Feb13 - CSE262 Programming Languages Instructor Dr Liang...

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Unformatted text preview: CSE262: Programming Languages Instructor: Dr. Liang Cheng Department of Computer Science and Engineering P.C. Rossin College of Engineering & Applied Science Lehigh University February 13, 2007 Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Outline ¡ Recap ¡ Scope (Sections 5.8-5.10) ¡ Data types (Chapter 6) ¡ Summary and homework Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 You should now be able to … ¡ Describe static scope and dynamic scope; ¡ Find references to variables in static- scoped or dynamic-scoped languages; and ¡ Decide referencing environments. Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Scope of a Variable ¡ The range of statements where a variable is visible or can be referenced ¡ Static scoping / lexical scoping ¡ Algol 60, C, Pascal, C++, Java, Scheme, … ¡ Dynamic scoping ¡ LISP, Common LISP and Perl support both Scope ¡ Static scope ¡ Dynamic scope ¡ Scope and lifetime ¡ Referencing env variable: name, address, value, type, lifetime, scope Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Referencing Environments ¡ The collection of all names that are visible in the statement ¡ In a static-scoped language, it is the local variables plus all of the visible variables in all of the enclosing scopes ¡ In a dynamic-scoped language, the referencing environment is the local variables plus all visible variables in all active subprograms Scope ¡ Static scope ¡ Dynamic scope ¡ Scope and lifetime ¡ Referencing env variable: name, address, value, type, lifetime, scope Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Outline ¡ Recap ¡ Data types (Chapter 6) ¡ Summary and homework Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Data Types ¡ A data type defines a collection of data objects and a set of predefined operations on those objects ¡ Primitive data types ¡ Character string types ¡ User-defined ordinal types ¡ Array types ¡ Record types ¡ Union types ¡ Pointer types Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Integer ¡ There may be as many as eight different integer types in a language ¡ Ones-complement notation ¡ Twos-complement notation Primitive data types ¡ Integer ¡ Floating point ¡ Decimal ¡ Boolean ¡ Character Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Floating Point ¡ Languages for scientific use support at least two floating-point types ¡ IEEE Std 754: 00111110001000000000000000000000 ¡ v = (sign bit) × 2 Exponent-127 × (1.Fraction) 2 ¡ Fraction: precision; exponent & fraction: range Primitive data types ¡ Integer ¡ Floating point ¡ Decimal ¡ Boolean ¡ Character Instructor: Dr. Liang Cheng CSE262: Programming Languages 02/13/07 Decimal ¡ For business applications ¡ COBOL, C# ¡ Store a fixed number of decimal digits (binary coded decimal) ¡ 1 digit/byte (BCD) or 2 digits/byte (packed BCD) ¡ 27 => 00000010 00000111 or 0010 0111...
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This note was uploaded on 08/06/2008 for the course CSE 262 taught by Professor Cheng during the Spring '07 term at Lehigh University .

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Feb13 - CSE262 Programming Languages Instructor Dr Liang...

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