ch2part1

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Chapter 2:

C++ FUNDAMENTALS(Part 1)

DCS5088 :: Chapter 2 (part 1) 2

Objectives

• Know the differences between C and C++

• Write simple C++ programs• Know how to use the cin and cout object• Implement selection structures


2.1 #include<iostream> • This is a pre-processor directive for C++• Contains definitions for functions or classes• Any other header files?

Yes. Example: cmath, iomanip• Notice that the header file no longer needs to

end with a ‘dot h’


2.2 using namespace std• Specified after including the iostream• Std = standard• A namespace is a collection of prewritten

classes and functions or names, such as cout and cin.

• The names you use in the program will have the meaning defined for them in the std namespace.


2.3 cout and cin

• cout standard output stream for displaying output to screen uses the stream insertion operator, <<

• cin standard input stream get user inputuses the stream extraction operator, >>


2.4 A simple C++ program#include<iostream>using namespace std;int main(){ int num; cout<<"Enter a number : "; cin>>num; cout<<"The number is …"<<endl; cout<<num<<"\n"; return 0;}


Output:


2.5 Create new line

• Use endl • Use \n (string constant)


2.5 Create new line

#include<iostream>using namespace std;int main(){ cout<<"hello …"<<endl; cout<<"\nMy name is Ali\n"; cout<<"I’m 21 years old";

}


2.6 Variables and Assignments

• C++ has rules you must follow in dealing with variables.

• For instance, you must declare all your variable names in your programs, which means to list your variables and indicate what type they are.


Example#include<iostream>using namespace std;int main(){ int student_id; float cgpa;

student_id=10401222; cgpa=3.96 ; cout<<student_id<<" "<<cgpa<<endl; student_id=10401223; cgpa=3.67 ; cout<<student_id<<" "<<cgpa<<endl; return 0;}


2.7 More on Variables

• Variables are implemented as memory locations.

• The compiler assigns memory location to each variable name in the program.

• The variable name is actually a label to memory locations allocated during the creation of the variable


Example

int student_id; float cgpa;

74 75 76 77 78 79 7A

0012FF74 4 bytes 4 bytes0012FF78

7B 7C

Type: float intName: cgpa student_id


Example

student_id=10401223; cgpa=3.67 ;

74 75 76 77 78 79 7A

0012FF74 4 bytes 4 bytes0012FF78

7B 7C

Type: float intName: cgpa student_id

3.67 10401223


2.8 Selection Statements

• if/else: general method for selecting an action for conditional execution, linearly checks conditions and chooses first one that evaluates to TRUE.

• switch: a potentially more efficient method of selecting actions, since it can use a “jump table."


2.8.1 If control structure- basics• Simple if statements if (expression) statement;

• Block if statements if (expression) { executable statement 1 executable statement 2 . . . }


2.8.2 Simple if-elseif (expression){executable statement 1aexecutable statement 1b. . .}else{executable statement 2aexecutable statement 2b. . .}


2.8.3 Nested if-elseif (outer){

if (inner){. . .}else{. . .}

}

else{. . .}


Example#include<iostream>using namespace std;int main(){ int num;

cout<<“Enter a number : “; cin>>num;

if (num < 10) { if (num > 5)

cout<<“\nThe number is between 5 – 10”; else cout<<“\nThe number is less than 10 }


Example (cont…)else cout<<“\nThe number is greater than 10”;

} //end of main()


2.8.4 If-else-if and switch• Provide similar capabilities• When one block is executed, the others

are bypassed


Example (using if-else-if)#include<iostream>using namespace std;int main(){ char input;

cout<<"Enter either A, B or C: "; cin>>input;

if (input == 'A') { cout<<"\nYou’ve entered A"; }

Continue…


Example (using if-else-if) –(cont…)

else if (input == 'B') { cout<<"\nYou’ve entered B"; } else if (input == 'C') { cout<<"\nYou’ve entered C"; } else cout<<"\nInvalid input"; return 0;} // end of main()


Example (using switch)#include<iostream>using namespace std;int main(){ char input;

cout<<"Enter either A, B or C: "; cin>>input;

switch(input) { case 'A' : cout<<"\nYou’ve entered A";

break;


case 'B' : cout<<"\nYou’ve entered B"; break; case 'C' : cout<<"\nYou’ve entered C"; break;

default : cout<<"\nInvalid input"; } //end of switch return 0;} // end of main()

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