meta languages railroad diagrams student version
DESCRIPTION
Student Version of Meta Languages Railroad diagrams for uploading to wiki, without answers.TRANSCRIPT
Kelly Bauer
META LANGUAGES
WHY?
Describes the syntax of a computer language
Rules that govern the arrangement of elements in a language
eg. The ran catORThe cat ran
WHY NOT JUST LEARN THE LANGUAGE?
Programming languages are very complex. You cant possibly know every way to do everything that you want.
The likelihood is that you won’t program in the language you learn.
Allows language specifications be understood by programmers and allows more learnability between languages
2 BASIC FORMS
Railroad diagram (aka syntax structure diagrams)
BNF/EBNF
RAILROAD DIAGRAMS
ELEMENTS
Allowable Paths
PRE DEFINED LANGAUGE ELEMENTS
Eg, letter, sentence, program, variable name
Variable
FIXED ELEMENTS
Reserved words, eg, Dim, -+, 0, 1
Dim
As
THE ELEMENTS CAN BE COMBINED TO GIVE OPTIONS
Eg, A Boolean Constant
T
F
OR TO REPEAT ELEMENTS
Eg, A word
Letter
AND THESE CAN THEN BE COMBINED Eg, a number that can be either
positive or negative
_
Digit
TEXTBOOK
Pg 168 Defines the Winston language in railroad diagrams
Is the following legitimate conditions
Abcd = +99
ABCD = +99
Abcd is a legitimate identifier, because it starts with an uppercase followed by a number of lower case
+99 is a legitimate constant because it is a negative followed by a number of digits
The statement follows the correct order of
Identifier condition constantDavis, Sam (2008) Software Design and Development: The Preliminary Course, Parramatta Education Centre, Sydney
Complete 2nd activity on pg 168
TEXT ACTIVITY
AN EXAMPLE
IN VISUAL BASIC
Construct a railroad diagram to describe a best practice, legal variable declaration.
Should follow the following structure: Dim Public or Private Variable Name As
Data Type
DATA TYPE
In Visual Basic, this can be Boolean, Byte, Char, Date, Time, Decimal, Double, Int, Long, Object, Short, Single
VARIABLES IN VB
Must begin with an uppercase letter Can be lower or upper case or digits
after first letter
1
2
3
4
5
6
7
8
9
0
CONSTRUCT A RAILROAD DIAGRAM OF A LEGAL IF STATEMENT FOR VISUAL BASIC
HW
SYLLABUS SECTIONS?
IMAGES FROM
http://www.trs-80.com/trs80-mag-books.htm http://homepages.cwi.nl/~dik/english/codes/punched.html http://www.borislavdopudja.net/en/writings/cheating_google/