rs, Expressions, and the
If Statement

A
Gentle Introduction

Reference: Brooks, Chapter 2

Continuing from our last session, we now create a
new project
This time, we shall include it in the same workspace
as our existing project

 

Do a File|New and fill in the dialog as we did before
This time, however, I checked the Add to current workspace button
The default would be to make it a subfolder of hello

 

Now our workspace has two projects in it.  One
is the project from the previous cha</span><span class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt;">pter, hello.  The other is our new project,
circle.

Notice the hello.c file is still open

 

Select the File|New menu option and fill in the dialog
Notice that you can choose any name you wish for
the file, but it must end with a .c
Visual Studio determi</span><span class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt;">nes which compiler to invoke according to the file's
suffix
A .c file is a C source file.  Visual Studio will
invoke the C compiler on it.
A .cpp file is a C++ source file.  Visual Studio will
invoke the C++ compiler on it.

 

As a result of this, you sho</span><span class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt;">uld see something like what we show below.
An empty window for main.c will appear superimposed
on top of the existing windows

Also, the circle project now has a + to the left
of it which we can click

 

Here we have a program to compute the area of a circl</span><span
class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt;">e

It asks the user to give the radius, performs the
computation, the prints out a result

 

Here again is the program
[Instructor: discuss the components
of this program to introduce next section]

/*

* File  : main.c

* Author: Robert C. Carden IV

*/

#include <stdio.h>

int main (void)

{

const double pi = 3.14159;

double radius, area;

printf ("Enter the radius of the circle: ");

scanf ("%lf", &radius);

/* area = PI times R^2 */

area = pi * radius * radius;

printf ("Using PI=%g to compute the area...\n", pi);

printf ("The area of a circle of radius %f is
%-10.4f\n",

             
radius, area);

return 0;

}

Here is an example run of this program:

 

Dissection
of the Circle Program - Comments

/*

* File  : main.c

* Author: Robert C. Carden IV

*/

Comments start with a /* character sequence and end the a */
Comments are remarks and are ignored by the compiler
Programmers include comments to clarify their program, document their work, and in general, make their programs more understandabl</span><span
class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt; font-style: italic;">e to other people and themselves
Good programmers write comments as they write the
code


Comments may span multiple lines (as in the example
above) or may be restricted to one line:

/* area = PI times R^2 */

Comments may also be embedded within a stateme</span><span
class="Normal--Char" style=" font-family: 'Times New Roman', 'Arial';
font-size: 14pt;">nt:

printf ( /* format */ "Hello world\n");

Many compilers support C++ style comments
In C++ a comment starts with a // and extends to the end of a line

// This is a typical C++ comment

printf ("Hello world\n); // say hello to the world

// printf ("Goodbye cruel world\n");

 

Dissection
of the Circle Program - Preprocessor Statements

#include <stdio.h>

Lines starting with a # character are preprocessor statements
Preprocessor statements begin with the # character and extend to the end of that logical line