Lesson 2: Data types

Now after gaining newfound knowledge on how to write a hello world app, let’s learn how to do computational arithmetic.

As you know from your basic algebra, variables can be assigned any name. However, in C++, the computer cannot solve equations. Variables can only be assigned values.

There are mainly 2 types of variables in C++: Strings and numbers. Classification is as follows:

String type:
Char (character)
string (an array of char)

Number type:
int
unsigned long (big int)
float (floating-point, i.e. decimal)
double (super precise floating-point number)
bool (Boolean, i.e. true and false)


To define a variable, we type in the code:

[var_type] [var_name];

And can be assigned values on instantiation:

[var_type] [var_name] = [var_value];

So for example, I can assign an int to hold value 3:

int abc = 3;

or Boolean xyz with false:

bool xyz = false;

You can assign multiple values:

int a = 3, b, c = 5;

to create a string hihi with value hello me:

string hihi = “hello me”;

Arithmetic:
C++ can do simple +, -, /, *, % (modulo)

A definition is as follows:

int a = 0;  //create a; assign a  = 0
a + 1;   //add 1 to a
a – 1;   //minus
a /1;   //divide
a*1;   //multiply
a%1;   //modulo
a++;   //a + 1 and store new value in a
a--;   //a – 1 and store new value in a
a += 2;   // add value 2 to a and store
a -= 2;   // subtract 2 from a and store
a /= 2;   //divide 2 from a and store
a *= 2;   //multiply 2 to a and store

That done, let us analyse a simple problem.

Evaluate the value of (9– 2) / ( (180.5 + 2) / 3):

A simple c++ program:

#include <iostream>
using namespace std;

int main() {
 int a,b,c;
 a = 9 - 2;
 b = 180.5 + 2;
 c = b / 3;
 cout << a / c << endl;
 return 0;
}

Of course, I can put the whole expression (9– 2) / ( (180.5 + 2) / 3) into C++, but this is to illustrate the picture better.

Hope you get a better picture of how to handle vars in C++, ciao!