Sdd Syntax Descriptions

Sdd Syntax Descriptions

• 1.
  Implementing Software SolutionsLanguage Syntax Required for Software Solutions
• 2.
  What is aMetalanguage? Metalanguages provide an understanding of rules implemented into programming languages. They represent a languages syntax which is used like a checklist when compiling a program to remove errors before execution takes place.
• 3.
  Why Do WeNeed Them? Computers operate in an environmnet full of rules. The use of syntax descriptions enables the computer and programmer to understand the boundaries of its environment. All data types, data structures and control structures used must have their own set of syntax developed to adhere to.
• 4.
  Types of Metalanguages?BNF or EBNF – Which is a text based description of syntax. Railroad Diagram – Is the graphical based description which is easier to understand.
• 5.
  BNF Symbols Isdefined as :: = Indicates choice between elements | Non terminal symbol < > Meaning Symbol
• 6.
  EBNF Symbols Enclosesoptional elements [ ] Encloses elements to be repeated { } Is defined as = Indicates choice between elements | Non terminal symbol < > Meaning Symbol
• 7.
  Railroad Symbols Predefinedelement Fixed element Path lines Meaning Symbol
• 8.
  Activity 1 Considerthe following EBNF diagram. <Digit> = 1 | 2| 3 <Number> = <Digit> * <Digit> <Sum> = {<Number>} – {<Number>} Identify which of the following statements are legal and illegal. Sum = (1 * 2) – (2 * 3) Sum = (1 * 4) – (2 * 3) Sum = (1 * 2) – (2 + 3)
• 9.
  Activity 1 Considerthe following Railroad diagram. Identify which of the following statements are legal and illegal. String = 5a$ String = a$ String = aa43 String = $b56 String = aaac11bc$ String Letter Number Letter $
• 10.
  Data Structure SyntaxArrays The declaration of an array is: Arrayname(5) Therefore, the syntax description would be: <Digit> = 0 | 1 | 2 …| 9 <Letter> = a | b | c … |z <Index> = {<Digit>} <Arrayname> = {<Letter>} <Array> = <Arrayname> (<Index>)
• 11.
  Data Structure SyntaxArrays So therefore if we typed in our code the following processes would be incorrect: Dogs (10) cat [1] trees (index)
• 12.
  Data Structure SyntaxMultidimensional Arrays The declaration of a multidimensional array is: Arrayname(Digit, Digit) Using this knowledge create a set syntax descriptions in railroad format for the above multidimensional array.
• 13.
  Data Structure SyntaxArray of Records Below is an example of a Array of Records Create a set of syntax descriptions for an Array of records using EBNF 12 Ben 11 John Age Name
• 14.
  Activity 2 Thefollowing EBNF describes the rules for an array of records. <Digit> = 1 | 2| 3…| 9 <Ucharacter> = A | B | C …..| Z <LCharacter> = a | b | c ……| z <Character> = <UCharacter> | <LCharacter> <Boolean> = [Y|N] | [T|F] <Fieldname> = {<Character>} <Fieldentry> = {<Character> | <Digit> | <Boolean>} <Record> = <Fieldname> {<Fieldentry>} <Arrayofrecords> = <Record> {<Record>}
• 15.
  Activity 2 Identifywhether the following are valid or invalid. a) b) c) 17 Dina Andys Age First Name Surname 78 Case 25 17 Ball 12 Cost Item ID1 F 23/4/02 John T 25/4/99 Jenny Medication Visit Patient
• 16.
  Activity 2 Belowis a VB statement for opening a file via random access. Open “MYFIL.FIL” For Random AS FileNum Len = Max Using either EBNF or Railroad create a set of syntax diagrams for this procedure.
• 17.
  Answer <Digit> =1 | 2| 3…| 9 <Ucharacter> = A | B | C …..| Z <LCharacter> = a | b | c ……| z <Character> = <UCharacter> | <LCharacter> <Variable> = {<Character>} <Filenumber> = {<Digit>} <Accesstype> = Random | Sequential <Pathname> = “ {<Character>} . {<Character} “ <Fileaccess> = Open <Pathname> For <Accesstype> As <Filenumber> Len = <Variable>