Introduction to C++

© 2000 Krishna Myneni

``Programming is the activity of communicating algorithms to computers.'' Kelly & Pohl.

C++ Keywords

The following keywords are part of the standard C++ language. They should not be used as identifiers for variables or functions. Keywords particular to C++ are shown in boldface.

asm auto break case catch
char class const continue default
delete do double else enum
extern float for friend goto
if inline int long new
operator private protected public register
return short signed sizeof static
struct switch template this throw
try union unsigned virtual void
volatile while      

Program Organization in C++

In a procedural language a program consists of static data and a collection of functions.

// Global data

int checking_balance, credit_balance, credit_limit;

// main procedure (function)

void main ()
    checking_balance = 1000;
    credit_balance = 500;
    credit_limit = 2000;
    int cost = 500;

    purchase (cost);

void purchase (int cost)
    if (cost < checking_balance)
      pay_by_cash (cost);
      pay_by_credit (cost);

void pay_by_cash (int cost)
    checking_balance -= cost;
    if (checking_balance == 0) cout << "You're broke!";
    if (checking_balance < 0) 
      transfer_from_savings (abs(checking_balance));

void pay_by_credit (int cost)
    if (credit_balance + cost > credit_limit)
      cout << "You've exceeded your credit limit!";
      credit_balance += cost;

C++ supports procedural programming. It also allows another more powerful form of organization known as object oriented programming.

// Classes
class CreditCard {
    int balance;
    int limit;
    void purchase (int cost);

class CheckingAccount {
    int balance;
    void purchase (int cost);

class Consumer {
    CreditCard plastic;
    CheckingAccount checking;
    Cosumer (int starting_balance, int credit_limit);
    void purchase (int cost);
    void pay_by_cash (int cost);
    void pay_by_credit (int cost);

void main ()
    Consumer Tom(100, 1000), Andrea(250, 5000);

    Tom.purchase (500);
    Andrea.purchase (120);

Each class is designed to represent a single concept. An instance of a class is called an object.

Intrinsic Types

Basic data types provided by C++ are

char character
int integer
long long integer
float single precision floating point
double double precision floating point

The char, int, and long types may be signed or unsigned. The intrinsic types may be mixed in assignment expressions, e.g.

     int i = 10;
     unsigned long l;

     l = i;

The sizeof() operator may be used to determine the size in bytes of any type.


C++, like C, provides a rich set of operators which fall under the general categories

The relational operators are

 ==     equal to 
 !=     not equal to
 <      less than
 >      greater than
 <=     less than or equal to
 >=     greater than or equal to

The arithmetic operators are

 +       add 
 -       subtract
 *       multiply
 /       divide
 %       remainder
 ++      increment
 --      decrement

The bitwise operators are

 &       bitwise AND
 |       bitwise OR
 ~       bitwise complement
 ^       bitwise XOR
 <<      bitwise left shift
 >>      bitwise right shift

The logic operators are

 &&      AND
 ||      OR
 !       NOT

The assignment operators are

 =       assignment
 +=      arithmetic assignment
 <<=     bitwise assignment 

Flow Control Structures

C++ provides flow control structures for branching and looping like other structured languages. These are

if () {} else {}
if () {} else if () {} ... else {}
switch () { case 0: {} case 1: {} ... default: {}}
while () {}
do {} while ()

The break and continue statements also control branching within loops.


Functions in the C Standard Math Library

Be sure to include the math header file in any program that uses the math library functions.

#include <math.h>

Most of the functions take a double value as their argument, and return a double value. They would be declared as

double func (double x);

Name Description
acos Return arc cosine of $x$
asin Return arc sine of $x$
atan Return arc tangent of $x$
atan2 Requires arc tangent of $x/y$
atof Convert string to floating point number
ceil find smallest integer not less than $x$
cos Return cosine of $x$ (radians)
cosh Return hyperbolic cosine of $x$
exp Return $e^x$
fabs Return absolute value of $x$
floor Return largest integer not greater than $x$
fmod Return remainder of $x/y$
frexp Split argument into mantissa and exponent
ldexp Return value given mantissa and exponent
log Return natural logarithm of $x$
log10 Return base 10 log of $x$
modf Break a number into whole and fractional parts
pow Return $x^y$
sin Return sine of $x$ (radians)
sinh Return hyperbolic sine of $x$
sqrt Return positive square root of $x$
tan Return tangent of $x$ (radians)
tanh Return hyperbolic tangent of $x$