Data Types

• A variable's data type determines what operations are allowed with the variable

• It also determines the range and type of values that can be stored

• In C++ all variables must be declared ahead of time

• The variable types allow code to be more efficient, working with numbers the same way as the processor

• Some compilers support greater ranges of values, but these are the minimum values.

Modifiers

• "Modifies" the properties of the data type in order to make it better fit a particular situation

  • Modifiers for int: signed, unsigned, short, long

  • Modifiers for char: signed, unsigned

  • Modifiers for double: long

Signed Variables

• Signed refers to weather or not the variable stores information about if the value is + or -

  • Think absolute value

• The first bit of the data is interpreted as a 0 or 1 which corresponds to a + or -

• "unsigned x" is the same as "unsigned int x"

Integers

• Can't hold fractions or decimals

• Used for controlling loops and conditional statements and counting.

• If not otherwise specified, they are assumed to be signed.

Floating-Point Variables

• Allow for decimals unlike integers

• Allow for very large or small numbers

• Basically store the value in scientific notation

• Two types: Double and Float

• Double can hold 10 times the value of float

• Double is the most common variable type because most libraries are written assuming variables are the double type

Code: Double Data Type

Boolean

• Stores only 1 or 0 which correspond to "true" or "false"

• Any non-zero value is assumed to mean "true"

Code: Prime Numbers

Void

• Valueless expression

Literals

• Essentially constants

• Can be numbers or strings

Numerical Literals

• Must be expressed as a decimal

  • No fractions

• Can be in scientific notation

• Compiler can automatically chose the most efficient data type for the value you provide.

• Data type can also be manually chosen with a suffix on the value

• Values can be stored in different number systems

  • Octal

  • Hexadecimal

String Literals

• A set of characters enclosed in double quotes

• There is no string data type, instead strings are stored as an array of characters

Character Escape Sequences

• A way of typing special characters

• Also called backslash character constants

Declaring Variables

• General form is "type varName;"

  • type is the data type

  • varName is the variable's name

• Variables can never change data type

• You can also declare a value when declaring the variable

  • type varName = "value";

• Variables can be initialized at any time during the program

  • Called Dynamic Initialization

Type Conversion

• Bits can be gained and lost if different types are incorrectly converted to eachother
• Need to use a "cast" to change data type without data loss

(type) expression

(float) x/2