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cpp_lesson01 [2019/02/08 23:31]
cpp_lesson01 [2017/11/11 22:47] (current)
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 +===== Lesson 1: Hello World! =====
 +
 +==== Reading ====
 +
 +Before you begin, please read this article: [[http://​www.cplusplus.com/​doc/​tutorial/​program_structure/​|Structure of a Program]]
 +
 +==== Writing the Program ====
 +
 +In the editor of your choice, please write the following code. **Note:** The bluefish editor version 2.02 allows for an automatic structuring of a c++ program.
 +
 +<​code>​
 +// My first c++ program
 +#include <​iostream>​
 +using namespace std;
 +int main ()
 +{
 +   cout << "Hello World!";​
 +   ​return 0;
 +}
 +</​code>​
 +
 +**Note:** It is important to either read character by caracter or set your punctuation level to all in your Orca preferences for your editor.
 +
 +==== Explanations ====
 +
 +  - The first line of the program is a comment. The program will stop reading the line when it encounters "​%%//​%%"​ (two slashes).
 +  - We include input/​output preprocessing.
 +  - We declare standard global variables.
 +  - We leave a blank line. This is not manditory but it is a convention for readability.
 +  - We define the main function. This is where the program begins. **Note:** The word main is followed by a pair of brackets "​()"​. These are rounded brackets. Americans call these parenthesies.
 +  - We write a left-brace %%({%%). All functions are enclosed by braces.
 +  - We print our message to the screen. Notice the two left pointing arrows (less than characters <<). These tell the program to insert the words "Hello World" into the standard output stream. **Note:** The statement ends with a semicolon (;). All statements end with a semicolon.
 +  - We set a return code of zero (0) and exit the main function.
 +  - We end the main function with a right-brace (}).
 +
 +==== Compiling the Program ====
 +
 +Although not absolutely necessary, save your program with the "​cpp"​ extension. We assume, for this exercise, you have named your program
 +
 +<​code>​
 +hello1.cpp
 +</​code>​
 +
 +and that it is stored in your home folder.
 +
 +To compile "​hello1.cpp",​ at a terminal or console prompt, type:
 +
 +<​code>​
 +c++ hello1.cpp
 +</​code>​
 +
 +If your prompt returns with no messages, your program has compiled successfully. Otherwise, you will need to correct your code and compile the program again.
 +
 +==== Run Your Program ====
 +
 +Your compiled program is in a file called
 +
 +<​code>​
 +a.out
 +</​code>​
 +
 +To run your program type:
 +
 +<​code>​
 +./a.out
 +</​code>​
 +
 +You may, of course, rename your program to something more meaningful than "​a.out"​. It will also save your compiled program if you rename it; otherwise, the next compile you do will overwrite it.
 +
 +**Note:** The "​./"​ tells the operating system you understand you are executing a program.
 +
 +==== Formatting Your Output ====
 +
 +If we want to write more information to the screen, we may also want to format it. We can edit the line which begins "cout <<"​ to read as follows:
 +
 +<​code>​
 +cout << "Hello World" << endl;
 +</​code>​
 +
 +This will put an end-of-line character in our output stream. Now our prompt will appear on a separate line from our message to the world.
 +
 +==== Assignment ====
 +
 +  - Write a new program which will display the following message on a line of its own:<​code>​
 +I am a c++ program.
 +</​code>​
 +  - Read the article [[http://​www.cplusplus.com/​doc/​tutorial/​variables/​|Variables,​ Data Types]]