1. C++
First Steps

2. Overview C++ First Steps - General Data Types - Categories of Words
- The Three S’s
- Define Before Use
- End of Statement
- My First Program

3. defining a set of valid values and operations
Data Type
a description of data,
defining a set of valid values and operations
List of General Data Types:
- Integer: numbers without a decimal point
- Float: numbers with a decimal point
- Character: a single character
- String: a sequence of 0 or more characters

4. Data Type Q: What is meant by “defines operations”?
A: a Data Type defines which operators may be used on values of the type and how they work.
result 5 definition of + on integers
'2'+'3' result definition of + on characters

5. Categories of Words
The words and symbols found in a C++ program fall into the following categories:
- Reserved Words (Keywords)
- Identifiers
- Literals
- Comments
- Compiler Directives

6. Categories of Words Reserved Words (Keywords)
Words that already have a defined meaning in C++
including operators and symbols
Ex: + * / < <= << >> ( [

7. Categories of Words Identifiers
Words that are created and defined by the programmer.
Rules:
- Must start with a letter or underscore (_)
- The remainder may be letters, digits
or the underscore (_)
- Note: that means no spaces
- Identifiers are Case Sensitive

8. a data value with an implied data type
Categories of Words
Literals
a data value with an implied data type
Examples:
5 integer literal: digits with no decimal point
5.0 float literal: digits with a decimal point
'1' character literal: exactly one character between single quotes.
"a 12.0" string literal: 0 or more characters between double quotes. Must be on one line.

9. Categories of Words Escape Characters
The ASCII Table defines the binary codes for 256 possible characters.
Some characters are not found on a keyboard but are needed in some programming situations.
C++ provides Escape Characters for specifying such character literals.

10. Categories of Words Escape Characters
Inside quotation marks (literals), Escape Characters are identified by a backslash \ followed by a single character
The single character indicates which special character
Together these two characters are interpreted as one character

11. Categories of Words Escape Characters
\n Newline (go down to the next line)
\t Tab
\’ Single Quote (needed inside a char literal)
\” Double Quote (needed inside a string literal)
\\ Backslash
(there are more)

12. Categories of Words Escape Characters
cout << "Hello\t\"World\"\n\n\\BS\\\n";
Prints:

13. Categories of Words Comments Two forms:
Block Comment: anything between /* and */
May include multiple lines.
Line Comments: anything after // to the end of the line

14. Categories of Words Comments /* this is a block comment */ /*
This is also a block comment */
* traditionally more like this
// this is a line comment

15. Categories of Words Compiler Directives
Purpose: to direct the compiler to do something with the Source code before translation begins.
Start with # followed by a pre-defined word (no space), usually followed by something more.

16. Categories of Words Compiler Directives
Example: #include <iostream>
#include instructs the compiler to “copy/paste” a file into the Source code. It is followed by the name of the file.
When the file name is between < arrows >, this means “look in the C++ standard library”.

17. Categories of Words Compiler Directives
Example: #include <iostream>
iostream is a C++ library that defines cout, cin, the system() function and many other things.
It must be included in any source file that uses those items defined in it.

18. Categories of Words Compiler Directives
Compiler Directives are usually placed at the top of a source file
(not considering comments).

19. Syntax Semantics Style
The Three S’s
When learning new statements in C++,
we will discuss three major aspects:
Syntax
Semantics
Style

20. Rules defined by the language for writing statements
The Three S’s
Syntax
Rules defined by the language for writing statements
Violation of these rules causes a Syntax Error and the compiler is unable to translate the code.

21. Semantics The meaning of a statement: what it does.
The Three S’s
Semantics
The meaning of a statement: what it does.

22. Violation of these rules has no effect on the program.
The Three S’s
Style
Rules for writing statements that make the code easier for a programmer to understand
Violation of these rules has no effect on the program.

23. Style The Three S’s Examples: - Writing meaningful comments
- Creating descriptive identifier names
- Indentation and spacing
- Breaking a statement up over multiple lines (or not).

24. Warning to the Snakes! The Three S’s (Python programmers)
Indentation, spacing, and end-of-line affect the Syntax and Semantics of statements in Python
In C++ THEY DO NOT!**

25. Define Before Use
When compiling a source file, C++ begins with the first line and proceeds down, left to right.
Any identifier must be defined before it can be used, including those defined in standard libraries.
Example: #include<iostream> must be above the use of any identifiers it defines (ex: cout, system())
Violation of this rule results in the syntax error “identifier undefined”

26. In C++ the semicolon ; is used to indicate End of Statement

27. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }

28. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
Comment - has no effect on the program

29. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
Compiler Directive - this program uses the iostream library in C++. It is needed to define the word cout.

30. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
Instructs the compiler to use the "standard namespace". Without this, cout and other words would be "undefined".

31. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
main() - beginning of the program instructions. Execution always starts here.

32. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
Begin and End of main()'s block. Note the { may be on the end of the int main() line, or on a line by itself.

33. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
cout is used to print on the screen in a Console Application

34. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
The << operator is used to separate individual pieces of data to be printed. Here, only one string literal is printed.

35. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n" ;
system("pause");
return 0; }
A String Literal begins and ends with a double quote. This is literally what is printed on the screen.

36. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
The \n makes the cursor go down to
the next line after printing the !

37. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
This is a request to the OS (Windows) to execute the pause command, which prints "Hit any key to continue..." then waits for the user to respond.

38. First C++ Program // my first program #include <iostream>
using namespace std;
int main() {
cout << "Hello world!\n";
system("pause");
return 0; }
return 0; causes the program to exit main(), and so exits the program. It should always be the last line in main().

39. - Data Type - Categories of Words - The Three S’s - Define Before Use
Conclusion
- Data Type
- Categories of Words
- The Three S’s
- Define Before Use
- End of Statement
- My First Program

40. Vocabulary Term Definition Data Type
A description of data defining valid values and operations
Integer
A number without a decimal point
Float
A number with a decimal point
Character
A single character (letter, numeral, symbol)
String
A sequence of 0 or more characters
Reserved Word
Word (or symbol) that has a meaning already defined in the language
Keyword
(same as Reserved Word)
Identifier
Word created and defined by the programmer
Literal
Word (or symbol) that is a data value with an implied type
Comment
Programmer notes in the source that are not translated
Compiler Directive
Word(s) beginning with # that instruct the compiler to manipulate the source code before translating.

41. Vocabulary Term Definition Syntax
Rules for writing programs as defined by the language; violation causes a Syntax Error and the program cannot be compiled (translated)
Semantics
Meaning of a statement; what it does
Style
Rules for writing statements that make a program clearer to a programmer; violation has no effect on the translation or execution of the program