Hello, robot

Your first program

C++ is compiled: when you press Run (or ⌘/Ctrl + Enter), a compiler first checks your whole program and turns it into machine code, and only then does it run. Here's a complete program:

#include <iostream>

int main() {
    std::cout << "Hello, robot!" << "\n";
}

• #include <iostream> brings in the part of the standard library that prints text.
• Every program starts at main. Its instructions go between the curly braces { } and run from top to bottom.
• std::cout is the console. << sends a value to it, and you can chain as many as you like. "\n" starts a new line.
• Each instruction ends with a semicolon ;. Forget one and the compiler stops with an error that names the line.

Text in double quotes is a string. Numbers don't need quotes.

Variables

A variable is a named value, and in C++ every variable has a type, written before its name:

int joints = 4;              // a whole number
double speed = 0.5;          // a number with a decimal point
std::string color = "red";   // text (needs #include <string>)

From then on, use the name wherever you'd use the value. You can store a new value later (speed = 0.8;), but the variable keeps its type: joints = 4.7; quietly stores 4, because an int has no room for decimals. Anything after // is a comment, which the compiler ignores.

std::cout doesn't add spaces between values, so put them in the text yourself:

std::cout << "The " << color << " ball" << "\n";   // The red ball

Your task

1. Give the robot arm a name: store a string in a std::string variable called name.
2. The arm has four joints. Store the number 4 in an int variable called joints.
3. Print a sentence like Rex has 4 joints, using both variables.