Chapter 4

• Assembly language


  A mnemonic system for representing machine instructions
• Assembly language


  • One-to-one correspondence between machine instructions and assembly instructions
  • Programmer must think like the machine
  • Inherently machine-dependent
  • Converted to machine language by a program called an assembler
• Third Generation Language


  • Uses high-level primitives
  • Machine independent (mostly)
  • Examples: C++, FORTRAN, COBOL
  • Each primitive corresponds to a sequence of machine language instructions
  • Converted to machine language by a program called a compiler
• Data Types


  • Integer: Whole numbers
  • Real (float): Numbers with fractions
  • Character: Symbols
  • Boolean: True/false
• Variable Declarations


  • float Length, Width;
  • int Price, Total, Tax;
  • char Symbol;
• Declarative Programming


  • Resolution: Combining two or more statements to produce a new statement (that is a logical consequence of the originals)
  • Unification: Assigning a value to a variable so that two statements become "compatible"
• Resolution


  • (P OR Q) AND (R OR Q) resolves to (P OR R)
• Resolvent: A new statement deduced by resolution
• Clause form: A statement whose elementary components are connected by the Boolean operation OR
• To find if Q is consistent with the following set of statement we introduce ¬Q
• Polish strings uses tree structure and stack
• The translation process


  1. Parse tree

  2. Polish strings
• Polish strings


  • A + B