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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
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2 <HTML
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3 ><HEAD
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4 ><TITLE
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5 >Object Files</TITLE
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6 ><META
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7 NAME="GENERATOR"
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8 CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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9 REL="HOME"
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10 TITLE="LW Tool Chain"
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11 HREF="index.html"><LINK
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12 REL="PREVIOUS"
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13 TITLE="Libraries and LWAR"
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15 ><BODY
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20 VLINK="#840084"
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21 ALINK="#0000FF"
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22 ><DIV
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23 CLASS="NAVHEADER"
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24 ><TABLE
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25 SUMMARY="Header navigation table"
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29 CELLSPACING="0"
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30 ><TR
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31 ><TH
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32 COLSPAN="3"
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33 ALIGN="center"
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34 >LW Tool Chain</TH
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35 ></TR
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36 ><TR
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37 ><TD
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38 WIDTH="10%"
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39 ALIGN="left"
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40 VALIGN="bottom"
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41 ><A
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42 HREF="c718.html"
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43 ACCESSKEY="P"
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44 >Prev</A
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45 ></TD
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46 ><TD
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47 WIDTH="80%"
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48 ALIGN="center"
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49 VALIGN="bottom"
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50 ></TD
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51 ><TD
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52 WIDTH="10%"
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53 ALIGN="right"
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54 VALIGN="bottom"
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55 > </TD
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56 ></TR
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57 ></TABLE
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58 ><HR
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59 ALIGN="LEFT"
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60 WIDTH="100%"></DIV
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61 ><DIV
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62 CLASS="CHAPTER"
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63 ><H1
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64 ><A
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65 NAME="OBJCHAP"
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66 ></A
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67 >Chapter 6. Object Files</H1
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68 ><P
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69 >LWTOOLS uses a proprietary object file format. It is proprietary in the sense
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70 that it is specific to LWTOOLS, not that it is a hidden format. It would be
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71 hard to keep it hidden in an open source tool chain anyway. This chapter
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72 documents the object file format.</P
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73 ><P
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74 >An object file consists of a series of sections each of which contains a
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75 list of exported symbols, a list of incomplete references, and a list of
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76 "local" symbols which may be used in calculating incomplete references. Each
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77 section will obviously also contain the object code.</P
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78 ><P
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79 >Exported symbols must be completely resolved to an address within the
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80 section it is exported from. That is, an exported symbol must be a constant
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81 rather than defined in terms of other symbols.</P
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82 ><P
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83 >Each object file starts with a magic number and version number. The magic
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84 number is the string "LWOBJ16" for this 16 bit object file format. The only
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85 defined version number is currently 0. Thus, the first 8 bytes of the object
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86 file are <FONT
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87 COLOR="RED"
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88 >4C574F424A313600</FONT
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89 ></P
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90 ><P
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91 >Each section has the following items in order:</P
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92 ><P
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93 ></P
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94 ><UL
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95 ><LI
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96 ><P
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97 >section name</P
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98 ></LI
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99 ><LI
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100 ><P
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101 >flags</P
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102 ></LI
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103 ><LI
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104 ><P
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105 >list of local symbols (and addresses within the section)</P
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106 ></LI
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107 ><LI
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108 ><P
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109 >list of exported symbols (and addresses within the section)</P
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110 ></LI
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111 ><LI
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112 ><P
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113 >list of incomplete references along with the expressions to calculate them</P
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114 ></LI
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115 ><LI
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116 ><P
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117 >the actual object code (for non-BSS sections)</P
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118 ></LI
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119 ></UL
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120 ><P
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121 >The section starts with the name of the section with a NUL termination
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122 followed by a series of flag bytes terminated by NUL. There are only two
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123 flag bytes defined. A NUL (0) indicates no more flags and a value of 1
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124 indicates the section is a BSS section. For a BSS section, no actual
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125 code is included in the object file.</P
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126 ><P
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127 >Either a NULL section name or end of file indicate the presence of no more
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128 sections.</P
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129 ><P
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130 >Each entry in the exported and local symbols table consists of the symbol
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131 (NUL terminated) followed by two bytes which contain the value in big endian
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132 order. The end of a symbol table is indicated by a NULL symbol name.</P
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133 ><P
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134 >Each entry in the incomplete references table consists of an expression
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135 followed by a 16 bit offset where the reference goes. Expressions are
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136 defined as a series of terms up to an "end of expression" term. Each term
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137 consists of a single byte which identifies the type of term (see below)
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138 followed by any data required by the term. Then end of the list is flagged
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139 by a NULL expression (only an end of expression term).</P
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140 ><DIV
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141 CLASS="TABLE"
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142 ><A
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143 NAME="AEN805"
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144 ></A
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145 ><P
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146 ><B
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147 >Table 6-1. Object File Term Types</B
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148 ></P
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149 ><TABLE
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150 BORDER="1"
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151 FRAME="border"
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152 CLASS="CALSTABLE"
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153 ><COL><COL><THEAD
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154 ><TR
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155 ><TH
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156 >TERMTYPE</TH
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157 ><TH
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158 >Meaning</TH
