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

• 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.