Lesson3

 

Data types in C++

 

Integer - positive or negative whole number including zero. (keyword int)

 

Largest and smallest integer available dependent on the compiler/computer. 

2 bytes - 32,767   to  -32768

4 bytes - 2,147,483,647 to +2,147,483,648

 

ex. 5    -32     24   0

 

Floating - Point Numbers - signed or unsigned real numbers having a decimal point.

 

ex. 5.0    4.      -2.33333   

 

float - 4 bytes

double 8 bytes

 

Sometimes displayed in exponential notation.

 

Number   Exponential Notation    Scientific Notation

23.5                        2.35e1                 2.35 X 101

0.235                   2.35e-1                         2.35 X 10-1

 

Moving the decimal point right gives a positive exponent.

Moving the decimal point left gives a negative exponent.

 

Character - 1 byte

letters, digits, all special characters on the keyboard such as .  ,  !  ? @ # $ % ^ & * ( ), etc. 

 To display a single character, we enclose it in single quotes.

 

cout << 'a' ; //displays the letter a 1 byte long

 

cout << "a"; // not a character but a character string (2 bytes)

 

cout << “The rain in Spain”; //character string of 17 characters.

 

 

Variable - a name used to denote a section of computer memory.  Each cell in memory has an address.  The variable name is used instead of the actual numeric address. 

 

We use declaration statements to tell the computer to put aside space in memory and associate that space with a variable.  The amount of space set aside depends on the data type of the variable.

 

General form of a declaration statement:

 

datatype  variableName;

 

Ex.

int num1;  //integer variable

int num2;

float average;   //float variable

char letter;       //character variable

 

multiple declarations can be written as follows:

 

int num1, num2;

 

Variables get values placed into their memory locations using assignment statements.

 

num1 = 5;

letter = 'a';

 

The equal sign does not denote equality in the arithmetic sense.  What appears on the right hand side of the equal sign is evaluated and then stored in the variable location on the left.

 

Variables of type string need the string library to be included in the program.  In the first versions of C++ string variables and the functions used with them were not a part of the language. 

 

#include <iostream>

#include <string>

using namespace std;

 

int

main()

{

     int num1, num2;

     float amount;

     char letter;

     string name;

 

     num1 = 4;

     num2 = 9;

     letter = 'z';

     amount = 22.50;

     name = “Imberman”;

     cout << num1 << ' ' << num2 << ' ' << letter

          << ' ' << amount << endl;

 

     num2 = 15;

 

     cout << num1 << ' ' << num2 << ' ' << letter

          << ' ' << amount << endl;

 

     cout << name << “ is an interesting Profesor.” << endl;

     return 0;

 

}

 

We can initialize a variables value in the declaration statement.

 

#include <iostream>

#include <string>

using namespace std;

 

int

main()

{

     int num1, num2;

     float amount;

     char letter;

     string name;

 

     num1 = 4;

     num2 = 9;

     letter = 'z';

     amount = 22.50;

     name = "Imberman";

     cout << num1 << ' ' << num2 << ' ' << letter

          << ' ' << amount << endl;

 

     num2 = 15;

 

     cout << num1 << ' ' << num2 << ' ' << letter

          << ' ' << amount << endl;

 

     cout << name << " is an interesting Profesor." << endl;

     return 0;

 

}

 

Notice: Proper format - place declarations after the opening curly bracket.  Skip a line after the declarations. 

 

The variable name is a tag for the first byte of the memory location that will store the given information.

 

In reality, this corresponds to a memory address.  We can print out the address of a variable by placing an ampersand (&) in front of the variable's name in a cout statement.

 

Ex.  cout << num1 << '  ' << & num1;

 

The above prints out the value of num1 and its address.

 

#include <iostream>

using namespace std;

 

int main()

{

  int num;

 

  num = 22;

  cout << "The value stored in num is " << num << endl;

  cout << "The address of num = " << &num << endl;

 

  return 0;

}

 

OUTPUT

The value stored in num is 22

The address of num = 006AFDF4

Press any key to continue

 

 

Simple arithmetic expressions:

 

+ addition

- subtraction

* multiplication

/ division

 

sum = 4 + 5;

num2 = 6;

num3 = 8;

sum = num2 + num3;

 

Any expression can appear on the right hand side of an assignment statement.  An expression is any combination of constants, variables, and function calls that yield a result. 

 

Only a single variable is allowed on the left hand side of an assignment statement .