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159 ></TR
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160 ></THEAD
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161 ><TBODY
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162 ><TR
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163 ><TD
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164 >00</TD
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165 ><TD
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166 >end of expression</TD
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167 ></TR
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168 ><TR
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169 ><TD
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170 >01</TD
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171 ><TD
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172 >integer (16 bit in big endian order follows)</TD
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173 ></TR
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174 ><TR
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175 ><TD
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176 >02</TD
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177 ><TD
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178 > external symbol reference (NUL terminated symbol name follows)</TD
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179 ></TR
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180 ><TR
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181 ><TD
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182 >03</TD
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183 ><TD
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184 >local symbol reference (NUL terminated symbol name follows)</TD
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185 ></TR
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186 ><TR
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187 ><TD
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188 >04</TD
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189 ><TD
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190 >operator (1 byte operator number)</TD
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191 ></TR
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192 ><TR
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193 ><TD
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194 >05</TD
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195 ><TD
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196 >section base address reference</TD
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197 ></TR
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198 ><TR
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199 ><TD
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200 >FF</TD
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201 ><TD
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202 >This term will set flags for the expression. Each one of these terms will set a single flag. All of them should be specified first in an expression. If they are not, the behaviour is undefined. The byte following is the flag. There is currently only one flag defined. Flag 01 indicates an 8 bit relocation.</TD
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203 ></TR
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204 ></TBODY
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205 ></TABLE
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206 ></DIV
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207 ><P
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208 >External references are resolved using other object files while local
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209 references are resolved using the local symbol table(s) from this file. This
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210 allows local symbols that are not exported to have the same names as
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211 exported symbols or external references.</P
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212 ><DIV
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213 CLASS="TABLE"
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214 ><A
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215 NAME="AEN835"
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216 ></A
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217 ><P
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218 ><B
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219 >Table 6-2. Object File Operator Numbers</B
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220 ></P
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221 ><TABLE
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222 BORDER="1"
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223 FRAME="border"
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224 CLASS="CALSTABLE"
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225 ><COL><COL><THEAD
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226 ><TR
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227 ><TH
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228 >Number</TH
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229 ><TH
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230 >Operator</TH
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231 ></TR
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232 ></THEAD
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233 ><TBODY
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234 ><TR
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235 ><TD
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236 >01</TD
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237 ><TD
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238 >addition (+)</TD
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239 ></TR
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240 ><TR
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241 ><TD
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242 >02</TD
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243 ><TD
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244 >subtraction (-)</TD
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245 ></TR
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246 ><TR
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247 ><TD
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248 >03</TD
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249 ><TD
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250 >multiplication (*)</TD
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251 ></TR
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252 ><TR
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253 ><TD
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254 >04</TD
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255 ><TD
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256 >division (/)</TD
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257 ></TR
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258 ><TR
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259 ><TD
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260 >05</TD
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261 ><TD
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262 >modulus (%)</TD
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263 ></TR
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264 ><TR
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265 ><TD
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266 >06</TD
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267 ><TD
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268 >integer division (\) (same as division)</TD
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269 ></TR
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270 ><TR
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271 ><TD
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272 >07</TD
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273 ><TD
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274 >bitwise and</TD
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275 ></TR
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276 ><TR
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277 ><TD
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278 >08</TD
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279 ><TD
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280 >bitwise or</TD
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281 ></TR
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282 ><TR
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283 ><TD
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284 >09</TD
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285 ><TD
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286 >bitwise xor</TD
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287 ></TR
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288 ><TR
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289 ><TD
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290 >0A</TD
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291 ><TD
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292 >boolean and</TD
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293 ></TR
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294 ><TR
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295 ><TD
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296 >0B</TD
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297 ><TD
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298 >boolean or</TD
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299 ></TR
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300 ><TR
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301 ><TD
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302 >0C</TD
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303 ><TD
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304 >unary negation, 2's complement (-)</TD
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305 ></TR
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306 ><TR
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307 ><TD
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308 >0D</TD
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309 ><TD
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310 >unary 1's complement (^)</TD
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311 ></TR
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312 ></TBODY
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313 ></TABLE
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314 ></DIV
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315 ><P
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316 >An expression is represented in a postfix manner with both operands for
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317 binary operators preceding the operator and the single operand for unary
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318 operators preceding the operator.</P
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319 ></DIV
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320 ><DIV
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321 CLASS="NAVFOOTER"
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334 VALIGN="top"
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337 ACCESSKEY="P"
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338 >Prev</A
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346 ACCESSKEY="H"
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347 >Home</A
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360 >Libraries and LWAR</TD
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