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C++ Basics Tutorial 5. Constants. Literal Constants Defined Constants Declared Constants. Topics Covered. Most easy to see and most obvious constants. Literal constants. Integer Numerals Floating-Point Numerals Boolean literals Character literals String literals.

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Topics covered

Topics Covered



Types of literal constants

  • Integer Numerals

  • Floating-Point Numerals

  • Boolean literals

  • Character literals

  • String literals

Types of literal constants


Integer numerals

  • 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

Integer Numerals


Decimal octal hexadecimal signed and unsigned representation

  • 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)

Decimal, Octal, hexadecimal, signed and unsigned representation


Floating point literals

  • To represent number with decimal or exponents with 0 (zero)

  • 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.

Floating Point literals


Boolean literals

  • Only two with 0 (zero)boolean literals in C++: true or false.

  • Can be represented by bool data type.

Boolean literals


Character literals

  • One with 0 (zero) 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.

Character literals


String literals

String literals


Escape characters

  • 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.

Escape Characters


Few list of escape characters

  • \n called escape character.  Newline

  • \t  tab

  • \r  carriage return

  • \v  vertical tab

  • \b  backspace

  • \f  form feed

  • \a  alert beep

  • \’  single quote(‘)

  • \”  Double quote(“)

  • \?  question mark(?)

  • \\  backslash(\)

Few list of escape characters:


Defined constants

  • Using something called preprocessor directive called escape character.

  • 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’)

Defined constants


Directive

Directive


Declared constants const

  • Using 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.const prefix with specific data type you make a variable unchangeable throughout the program.

    • Example:

      constint a = 23;

      const char newline = ‘\n’

  • The are completely regular variables except that you cannot modify these after you initialize.

Declared Constants (const)


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  • Next Chapter: We will talk about operators 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.

  • Then: Basic input/ output.

    • End of Basics.

  • Then to Control structures / Functions

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