An integrated development environment (IDE) helps develop (code editing, building, testing, debugging) programs. As C language is very widely used a lot of such tools exist. The recommended IDE for this subject is a free tool Code::Blocks that is also installed on the computers of the Students' Computer Center.
Start the Code::Blocks program. Choose File menu/New/Project… submenu. Create a new project following the pictures below. Pay attention to the details.
- The type of the project should be
Console application. ClickGo.
- The next page is to select the language. Of course it is C.
- Then Code::Blocks will let you name your project (e.g. first). In the next line select a folder to create your project in. If it is empty, hit the
...button and browse to Documents in your home folder. (Remember this path!) Important: neither the folder name, nor the path should contain space or accented letters!
- In the fourth window there is usually nothing to change. Compare to the picture.
- Your new project is ready. The files of the project can be seen in the „Management” panel. Opening the „Sources”
folder you can find the main (and only) program module:
main.c. It contains a Hello World program.
Code::Blocks created the new project with a simple Hello World program. If you use a different IDE paste this C program (double-clicking in the code selects all the program):
#include <stdio.h>
int main(void)
{
printf("Hello world!\n");
return 0;
}
Look at the code in the editor panel of the IDE: it appears in different colours. Which words are coloured? What is the advantage of this feature? Easier to read the code and spot certain mistypings. Many IDEs mark the corresponding pair for the brackets and parentheses.
The executable program
Our own program created by the IDE works the same way as other command line applications: there is an .exe file, and its output can be redirected. Clicking the „Build and run” (green play + yellow gear symbol) button or selecting the Build/Build and run submenu will run your program. First the code is compiled then the executable is started. The result should look like this.
Find the compiled executable on the comuter. It must be in the folder selected at the project creation.
Open a command window (cmd) and navigate (cd) to that folder. Beside main.c you will see some other files. There will be a folder named bin and another folder Debug in it. And in this folder you can see the executable of your first project (first.exe). Start it!
The compiled program is a file that contains machine instructions to print the required text, plus a few other things meaningful for the operating system. This is the executable (frequently called binary). It is not meaningful for humans, look at the content using the type
(cat under Linux) command.
Hint: if you forgot the name of the folder it is easy to locate it.
Right-click on a file in the „Management/Project” panel of Code::Blocks (like main.c) and select „Properties…”: at „File name (absolute)” property you will see the file name with full path:
C:\Documents and Settings\Name\Dokumentumok...– Windows ≤5 (XP).C:\Users\Name\...– Windows ≥6 (Vista)./home/name/...– Linux.
Files of the IDE project
Examine the other files in the project folder! Especially main.c and first.cbp (this has the name of the actual project). You can open them in notepad(notepad first.cbp) or simply type/cat/more them.
The main.c file contains your program:
#include <stdio.h>
int main(void)
{
printf("Hello world!\n");
return 0;
}
The project file first.cbp contains data and settings of the project, maintained by CodeBlocks:
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<CodeBlocks_project_file>
<FileVersion major="1" minor="6" />
<Project>
<Option title="first" />
<Option pch_mode="2" />
<Option compiler="gcc" />
...
Note. Windows explorer by default hides file extensions (instead of main.c you only see main). This mighty might be advantageous for office workers but it is disastrous for the rest of the world, especially for programmers. You are encouraged to change this behaviour on your own computer.
Redirecting the output
Test output redirection using the > character for your first program. Redirect output to hello.txt then print the file using the type command!
Obviously your program behaves exactly the same way as any other command line program. Redirection is a feature of the operating system and does not require any modification in your program. These programs are called console or command line applications; remember this is the type we selected during the creation of our project.
Task: Write a program that calculates how many cans of paint must be purchased to coat every (outer) surface of a cylindrical container. You must define variables of appropriate type, read in and print out values.
The height and the diameter of the cylinder is known. Yield of the paint: one can of paint is sufficient for a surface area of 2 m2.
Paint the container Height? 2 Diameter? 1.2 4.900885 can(s) of paint needed.
You can use an approximate value of 3.14159265 for Pi. If your program delivers different result re-check your formulae.
Format of the printout
A millionth of a can is not relevant but rather disturbing piece of information. To make the printout human friendly it is wise to round the printed value to one decimal digit following the decimal point: in printf change %f to %.1f.
4.9 can(s) of paint needed.
Solution
#include <stdio.h>
int main(void) {
double diameter, height;
printf("Container painting\n\n");
printf("Enter height: ");
scanf("%lf", &height);
printf("Enter diameter: ");
scanf("%lf", &diameter);
double radius = diameter/2;
double cans = (2*radius*radius*3.14159265 + height*2*radius*3.14159265) / 2;
printf("\nNumber of cans to buy: %f\n", cans);
return 0;
}