Intro to Programming

RoboRebels Intro to Programming

Topics • Hardware and Machine Code • The Building Blocks of Programs • Program Design • Object Oriented Programming • Our Robot

Hardware • The two most important hardware components to a programmer are: • The CPU • RAM

The CPU • The Central Processing Unit is the ‘brain’ of a computer. It is responsible for executing programs. • While a program is running, it uses a processor Thread.

RAM • Random Access Memory gives a computer a place to store information quickly and temporarily. • Programs are stored in RAM they are running, and can use it to store information. • RAM is not long term storage.

What is a Program? • A program is a list of instructions to tell a computer what to do. • The most basic form of computer instructions is called machine code. Machine code is very difficult for a human to read and understand. • For example: add eax, VariableX adds two numbers together • Programming in machine language is tedious and error prone. Programming today is usually done in a variety of high level programming languages

High-Level Programming Languages • Most programs today are written in high-level programming languages, such as Java or C++ • Since these high-level programs’ purpose is to allow the programmer to understand and write programs more quickly, they cannot be understood directly by a computer. • In order to be executed, high-level code needs to be compiled into machine code. A compiler performs this translation.

Java • Java code is compiled into bytecode, which can be interpreted and run by the JVM, or Java Virtual Machine, which allows programs written in Java to be completely platform-independent.

The Building Blocks of Programs • Data and Instructions are the two basic components of a program.

Data • Programs store data in variables. These variables are memory locations that can be accessed and modified. • Since a variable might need to represent several different types of information, several can be used: • Boolean (true/false) • Integers ( 42, 0 -1) • Floating Point (3.14, 0.0, -2.1) • Characters (‘h’, ‘z’ ‘5’, ‘<‘) • Strings (A group of characters): “Hello Programming”

Variables • In computer programs data lives in memory • In order to access this data you must know specific location of the data (this is called an address) • It’s much easier to use a variable, which is named by you, than a computer memory address • Example:int Length = 24; float PI = 3.14; char MiddleInitial = ‘M’; string FirstName = “Derek”;

Instructions • A program runs a sequence of instructions from the top down. • Control Structures are instructions that alter how the program executes certain commands. • Arithmetic instructions • Add, subtract, multiply and divide (+, -, *, /)

Instruction Examples • int Area = 0, Length = 2, Width = 5; Area = Length * Width;Advanced users: Look up “Order of Operations in Programming”http://en.wikipedia.org/wiki/Order_of_operations#Programming_languages

Control Structures • All control structures affect program flow • Branches – test a condition to decide between two or more courses of action. • Conditions evaluate either true or false • for example, a condition that tests if 5 is equal to 5 would evaluate to true. • Loops – repeat a group of instructions. • Subroutines (Functions) – Allow you to “jump” to a group of instructions, perform them and then “jump” back to where you were.

Branches • Branches help us when we need to perform a group of instructions in one situation and another group of instructions in different situation • Example:If my gas tank is almost empty Then fill it up with gasOtherwise Keep driving • Example 2:If my car is red Then touch up with red paintIf my car is black Then touch up with black paint

Loops • Loops perform a group of instructions repeatedly and will only stop when certain condition is met. • This helps with programming because you do not need to repeatedly write out instructions over and over. • Also, what if you don’t know when the loop should end when you are writing the program? • Example: For as long as I own my current car do the following Fill gas tank when it is near empty Change oil every 4000 miles Perform other maintenance when needed

Nesting Loops and Branches • Our programs would be very limited if we couldn’t combine loops and branches with other loops and/or branches • Example:For each year that I have my car For every four months Get your wheels aligned

Subroutines • When programs get larger and more complex it gets harder and harder manage code • One way to manage this complexity is to break the program down into “chunks”, these are called Subroutines, Functions or Methods • Subroutines allow you to reuse functionality in your programs

Subroutine Example

Code Reuse • Why would we want to create subroutines to foster the reuse of code? Programmers are LAZY!

Code Reuse • Saves time • Less potential for error • Easier to find errors and test • Using subroutines or the idea of breaking code into chunks helps to simplify the process of programming a robot.

Design • Software can become very complicated. Design is very important to the creation of a successful program. • Programmers must analyze the problem to be solved and design a program to solve it. Several concepts and tools become very useful in this process. • Top-down and bottom-up • Encapsulation • Object Oriented Programming

Top-Down and Bottom-Up • A top-down approach to solving a problem starts with a general solution and breaks it down into small, easily solvable parts. • The bottom-up approach begins with solving the easiest problems, and works up to the complete solution. • In reality, a combination of these approaches is utilized.

Encapsulation • Encapsulation refers to the reusability of a piece of a program. Ideally, a component should be “modular”. Modules interact with the rest of the program in a simple and straightforward manner. • How an encapsulated module works is not important to the whole program, as long as it works correctly. This is called information hiding.

Object Oriented Programming • Object Oriented Programming, or OOP, focuses on encapsulation. • An object acts as a module that contains its own data and subroutines. • OOP begins with identifying the objects involved in the problem. • An OOP program uses a collection of objects that can interact with each other. • Object oriented programming is a very effective tool used in the structure and design of a program.

Objects • Why use the concept of objects? • Easily model real-world objects • Reusable blocks of code and data • Easily test out concepts • Create complex concepts with object relationships • Object Data (Members) • Think of it as adjectives for objects • Example: Color, temperature, position • Object Actions (Methods) • Think of it as verbs for objects • Example: Move, kick, extend

“has-a” Relationship • Not only can objects have Members and Methods, but they can contain other objects • The “has-a” relationship is defined as an object containing another object • Example: • We have a Robot object • This Robot object has 4 motor objects

“is-a” Relationship • In OOP there is a concept called inheritance. This is where you can derive a new object from another object • This is best shown with an example • Example: • We have an object called SpeedController • Our robot uses two different types of speed controllers • Victor • Jaguar • So, we can create two new objects from the SpeedController object which contains the functionality of a SpeedController, but has special Members and/or Methods which are only necessary for a Victor or a Jaguar

The Robot and OOP • Think of a robot just as you would a human. You can divide a human into 3 distinct parts:

Our Robot • The robot that this club creates will need to perform certain tasks. The very basic requirements of the robot are: • Controlling actuators and motors • Receiving input data from sensors • Mapping the robot’s actions to joystick controls • Knowing what to do on its own (autonomous mode)

Intro to Programming