Storing data

Getting data out

Data types

Ruby as a foundation

Program Variables

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Assigning a value to a variable

The variable name on the left side of the equal sign gets a value assigned to it.

– A value can be assigned to give a name to a number

LegalAge = 21– A variable name may be easier to remember than a number and

thus, help to make programming easier– imagine having to remember and type 568.245 when you

want to reference the number of milliliters per pint

mlperpint = 568.245

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Getting data out of variable

To use the value stored in a variable, use the name is if it were the value itself

– The value might be printed for display purposes

PRINT “The legal age is #{LegalAge}”– The value might be used for a calculation

legalBirthDate = DateToday - LegalAge– The value be used for a decision

IF age < LegalAge Then PRINT “too young”

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Numbers or Letters?

Because of the way computers store and manipulate data, different types of variables are used.

Use a numeric data type for math operations Data type can affect

– the amount of memory used– the way decimals are handled– The number of digits that can be stored– how rounding or fractional values are handled

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String Data Type

The letters, numbers, and symbols on the keyboard are called alphanumeric

string is often used as a shorter way of referring to alphanumerics.

Quotations marks surrounding text indicates string data.FirstName = “Petulla”

In VisualBasic, the words as string are used when the variable is defined.

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Data types in Ruby and other languages

For simplicity, in Ruby a variable is considered a string type by default if input is from a keyboard

– String values need to be converted to numeric before performing math.

– Floating point data type can also be specified by assigning a value with a decimal point, otherwise integer is assumed

mlPerPint! = 568.245– In VisualBasic the words as single are used when the variable is

first defined.

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Other Data Types in Ruby and symbol used

Values too large for Fixnum are automatically converted to Bignum—both are subclasses of integer

Integer– Whole numbers up to 1 less than the native machine

word are stored as Fixnum

Other number bases– Hexadecimal - precede value with 0x– Binary – precede value with 0b– Octal – precede value with 0

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Other Data Types in VisualBasic and symbol used

In addition to the data types supported by Ruby, VisualBasic has several, such as:

– Boolean - True or False– Char – single Unicode character followed by lowercase c

“A”c

– Decimal – up to 29 digits followed by D 59.99D

– Date – days since year 1 enclosed in # #1/1/2001 1:00 PM#

– Double ± 10308 followed by R– Object– can store and convert to other types

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