Arduino club

1. Arduino club Session 1: C & An Introduction to Linux

2. The Big Black Box cd – "Change Directory“ ls – “List Directory Contents” mkdir – "Make Directory" nano – Terminal Text Editor gedit – GUI Text Editor (boring people only) gcc – For compiling your code

3. Using GCC GCC is the ‘GNU Compiler Collection’, and is how we compile our code: • gcc <input file> -o <output file> • All C files must end with .c • The output file doesn’t need an extension • You run it with ./<output file>

4. Basic Program Outline • Pre-processor Commands • Function definitions • Global Variables • Functions

5. Annoying Syntax As with all language, there are some things you must always remember: • End most lines with a ‘;’ • Start subroutines with a ‘{‘ and end with a ‘}’ • Indent with either tabs or spaces, but not both • All variables must have their type declared

6. Hello World /* Hello World program */ #include<stdio.h> void main(){ printf("Hello World \n"); } This line is a comment, it doesn't run with the program This tells the program to include the "stdio" library, for input & output functions Starts the "main" function Prints "hello world", followed by a new line, to the terminal

7. Storing values

8. Variables & Constants Defining Variables: • Define its type • Name it: • No spaces • Use camelCase or underscores_like_this, just be consistent • Assign its value e.g. "intmyNumber = 4;" e.g. "char my_char = D;" For Constants, simply prefix the statement with "const" e.g. "constintconstantNumber = 42;"

9. Data Types • INT • Integer, used for storing whole numbers • E.g. 5 • LONG • Like an integer, used for storing bigger numbers • E.g. anything above 32767 or below -32768 • FLOAT • Used for storing decimals • E.g. 3.14159265 • CHAR • Used for storing letters (can also store numbers because fuck you that"s why) • E.g. Y

10. Arrays Arrays are groups of data of the same data type You define them with a type, name and length: e.g. int scores[7] = {1,1,2,3,5,8,13}; e.g. char myLetters[9] = {“d”,"a","n","s","m","e","l","l","s"}; You can address specific items in the array by calling them as arrayName[position], e.g. - scores[2] would be 2 - myLetters[4] would be "m" n.b. computers count from 0, so -1 from what you think the position is

11. Strings • Strings are stored as arrays of characters, however we can define them easily with: • char *myString = “I Love Strings!” • We can also create arrays of strings: • char *stringArray[4] = {“I”,”Love”,”Strings”,”So”,”Much”} • This means that the array • char myLetters[9] = {“d”,"a","n","s","m","e","l","l","s"} • Could also be written as: • char *myLetters=“dansmells”

12. Scope Scope is the name for where a variable is accessible from • A variable with ‘Global’ scope can be accessed from wherever • A variable with ‘Local’ scope can only be accessed from within its function #include<stdio.h> int x = 4; long function(int x){ printf("%d \n",x); } void main(){ function(5); printf("%d \n",x); }

13. Basic maths

14. Addition, Subtraction, Multiplication, Division, Modulus & Powers • Addition is done with "+" • This works with characters too, but produces some funky outputs: • e.g. "d + f = Ê" • Subtraction with "-" • Same as with addition, works with every data type • Multiplication with "*" • When using floats, make sure that your result is also a float data type, otherwise it will give an incorrect answer • Division with "/" • Same as multiplication, make sure your datatypes are correct • Modulus with "%" • Finds the remainder when two numbers are divided

15. Compound Operators We can use these to make mathematical operations on variables easier to read: • x = x + 3 • x += 3 • x = x - 3 • x -= 3 • x = x * 3 • x *= 3 Etc…

16. Input & output

17. scanf() & printf() "scanf()" is used for taking input from the terminal: • scanf(“%c”,&myChar); • This will wait until the user inputs a character, and will then store it in "myChar" • Variables must all be declared first "printf()" is used for outputting to the terminal: • printf(“Hello World”); • This will output "Hello World" to the terminal • printf(“"myNumber is %d”,myNumber); • This will output the contents of myNumber to the terminal

18. Formatting Input & Output When inputting & outputting variables, we have to format them correctly:   %c for characters, %d for integers, %f for floats

19. Conditionals

20. "If" Statements These allow us to perform an action, if a condition is met, and otherwise perform another action #include<stdio.h> inti; void main(){ printf("Enter a number! \n"); scanf("%d",&i); if (i == 0){ printf("that number was zero \n"); } else { printf("that number was not zero \n"); } }

21. Logic Operators • == means equal to • != means not equal to • && means AND • || means OR • > means greater than • < means less than • >= means greater than or equal to • <= means less than or equal to

22. Loops

23. "While" Loops These allow us to loop code indefinitely until a condition is met: #include<stdio.h> //You get the point int x = 0; //Declares x variable void main(){ //Starts main while(x<100){ //Starts while loop with condition x++; //Increases x by one printf("%d \n",x); //Prints value of x } }

24. "For" Loops • Used for performing actions a set amount of times • Also useful for looping through an ARRAY • Started by: "for (initialization, condition, increment) {(functions in here)}" • Initialization is run only once, and is usually decleration of the condition variable • Condition decides when the for loop will stop, once it is false the loop will be exited • The increment decides how the condition variable will be increased/decreased #include<stdio.h> /* includes stdio library, necessary */ void main(){ // starts main function for (int x = 0; x<100; x++){ // sets how the for loop will run printf("%d \n", x); /* prints "x" until it"s equal to 100, then stops */ } }

25. "For" Loops with Arrays We can also iterate through an array with a for loop, as shown below: #include<stdio.h> //Necessary int myNum[2]={1,3}; //Defines array int arraySize=sizeof(myNum)/sizeof(int); //Works out length of the array int i=0; //Defines i for iterating void main(){ //Starts main for(i=0;i<arraySize;i++){ //Starts for loop printf("%d \n",myNum[i]); //Outputs each field } }

26. A Note about Iterating • Iterators usually take the form of: • Variable++ • This will increase "Variable" by one every iteration • Variable-- • This will decrease "Variable" by one every iteration • We aren’t limited to this, an iterator can have any mathematic function applied to it, however these are the most common

27. Functions

28. Why use functions? • Less repeated code • Easier to fix bad code • Neater

29. Defining Functions Defining a function is very easy, it goes like so: return_type function_name(arguments,with,datatypes){ /* code goes here*/ } Just remember to define them before you call them!

30. Calling Functions Calling a function is even easier: function_name(arguments);

31. Variables can be functions too! If we do x = functionName(arguments) x will then hold the return value of the function ‘functionName’