Ch7. Programming Language and Systems An Introduction to Informatics

1. Ch7. Programming Languageand SystemsAn Introduction to Informatics 2008. 12. 1 In-Bon Kuh GNU OSLab.

2. Source Program Lexical Analysis Tokens SymbolTables Syntax Analysis Intermediate Form Code Generation Target Program < Compiler Phases > An Introduction to Informatics

3. ... ... ifb = 15 thenx := (a + c) / xelsey := x ... ... ... ... LD B AC  B SUB N15 AC  AC - 15 BNZ L5 Go to else part, if AC ≠ 0 LD A AC  A ADD C AC  AC + C DIV X AC  AC / X (quotient) ST X X  AC B L6 Go to the end of statement L5 LD X AC  X ST Y Y  X L6 ... ... Compiler < Example of Source and Object Statements > An Introduction to Informatics

4. b, 15, = {Polish postfix of Boolean expression} IFJUMPL1 {Transfer on false.} x, a, c, +, x, /, := {True part of statement} JUMP L2 {Transfer of end of statement} L1: y, x, := {False part of statement} L2: 1: (=, b, 15, T1) {T1 (b = 15)} 2: (BNZ, T1, 6) {ifT1≠ 0 thengotoquadruple 6} 3: (+, a, c, T2) {T2  a + c} 4: (/, T2, x, x) {x  T2 / x} 5: (BR, 7, ,) {gotoquadruple 7} 6: (ST, y, x,) {y  x} 7: < Postfix Form > < Quadruples > An Introduction to Informatics