DPANSA2.HTM (3172B)
1 <HTML><HEAD> 2 <TITLE>DPANS94</TITLE> 3 <link disabled rel="stylesheet" href="mpexc6.css"> 4 <style>@import url(mpexc6.css);</style> 5 </head> 6 7 <BODY> 8 <table width=100%> 9 <tr> 10 <td align=left> 11 <a href=dpansa1.htm><img src=left.gif 12 width=26 height=26 align=ALIGN border=0></a> 13 <a href=dpansa3.htm><img src=right.gif 14 width=26 height=26 align=ALIGN border=0></a> 15 </td> 16 <td align=right> 17 <a href=dpans.htm#toc><img src=up.gif 18 width=26 height=26 align=ALIGN border=0></a> 19 <a name=A.2>Table of Contents</a> 20 </td> 21 </tr> 22 </table> 23 <p> 24 <hr size=4> 25 26 27 <H2>A.2 Terms and notation</H2> 28 29 30 <hr> 31 <a name=A.2.1> 32 <H3>A.2.1 Definitions of terms</H3> 33 </a> 34 35 <DL> 36 <DT><b>ambiguous condition</b> 37 <DD>The response of a Standard System to an ambiguous condition is left to 38 the discretion of the implementor. A Standard System need not 39 explicitly detect or report the occurrence of ambiguous conditions. 40 <p> 41 <DT><b>cross compiler</b> 42 <DD>Cross-compilers may be used to prepare a program for execution in an 43 embedded system, or may be used to generate Forth kernels either for the 44 same or a different run-time environment. 45 <p> 46 <DT><b>data field</b> 47 <DD>In earlier standards, data fields were known as <B>parameter fields</B>. 48 <P> 49 50 On subroutine threaded Forth systems, everything is object code. There 51 are no traditional code or data fields. Only a word defined by 52 <a href=dpans6.htm#6.1.1000>CREATE</a> 53 or by a word that calls 54 CREATE has a data field. Only a data field 55 defined via CREATE can be manipulated portably. 56 <p> 57 <DT><b>word set</b> 58 <DD>This Standard recognizes that some functions, while useful in certain 59 application areas, are not sufficiently general to justify requiring 60 them in all Forth systems. Further, it is helpful to group Forth words 61 according to related functions. These issues are dealt with using the 62 concept of word sets. 63 64 <P> 65 66 The <B>Core</B> word set contains the essential body of words in a Forth 67 system. It is the only <B>required</B> word set. Other word sets 68 defined in this Standard are optional additions to make it possible to 69 provide Standard Systems with tailored levels of functionality.</DL> 70 71 <P> 72 73 <hr> 74 <a name=A.2.2> 75 <H3>A.2.2 Notation</H3> 76 </a> 77 78 79 <hr> 80 <a name=A.2.2.2> 81 <H4>A.2.2.2 Stack notation</H4> 82 </a> 83 84 The use of -sys, orig, and dest data types in stack effect diagrams 85 conveys two pieces of information. First, it warns the reader that many 86 implementations use the data stack in unspecified ways for those 87 purposes, so that items underneath on either the control-flow or data 88 stacks are unavailable. Second, in cases where orig and dest are used, 89 explicit pairing rules are documented on the assumption that all systems 90 will implement that model so that its results are equivalent to 91 employment of some stack, and that in fact many implementations do use 92 the data stack for this purpose. However, nothing in this Standard 93 requires that implementations actually employ the data stack (or any 94 other) for this purpose so long as the implied behavior of the model is 95 maintained. 96 97 <P> 98 99 <hr> 100 <A href=dpans.htm#toc><IMG src="up.gif" ></A> Table of Contents 101 <BR> 102 <A href=dpansa3.htm><IMG src="right.gif" ></A> 103 Next Section 104 <P> 105 </BODY> 106 </HTML>