Introduction to C++

Introduction to C++ Computer Science

Q: What is C++ • C++ is a compiled, object-oriented language • It is the “successor” to C, a procedural language • (the “++” is called the successor operator in C++) • C was derived from a language called B which was in turn derived from BCPL • C was developed in the 1970’s by Dennis Ritchie of AT&T Bell Labs • C++ was developed in the early 1980’s by Bjarne Stroustrup of AT&T Bell Labs. • Most of C is a subset of C++

People & Programs • User: an individual who runs, or executes, a program • Programmer: an individual who creates, or writes, a program

C++ Program Consists of… • Declarations • Define the use of various identifiers, thus creating the elements used by the program (computer) • Statements • Or executable statements, representing actions the computer will take on the user’s behalf

Identifiers • Names for various entities used in a program; used for... • Variables: values that can change frequently • Constants: values that never changes • Functions: programming units that represents complex operations • Parameters: values that change infrequently

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Compiler directive: Tells the compiler what to do before compiling • This one includes source code from another file

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Main function

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Header for main function • States… • data type for the return value • identifier for function • list of arguments between parenthesis(none for this function)

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Braces enclose the body of the function • They represent the start and end of the function

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Declarations and statements • Main body of function (or main part) • “//” represents the start of a comment

Simple C++ Program #include <iostream.h> int main() { // Declarations // Statements return 0; } • Return statement • specifies the value the function returns • All (almost) declarations and statements end with a semi-colon “;”

Simple C++ Program #include <iostream> int main() { // Declarations // Statements return 0; } • This program doesn’t do anything!

Sample C++ Program #include <iostream> int main() { int number; cout << “Enter a number” << endl; cin >> number; cout << “You entered: “ << number << endl; return 0; } • Variable declaration • The identifier number is declared as being of data type int, or integer

Sample C++ Program #include <iostream.h> int main() { int number; cout << “Enter a number” << endl; cin >> number; cout << “You entered: “ << number << endl; return 0; } • coutthe output statement for C++ • Note the direction of “<<“ • endl represents an end-of-line

Sample C++ Program #include <iostream.h> int main() { int number; cout << “Enter a number” << endl; cin >> number; cout << “You entered: “ << number << endl; return 0; } • cinthe input statement for C++ • Note the direction of “>>”

Sample C++ Program #include <iostream.h> int main() { int number; cout << “Enter a number” << endl; cin >> number; cout << “You entered: “ << number << endl; return 0; }

Assignment • Assignment is an operation that assigns the value of an expression to a variable • Ex. Total = 2 + 3 + 5 • First, the expresssion “2 + 3 + 5” is evaluated • Then, this value is assigned to the variable “Total”

Assignment • When a variable is declared, space is allocated in the computer’s memory for the variable • Each data type requires a different number of bytes in memory for storing a variable int - 2float - 4double - 8char, bool - 1

Assignment • When a variable is assigned a value, the value is placed into the variable’s memory location 10 Total = 2 + 3 + 5; Total

constants • Constants are expressions with a fixed value • Two types of constants • Declared Constants • Defined constants (#define)

Declared Constants • These are also called as typed constants • Syntax of declared constant is • const int numberOfAlphabets = 26; • const float PI = 3.14354;

Defined Constants • These constants are defined in the declaration part of the program • Syntax of defined constants is • #define numberOfAlphabets 26; • #define PI 3.14354;

Comments • Comments are used to document your code • Comments are not the part of your code • Its always a good practice to write comments • This class requires to the code to be well commented

Types of Comments • Two types of comments • Single line comments • Syntax: // • Example: //This is a single line comment • Block comments • Syntax: /* */ • Example: /* This is a Block Comment */

Introduction to C++