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C++ Basics Tutorial 5

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C++ Basics Tutorial 5

Constants

- Literal Constants
- Defined Constants
- Declared Constants

- Most easy to see and most obvious constants

- Integer Numerals
- Floating-Point Numerals
- Boolean literals
- Character literals
- String literals

- A number without decimal points (duh!)
- Examples: 23, 56, 8…

- In C++, expressing numerical constants does not require any special character like “”.
- Integer numerals can be defined in other numeral forms like octal or hexadecimal.
- 255 Decimal Value
- 0377 Octal value
- 0xff Hexadecimal Value

All represent same number

- To denote an octal number(Base 8 number) start the number with 0 (zero)
- To denote a hexadecimal value(base 16 number) start with 0 x (zero “x”)
- Write normally for decimal numerical(base 10) system value.
- Force int to be unsigned by adding u(or U) at the end of number. (Ex: 19U) or l(or L) to make it long( 19L or 19UL)

- To represent number with decimal or exponents
- A decimal point “.” or a “e” can be added to represent the number, where e means to the “power by 10” to number after e.
- Also can have both “e” and “.”
- Example: 3.14 Value of Pi
5.97e24(Mass of earth) = 5.97 x 10 ^ 24

or 1.67e-27(Mass of proton) = 1.67 x 10 ^ -27

- Force number to be long double add L or l, to force number to be float add f or F in the end of the number
- E or e both are same. C++ is not case sensitive in this case.

- Only two boolean literals in C++: true or false.
- Can be represented by bool data type.

- One character. Example: ‘a’, ‘b’, ‘A’ etc…
- To represent character literals we put them inside single quotes. This is done to differentiate them from possible variable identifiers that we might define in the program.
- If you just write 1 it is numerical literal. But ‘1’ makes it character literal.
- ‘a’ is a character literal where as just a is a variable identifier named a.

- Combination of characters.
- Inside double quotes “”.
- Example “Dean”

- Characters and string both can have a special character called escape character.
- Impossible or at least difficult to express otherwise
- Precede by a backslash(\) and a character.
- Example: \n New Line, \t Tab
- ‘\n’ or ‘\t’ or “LineOne\nLineTwo\nLineThree”
- “\”DoubleQuote\”” = “DoubleQuote” when you print.

- \n Newline
- \t tab
- \r carriage return
- \v vertical tab
- \b backspace
- \f form feed
- \a alert beep
- \’ single quote(‘)
- \” Double quote(“)
- \? question mark(?)
- \\ backslash(\)

- Using something called preprocessor directive
- Use #define preprocessor directive
- Define constant that will be used frequently.
- Example:
#define PI 3.14159

#define NEWLINE ‘\n’

- This now have defined two constants called PI and NEWLINE. Now you can use PI and NEWLINE as other constants we learned earlier.
- Due to #define the C++ compiler literally replaces all the occurrences of PI and NEWLINE with assigned value(3.14159 or ‘\n’)

- Example:

- A directive is not a C++ statement. It is interpreted by the preprocess that happens before even looking at the code of the program. So these directive does not need to have a semicolon in the end.
- Directives start with #. Applies to #include as well.

- Using const prefix with specific data type you make a variable unchangeable throughout the program.
- Example:
constint a = 23;

const char newline = ‘\n’

- Example:
- The are completely regular variables except that you cannot modify these after you initialize.

- Next Chapter: We will talk about operators
- Then: Basic input/ output.
- End of Basics.

- Then to Control structures / Functions