8.3 program structure (1 hour)

8.3 Introduction to C++8.3 Introduction to C++

8.3.1 Program Structure8.3.1 Program Structure

8.3.2 Using Compiler8.3.2 Using Compiler


• Learning Outcome– Identify the component of C++

i. comment

ii. preprocessor directive

iii. function

iv. body

v. return statement

8.3.1 Program Structure8.3.1 Program Structure• A computer program consists a list of

instructions written in a computer language.//This is my first C++ program //It prints a line of text

#include <iostream.h>#include <stdlib.h>

int main()

{ cout << "My first C++ program" ;

system("PAUSE"); return 0;}

i. comment


iii. function

iv. body

v. return statement Fig. 1 : Example 1

8.3.1 Program Structure8.3.1 Program Structure// height.cpp // Convert height in feet to inches

#include <iostream.h>#include <stdlib.h>

int main()

{ int feet, inches;

inches = feet * 12;cout << “Enter feet value : ”;cin >> feet;cout << “Height is“ << inches ;cout << “in.” ;

system("PAUSE"); return 0;}

i. comment


iii. function

iv. body

v. return statement Fig. 2: Example 2

8.3.1 Program Structure8.3.1 Program Structure• comment //This is my first C++ program //It prints a line of text

/*This is my first C++ program It prints a line of text */

• Style to insert a comment in C++.– Text begin with two double slash (//) -

normally used for single line comment– Text begin with /* and ends with */ - possibly

containing many lines

8.3.1 Program Structure8.3.1 Program Structurei. comment

• The purpose to insert a comment– To document a program– To improve program readability – help other

people read and understand a program.

• Remember – comment do not cause the computer to perform any action when the program is run.


i. preprocessor directive

- Preprocessor directive is a general instruction to the C++ compiler

- # :are processed by preprocessor before program is compiled.

- #include <iostream.h> :tells the preprocessor to include in the program the contents of the input/output stream header file iostream.h

8.3.1 Program Structure8.3.1 Program Structurei. preprocessor directive

- iostream.h

:specific file needed for programs that either input data from keyboard or write output on the screen.

:called as header file ( with the file extension .h)

:other examples

:#include <stdlib.h>

:#include <math.h>

8.3.1 Program Structure8.3.1 Program Structurei. function

int main()

: the parentheses, () after main indicate that main is a program building block called a function.

: example given on Fig. 1; contain only one function.

: C++ programs normally begin executing at function main.


i. Body

: the left brace, {, must begin the body of every function.

: a corresponding right brace, }, must end the body of each function.

: examples: Refer to Fig.1 and Fig.2 ( body segment )


i. Body

: The body of main may consist of:

i) variable declaration and reserve word

e.g. : int feet, inches; reserved word variables

8.3.1 Program Structure8.3.1 Program Structurei. Body


ii) inputinput / output consoleconsole

input console: use standard input stream object - cin and input operator, >>, to allow user type in a value (or values)

e.g. : cin >> feet;

8.3.1 Program Structure8.3.1 Program Structurei. Body


ii) input / output consoleoutput console

output console: use use standard output stream object - cout and the output operator, <<, to output the message.

e.g. : cout << “Height is“ <<inches;


i. Body


iii) C++ statement

: Every statement must end must end with semicolon (;).

e.g. :

i. cout <<"My first C++ program”;

ii. inches = feet * 12;


i. return statement

return 0;

: is included at the end of main function.

: the C++ keyword return statement is used at the end of main, the value 0 indicates that the program has terminated successfully.

:the right brace,}, indicates the end of main.


• Learning Outcome– Edit– Compile– Link– Execute program


program.cpp (C++ source code)

C++ compiler

program.obj (object code)

C++ Library

Linker

program.exe(executable program)

Fig. 1: Building a C++ Program


• EditEdit – enter the program statemententer the program statement• To write a C++ program, you need to enter the

program statements by using:– Text editor (e.g. Notepad, Microsoft Word etc.) – Integrated Development Environment (IDE)(e.g.

Dev C++, Borland C++ etc.)

• The complete program statements called “source codesource code”.


• CompilCompile – translating C++ into machine code translating C++ into machine code (also called “object code”) – Compiler determines the syntax error.

• Link Link – Run the Run the linkerlinker – combine the machine code with code from C++ library; after compiles is successful.


• Execute Program Execute Program – an application can be run.an application can be run. – Finally, the computer, under the control of its

CPU, executes the program one instruction at a time.

Remember : Remember :

Compiler detects grammatical (syntax) error NOT the program-logic error


Editor

Compiler

Linker

Run

Link

Compile

EditSource code

Object code

Executable image

Result / Output

ToolTool StepStep ProductProduct

Technology

8.3 program structure (1 hour)