the solution for a program that reads three (3) numbers from user, calculates their total and average, and displays the calculated total and average on the screen.

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Sports

program page

program development

program code

actual program

new program

final program

computer languages program

pagesource program translator