Week 1: Program Basics, Variable Declaration, Loops, Arithmatic Operators, and Comments

• Hello World Example: Use this simple example to ensure that you are able to compile and run programs with the development environment. To compile and run with DevC++:
  1. Download the program (right-click, save link target as...)
  2. Save to your computer - It is recommended that you make a new folder (directory) for each example.
  3. Open the file in DevC++.
  4. Go to the "Execute" menu. Click "Compile and Run".
• Area of Rectangles Example: This example computes and prints the area of rectangles that have widths of 10 and varying heights from 1 to 25. Compile, run, and read the output of the example. Look for the following main points:
  • Comments: A large comment at the top explains how comments work. Comments are critical to good programs and good teamwork!
  • Macro Definitions: The definition of RECTANGLE_WIDTH is a macro definition, used to contain a constant value and give it a symbolic name. Read the explanation of macros in the source code.
  • Main: The main function is the starting point for programs. The computer begins the program with the first line of main. With the robot, main begins as soon as the robot is powered on.
  • Variable declarations: See the comment in the source that explains declarations. A declaration sets aside memory for a variable and gives the variable a name. Remember... a variable has no value unless you assign one! If you forget to give a variable a value before using it, the compiler will not issue an error. Instead, your program will be unpredictable!
  • "for" loops: A loop is a convenient way to execute the same code multiple times. The body of the loop is executed until the "condition" of the loop is no longer true. The body of the loop is the part in braces - { ... } - following the for statement. If no braces are used, the body is just the next statement. A "for" statement has three main parts, all within parenthesis:
    1. Initialization (i = 1 in the example): This expression is executed only once, at the beginning of the loop. You typically use this to set up a counter variable (like "i" in the example).
    2. Test (i <= 25 in the example): Executed each iteration through the loop. If it evaluates "true", the body of the loop runs. If "false", the loop ends. Note that if this test is false when the loop initially begins, the body is skipped entirely.
    3. Increment (++i in the example): Executed at the end of each iteration of the loop, after the loop body executes but before the test condition. You typically use this to increment or add to a loop counter variable.
  • Assignment: You give variables a value with assignment (using the '=' operator). The example has two assignment statements: i = 0 and area = RECTANGLE_WIDTH * i.
  • Arithmetic: In the body of the loop, the example performs multiplication of the rectangle's dimensions. The '*' operator multiplies two values. Other operations available are addition (+), subtraction (-), and division (/).
  • Comparison: You can compare variables with statements like i <= 25. The <= operator checks if the first value is less-than or equal-to the second value. Most other mathematical comparisons are available, just as you'd expect.
• Additional Lessons:
  • While loops: A "while" loop is an alternative to a "for" loop. It looks like the following:

          while (test) {
             body
          }
          

    
    At the beginning of the loop, the "test" condition is executed. If it is true, the body executes once. The test is then executed again - if true, the body executes again. This continues until the test is false.
• Perimeter Exercise: Take the area example and modify it to compute the perimeter of the same rectangles as the original. Also substitute a "while" loop for the "for" loop.

Week 2: Functions and Arrays

• Function and Array Example: This example illustrates the use of arrays and functions. Main Points:
  1. A function can be used to encapsulate a task in a program. It takes input in the form of arguments and can return a single value. Functions are a good way to contain code that might be executed multiple time or from multiple places in a program.
  2. The main function is a special function - the program begins there.
  3. Function prototypes state the existence of the function. They must appear in the file somewhere before they are used. They are typically done at the top of a file, or in a header file (we'll cover header files in another week). Note the prototype for the distance function.
  4. Function definitions contain the source code for what the function actually will do. A function definition can occur anywhere.
  5. Arrays contain a series of the same type of values in a big "chunk" of memory. They allow you to hold a set of values and make it easy to perform the same operation on multiple values. Note how the arrays of points can be iterated over in a loop. In this way, the loop can easily perform the same operations on a set of input data (in this case, the distance function is called, followed by a print statement). Each item in an array is called an element of the array.
  6. Arrays are declared in a similar way to simple variables (note the similarity between the declarations of "int i" and "int end_points[NUM_POINTS]")
  7. Arrays can be declared without values (see the declaration of end_points). In this case, you must give the size. The array is just a chunk of memory at this point, just like "int i" is an empty chunk of memory. We can't meaningfully use the array until it is given values. In this example, we give it values in the first "for" loop.
  8. Arrays can also be declared with initial values. See the declaration of start_points. An immediate assignment (=) gives the array initial values (in {braces}). Note that you don't need to give a size here - the size is determined from the number of values.
  9. "Indexing" an array is how we get the individual elements of the array. Arrays are "indexed" starting with an index of zero (0). The last element of an array has an index that is one less than its size (so the index of the last element of an array of 5 elements is 4!). Indexing is done by adding brackets to the end of the array name with the index in the middle (so, myarray[10] would give me the 11th element in an array named "myarray" -- remember, array indexes start at 0!). In the example program, the array is indexed with the loop variable, i. This lets us move one by one through the points arrays.
• Function and Array Exercise: The exercise program contains the skeleton of a full program. You are to add the missing parts. When complete, the program should compute and print out the perimeter and area of five rectangles. The 5 rectangles' dimensions are given in a comment above the main function.
  1. The exercise comes with two functions defined to print out the area and perimeter values once you have calculated them.
  2. Declare and define two new functions, one to compute area of a rectangle. One to compute perimeter.
  3. Create arrays to hold the dimensions of the rectangles.
  4. Use either a "for" or "while" loop to iterate over the elements of the arrays. Each iteration in the loop can represent one rectangle by indexing your arrays of the dimensions.
  5. The body of the loop should pass the dimensions of a rectangle to your new area and perimeter functions, then pass the results to the print functions.
  6. In the end, you should get 10 lines of print outs - one area line and one perimeter line for each of the 5 rectangles.

Week 3: If-Else and More Functions

• "If-Else": The if statement can be used to conditionally execute portions of your program:

    if (test) {
      /* This block is executed if test is true */
      ...
    } else {
      /* This block is executed if test is false */
      ...
    }
  

  
  The "test" section is just as in a "for" or "while" test. As the comments above explain, the first block is executed if the "test" is true. The second block is executed if the "test" is false. The "else" and following block are not necessary if you do not need them -- you can have just an "if" block. The example below shows an "if" statement that tests if a variable named "v" is greater than 100, and if it is, v is set equal to 100, otherwise 30 is added to v.
  
  Example "if" statement:
  

    if (v > 100) {
        v = 100;
    } else {
        v += 30;
    }
  

• If-Else Exercise: You are given an incomplete function that is supposed to compute the absolute value of any given integer value. You are to complete this function. When written correctly, your program should print a line for each test value in the main function along with the correct absolute value for the test value.

Week 4: Data types Until now, we've been using only integer data. These exercises introduce you to the other data types. Compile, run, and examine the results.

• Integer Types Example
• Data Types and Math Example
• Main Point: The different types have different sizes in memory and different ranges on which they can operate reliably. Keep this in mind when choosing types for your programs!

Week 5: Multiple files Until now, we've been compiling simple programs with only one .c file. Practical programs have many source files, even into the hundreds.

• Multiple files exercise: Download all 3 files to one folder on your computer. arm.c arm.h armtest.c
  To compile these in Dev C++, you will need to create a project and add the three files to the project. A "project" in Dev C++ and in most other programming software packages is a grouping of many source files together to form a single program when compiled.