Arash Rafiey TA : Xu Cheng Office Hours M-W 10:30 – 11:30

How Create a C++ Program

#include using namespace std; void main() { cout<<“Hello World”; } If your compiler gives error then

#include void main() { cout<<“Hello World”; cout<<endl; // for going to new line cout<<“ good bye”; } cout is an object for printing out some thing on the screen.

#include void main() { cout<<“Hello World \n”; cout<<“ good bye”; } we can use \n instead of cout<<endl;

How to run your program Using Linux or unix: g++ myFile.cpp./a.out g++ myFile.cpp myFile.out./myFile.out

Declare Statement & Variable Each variable must be declare before use Each variable has a type: For example int, char, float. int for Integer type; char for character like ‘A’; float for real number;

Example int LuckyNumber=17; float RealNumber; char a=‘A’;

Identifiers Identifier: name of a variable, function, or class Rules for identifiers in C++: 1 Can be made up of letters, digits, and the underscore (_) character 2 Cannot start with a digit 3 Cannot use other symbols such as ? or % 4 Spaces are not permitted inside identifiers 5 You cannot use reserved words 6 They are case sensitive

Self Check 1. What is the type of the values 0 and ‘0’? 2. Which of the following are legal identifiers? Greeting1 g void 101dalmatians Hello, World

Answer int and char Only the first two are legal identifiers

Syntax : Variable Definition typeName variableName = value; or typeName variableName; Example : int numbe = 12; Purpose: To define a new variable of a particular type and optionally supply an initial value

The Assignment Operator Assignment operator: = Not used as a statement about equality Used to change the value of a variable int number1; int number2, number3; number1=number2=number3=88;

number2=number2-1; number3=number2+1;

How to read a variable #include using namespace std; void main() { int number; cout<<“please enter a number \n”; cin>>number; number=number+1; cout<<“the number is “<<number; }

Integer Types The short, int and long Integer Types A short integer is at least 16 bits A int integer is at least as big as short A long integer is at least 32 bits and at least as big as int.

E.g. A 16-bit int might run from to The sizeof operator returns the size (in bytes)

#include int main() { int n_int = INT_MAX; short n_short = SHRT_MAX; long n_long = LONG_MAX; cout << “int is “ << sizeof (int) << “ bytes” << endl; cout << “short: “ << n_short << endl; cout << “long: “ << n_long << endl; return 0; }

int is 4 bytes Maximum values: –Short: –Long:

Characters and small integers #include int main() { char ch = ‘M’; // assign ASCII code int a = ch; cout << “ASCII code: “ << ch << “ is “ << a << endl; ch = ch + 1; a = ch; cout << “ASCII code: “ << ch << “ is “ << a << endl; return 0; }

Output M is 77 N is 78

Boolean type bool isReady = true; int ans = true; // ans assigned 1 int promise = false; // promise assigned 0 bool start = -100; // true bool stop = 0; // false

Floating-point number E.g We have float, double, long double

Arithmetic operators Summation: + Multiplication: * Division: / Subtraction: -

Operator Precedence int number = * 5 // 35 or 23? float logs = 120 / 4 * 5 // 150 or 6??

Type Casting Conversion between types: (typeName) value // c typeName (value) // c++ e.g. – cout << int(‘A’) << endl; // 65 – float one, –int two; one = ; two = (int) (int) 2.1;

Functions Building blocks of programs A function –Has an input and an output –Contains a set of instructions x = sqrt(16); // returns 4

Syntax typeName functionName (typeName varName_1, …) { BODY. return value; }

Examples of functions int sum (int firstValue, int secondValue) { int final; final = firstValue + secondValue; return final; } void main() { int a = 1; int b = 2; int total = sum(a,b); cout << “Total is: “ << total << endl; }

Arrays An array is a data form that holds several values of the same type Syntax: –typeName arrayName[value]; e.g: – int someArray[3]; Index starts from 0!!! –someArray[0] = 1; –someArray[2] = 2;

Initializations Rules for Arrays int array[4] = {2,6,4,5}; int secondArray[4]; secondArray[4] = {5,6,7,8}; // error!!! secondArray = array; //error!!! float Hotel[5] = {1.1, 2.2}; long total[500] = {0};

short array[] = {1,2,3,4};

String Series of characters stored in a consecutive bytes Create a string as an array but the last element must be the null character ‘\0’ – e.g char dog[5] = {‘b’,’e’,’a’,’u’,’x’}; //NOT!! char dog[6] = {‘b’,’e’,’a’,’u’,’x’,’\0’}; // STRING!!

