Chapter 2: Numerical Data Types¶

Data types¶

what they are the data types used to represent numbers

variables¶

what they are declaring and defining them

Background¶

represent different types of calues depending on task. C++ able to represent numerical and character values using specific data types.

Definition¶

Values in programming have a specific data type that determins size it takes in memory and type of value that is stored.

Numerical Data Types¶

integer values¶

Variables¶

Background¶

Definition¶

Variable syntax¶

datatype variableName;

declares a single varibale with no initial value ie: int x1; (makes variable called "x1")

datatype variableName, variableName, variableName...;

declares multiple variables of the same datatype, all with no initial values seperate each variable name with a comma ie: int x,y,z (makes variables called "x", "y", "z")

datatype variableName = initial value;

defines a signel variable with an initial calue

datatype variableName = initial value, variableName = initialcalue...;

defines multiple variables of the same datatpye each with its own initial value

notes: you can declare/define as many variables as you want in a single statement, but they all must be the same data type the "=" character used above is the assignment operator - format is: variable = value; where it will assign the variable on the left the value on the right

Rules¶

• variable names must start with a letter or an underscore but can contain a mix of uppercase and lower cases , numbers, and underscore

• cannot be any C++ keyword (int, float, double, main, class, case, etc...)

• variable names are case sensitive so the variables int pennies; and int Pennies; are two different variables make cariable names something significant. it should be clear what it represents

Integer Values¶

• keyword: int

• when to use int use int to represent data that can only be identified in whole numbers

• can perform arithmetic with integers (+, -, *, /, %)

  modulus operator: %¶

  op1 % op2 results in the remainder of dividing op1 by op2
      ex:
      `int x=30, y=6, z=7`
      `int v=x%y; //v=0`
      `int w=x%z; //w=2`
  

a op= b → a = a op b can be used with -=, *=, /=, %=

variableName = value; this value can be any expression that is the same datatype as the variable

increment and decrement operators ++ increment by 1 -- decrement by 1 - pre-increment/pre decrement (++x,--x): - increment/decrement x by 1 and THEN access value - post increment/post decrement (x++, x--) access the calue of x, and THEN increment/decrement by

Floating point values¶

C++ keyword: double when to use double use double when the value contain decimal points.

similar to integers, we can use arithmetic operators on these types.

note: cannot use % with floating point values. can use fmod(), part of the cmath library

Constants¶

a constant is a named value that cannot be changed. Use constants in your program when you are representing a fixed value

Syntax¶

const datatype NAME = value;

Example Program¶

Write a C++ program that asks the user the number of pennies, nickles, dimes, and quarters they have, then display their total to them.

Steps to take¶

1) initialize variables 2) prompt the user for the number of each coin 3) calculate total of each coin 4) calculate total of all coins 5) display the total

What we need for each step¶

1) Declare variables for each coin 2) cout to ask for the coins, cin to take user input 3) do some sort of arithmetic to calculate total of the coins 4) do some more arithmetic 5) cout to display the total

#include <iostream>
#include <iomanip>

using namespace std;
int main()
{
    //init variables for each coin
    int numPennies = 0, numNickels = 0, numDimes = 0, numQuarters = 0;

    //prompt user for each coin
    //ask the user to enter the amount for each
    cout << "Please enter the number of pennies you have: ";
    cin >> numPennies;
    cout << "Please enter the number of nickels you have: ";
    cin >> numNickels;
    cout << "Please enter the number of dimes you have: ";
    cin >> numDimes;
    cout << "Please enter the number of quarters you have: ";
    cin >> numQuarters;

    //calculate the total for coins
    double total = (numPennies*.01)+(numNickels*.05)+(numDimes*.1)+(numQuarters*.25);

    //display the total to the user
    cout << fixed << setprecision(2) << "Your total is: $" << total << "\n";
}

Using pre-definied C++ Libraries¶

C++ librarys¹¶

• your main function (int main()) is what controls the c++ program, but within main you can call other functions Definition of cunctions: a function is a group of statemtns that perform a specific task
• by including pre-defined libraries, we have access to the functions within them.
• syntax for using predefined functions: functionName (parameters)
• visit

cmath numerics library²¶

to use functions in cmath, have the following line in your program.

#include <cmath>

Things to remember¶

• you are limited to chars that are on your keyboard
  • no squareroot symbol
  • no log
  • no exponents (limited to ASCII char space)
• before you implement the statement in your program, make sure you have all the necessary variables/values
  • if your formula/expression uses specific variables, be sure that they have been decalred.
• include all necessary libraries

Lets try an example with the quadratic formula!

Quadratic formula example¶

\(\(X_{1,2} = \frac{-b\pm\sqrt{b^2-4ac}}{2a}\)\) - I have a, b, c

#include <iostream>
#include <cmath>

using namespace std;
int main()
{
    double a,b,c
    double x1 = (-b+sqrt(pow(b,2)-4*a*c))/(2*a);
    double x2 = (-b-sqrt(pow(b,2)-4*a*c))/(2*a);

}