Organization for Block Structured Languages

Organization for Block Structured Languages:
  • The block structured language is a kind of language in which sections of source code is within some matching pair of delimiters such as “{“ and “}” or begin and end
  • Such a section gets executed as one unit or one procedure or a function or it may be controlled by some conditional statements (if, while, do-while)
  • Normally, block structured languages support structured programming approach
                Example: C, C++, JAVA, PASCAL, FORTRAM, LISP and SNOBOL
  • Non-block structured languages are LISP, FORTRAN and SNOBOL
Implementation of Symbol Table:
  • Each entry in the symbol table can be implemented as a record with several fields
  • The following data structures are used for organization of block structured languages:
                Linear List
                Self-Organizing List
                Hashing
                Tree Structure

Symbol table organization using Linear List:
  • A linear list of records is the easiest way to implement the symbol table
  • In this method, an array is used to store names and associated information
  • The new names are added to the symbol table in the order they arrive
  • The pointer “available” is maintained at the end of all stored records
  • To retrieve the information about some name we start from beginning of array and go on searching up to available pointer. If we reach at pointer available without finding a name we get an error “use of undeclared name”
  • While inserting a new name we should ensure that it is not already present. If it is already present then another error occurs, i.e., “Multiple Defined Name”.
Advantages:
  • It takes minimum amount of space
  • Additions are simple
  • Limitations
  • Higher access time
Linear List as follows:
Name 1
Information 1
Name 2
Information 2
.
.
.
.
.
.
.
.
Name n
Information n

Symbol Table organization using self-Organizing List:
  • In this method, symbol table is implemented using linked list. A link field is added to each record
  • We search the records in the order pointed by the link of link field
  • A pointer “First” is maintained to point to first record of the symbol table
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  • The reference to these names can be Name 3, Name 4, Name 2
  • When the name is reference or created, it is moved to the front of the list
  • The most frequently referred names will tend to be at the front of the list. Hence, access time to most frequently referred names wil be the least
Advantages
  • It takes minimum amount of space
  • Additions are simple
  • Limitation
  • Higher access time

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About Data Sciences by Venu

Hi, My name is Venugopala Chary and I'm Currently working as Associate Professor in Reputed Engineerng College, Hyderabad. I have B.Tech and M.tech in regular from JNTU Hyderabad. I have 11 Years of Teaching Experience for both B.Tech and M.Tech Courses.
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