02-Overview of C++ (Part 1)

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Data Structures

Overview of C++ (part 1)


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CT077-3-2-DSTR Data Structures 2

Learning Objective

At the end of the lecture, you should be able to know:

the basic components of a C++ program

how to write a simple C++ program and use

preprocessor directives how to use input\output in a program

the selection control structures if, if...else, and

switch in a program the repetition (looping) control structures

how to write and use a simple function


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Creating a C++ Program

A C++ program has two parts:

Preprocessor directives

The program statements (functions, classes, and

types definitions)

Preprocessor directives and program statements

constitute C++ source code (in .cpp and .h files)

Compiler generates object code (.obj) and a process

called Linking generates executable file (.exe on

windows)


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A simple C++ program can be a collection of

functions, one of which is the function main

The first line of the function main is called theheading of the function:

void main()

The statements enclosed between the curly

braces ({and }) form the body of the function

int main () {

//mandatory by some compilers

return 0; //or other int value

}


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Syntax to include a header file:

For example:

#include

Causes the preprocessor to include the

header file iostream in the program


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cinand coutare declared in the header file

iostream, but within stdnamespace

To use cinand coutin a program, use the

following two statements:

#include

using namespacestd;

Without using std namespace, you must use scope

operator :: to write fully qualified names (std::cinand

std::cout)




To use the string type, you need to access its

definition from the header file string

Include the following preprocessor directive:

#include




Sample Run:

Line 9: firstNum = 18

Line 10: Enter an integer: 15

Line 13: secondNum = 15

Line 15: The new value of firstNum = 60



Programming Example

Write a program that takes a given length as input

expressed in feet and inches. Convert and output

the length in centimeters

Convert the length in feet and inches to all

inches:

Multiply the number of feet by 12

Use the conversion formula (1 inch = 2.54

centimeters) to find the equivalent length in

centimeters



Programming Example



Programming Example

Sample Run:

Enter two integers, one for feet, one for inches: 15 7

The numbers you entered are 15 for feet and 7 for inches.The total number of inches = 187

The number of centimeters = 474.98



Selection Control

One-Way Selection

Two-Way Selection

Multiple Selections: Nested if

Conditions evaluation to true and false

Multiple Selections: switch Statement



One-Way Selection

The syntax of one-way selection is:

The statement is executed if the value of theexpression evaluates to true

The statement is bypassed if the value is false;

program goes to the next statement ifis a reserved word



Two-Way Selection

Two-way selection takes the form:

If expression is true, statement1 is executed;

otherwise, statement2 is executed

statement1 and statement2 are any C++statements

elseis a reserved word



Multiple Selections: Nested if

Nesting: one control statement in another

To test more than one condition, an ifstatement

can be nested inside another ifstatement


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Conditions Evaluation

Beware that in C and C++, any value evaluated

to zerois considered to be false, and any other

value is treated as true

This can help write short code, but may lead tobugs which are very difficult to detect:

char c = 'Y';

while(c = 'Y') {

//do something here

cout > c;

} //why doesn't my loop ever end?

This is an assignment operator, not checking equality

operator. The code compiles without a problem because

any value is evaluated as a condition, and this

expression evaluates to true always ('Y' is not zero) !!


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switch Structures

switch structure: alternate to

if-else

Value of the expression

determines whichcorresponding action is taken

Expression is sometimes

called the selector


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switch Structures

One or more statements may

follow a case label

The breakstatement may or

may not appear after eachstatement

switch, case, break, and

defaultare reserved words


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switch Structures


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Repetition Control

Repetition control structure causes a statement

or group of statements to be repeated

Repetition allows you to efficiently use variables

For example, to add five numbers: Declare a variable for each number, input the

numbers and add the variables together

Create a loop that reads a number into avariable and adds it to a variable that contains

the sum of the numbers


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while Loop

The general form of the whilestatement is:

Statement can be simple or compound

Expression acts as a decision maker and is

usually a logical expression

whileis a reserved word


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while Loop


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Case 1: Counter-Controlled Loops

If you know exactly how many pieces of data

need to be read, the whileloop becomes a

counter-controlled loop


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Case 2: Sentinel-Controlled Loops

Sentinel variable is tested in the condition

and loop ends when sentinel is encountered


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Case 3: Flag-Controlled Loops

A flag-controlled while loop uses a bool variable

to control the loop


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for Loop

The general form of the forstatement is:

The initial statement, loop condition, andupdate statement are called forloop control

statements

foris a reserved word


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dowhile Loop

General form of a do...while:

The statement executes first, and then the

expression is evaluated

To avoid an infinite loop, body must contain astatement that makes the expression false

Loop always iterates at least once


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dowhile Loop


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Choosing the Right Looping

Structure

All three loops have their place in C++

If you know or can determine in advance the

number of repetitions needed, the forloop is

the best choice

If you do not know and cannot determine in

advance the number of repetitions needed,

and it could be zero, use a whileloop If you do not know and cannot determine in

advance the number of repetitions needed,

and it is at least one, use a do...while loop


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User-Defined Functions

A function is defined in C++ in a very similar way

as in Java

A function can exist outside a class definition

General syntax:

functionType can be void, and a function may have no

parameter list at all

A function prototype is useful, and may be

necessary at some cases


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Function Prototype

Function prototype: function heading without the

body of the function

Syntax:

It is not necessary to specify the variable name

in the parameter list The data type of each parameter must be

specified


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Function Example


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Function Example


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User-Defined Functions

By default, parameters are passed by value

Values that are passed when you call a function get

copied, and any change to the parameters inside the

function are not carried out on original passed-in

parameters of the function call

We will learn how to pass parameters by pointer and

by reference in order to change them, or avoid copying

Write a int max (int a, int b)function and test it

Write a void changeMe(int v)function and test it


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Further Reading

NTUs C++ Programming Tutorial

The Process of Writing a C++ Program

www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_I

ntroduction.html

Check this article on some common mistakes in

C\C++ programming

8 Common Programming Mistakes:

www.cprogramming.com/tutorial/common.html
http://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www.cprogramming.com/tutorial/common.htmlhttp://www.cprogramming.com/tutorial/common.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.htmlhttp://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp0_Introduction.html


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What we will cover next

Overview of C++

Simple Data Types

Arrays

Passing parameters to functions

Passing arrays to functions

02-Overview of C++ (Part 1)

Documents

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