More examples char dog[5] = “beaux”; //a better way null character is implicitly included. char name[]=“c++”; // compiler counts char boss[8]=“Arvind”;

#include int main() { int arSize = 20; char name[arSize]; char dessert[arSize]; cout << “Enter your name: “ << endl; cin >> name; cout << “Enter your dessert: “ << endl; cin >> dessert; cout << name << “ has selected: “ << dessert << endl; return 0; }

Another way to read a string #include int main() { int arSize = 20; char name[arSize]; char dessert[arSize]; cout << “Enter your name: “ << endl; cin.getline(name, arSize); // reads through newline cout << “Enter your dessert: “ << endl; cin.getline(dessert, arSize); cout << name << “ has selected: “ << dessert << endl; return 0; }

The String class To define strings more easily: –Include the string class: #include string str_1 = “jaguar”;

Assignment & Concatenation & Appending char char_1[20]; char char_2[20] = “jaguar”; string str_1; string str_2 = “panther”; char_1 = char_2; // INVALID!! str_1 = str_2; // VALID!!

Appending string str_3; str_3 = str_1 + str_2; // join str_1 and str_2 str_1 += str_2; // add str_2 to the end of str_1

More string operations: Copying: #include – strcpy(char_1, char_2); //copy char_2 into char_1 strcat(char_1, char_2); //append char_2 to char_1 Size of a string: – char charOne[20] = {‘p’,’i’,’e’}; – string strOne = “pie”; – strlen(charOne); –strOne.size();

Increment & Decrement Increment: ++ int a = 20; int b = 20; cout << “a: “ << a << “ b: “ << b << endl; cout << “a++: “ << a++ << “ ++b: “ << ++b << endl; cout << “a: “ << a << “ b: “ << b << endl;

a: 20 b:20 a++: 20 ++b:21 a:21 b:21 int x = 5; int y = ++x;

Decrement: -- Same rules as increment ( i.e. ++)

Loops different types: – for – while – etc.

For Loop for(initialValue; test-expression ; update- expression) { BODY }

Example #include int main() { int a; for (a = 0; a < 10; a++ ) { cout << a << endl; } return 0; }

While loop while(test-expression) { BODY }

Example #include int main() { int arSize = 20; char name[arSize]; cin >> name; int a = 0; while (name[a] != ‘\0’) { cout << name[a] << endl; a++; } return 0; }

Conditional Statements if statements Syntax: if (condition) { IF_BODY } else { ELSE_BODY }

Conditions: Relational Expressions: –Comparisons: e.g »== tests equality »> is greater?

Example int number; cin >> number; if ( number < 0) { cout << “Negative Value” << endl; } else { cout << “Non-negative Value” << endl; }

Comparing two strings #include int main() { int arSize = 20; char name1[arSize]; char name2[arSize]; cout<<“String1”<<endl; cin>>name1; cout<<“String2”<<endl; cin>>name2;

int len1,len2,a; len1=strlen(name1); len2=strlen(name2); bool flag=true; if (len1 != len2 ) cout<<“different”; else { for (a=0; name1[a]==name2;a++); if (a==len1) cout<<“The same”; else cout<<“different”; }

Sort an Array of Integer #include int main() { int arSize = 20; int ArrayNumber[arSize]; int indx; for(index=0; index <20; index++) { cout<<“enter an integer”<<endl; cin>>ArrayNumber[index]; }

int i,j; int temp; for( i=1; i< 20;i++) for (j=0; j< i;j++) if (ArrayNumber[ j] > ArrayNumber[ j+1]) { temp= ArrayNumber[ j ]; ArrayNumber[ j ]=ArrayNumber[ j+1]; ArrayNumber[ j+1]=temp; }