# C++ Basics Tutorial 5 - PowerPoint PPT Presentation

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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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C++ Basics Tutorial 5

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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

### Types of literal constants

• 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

• 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

• 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.

### Floating Point literals

• Only two boolean literals in C++: true or false.

• Can be represented by bool data type.

### Boolean literals

• 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.

### Character literals

• Combination of characters.

• Inside double quotes “”.

• Example “Dean”

### String literals

• 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

• \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(\)

### Few list of escape characters:

• 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’)

### Defined constants

• 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.

### Directive

• Using 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)

• Next Chapter: We will talk about operators

• Then: Basic input/ output.

• End of Basics.

• Then to Control structures / Functions