w04_Assembly_Language_Basics

要使用Basic编译器编译Basic程序，需要遵循以下步骤：
1. 安装Basic编译器：首先，您需要安装支持Basic语言的编译器。

例如，FreeBASIC
是一个流行的Basic编译器，可以在其官方网站上获得最新版本的编译器。

2. 编写Basic程序：使用您喜欢的文本编辑器创建一个扩展名为`.bas`的Basic源代码文件。

在该文件中编写您的Basic程序代码。

3. 打开终端或命令提示符：打开终端（在Linux和Mac上）或命令提示符（在Windows上）。

4. 切换到Basic编译器的安装目录：在终端或命令提示符中，使用`cd`命令切换到Basic编译器的安装目录。

例如，在FreeBASIC中，可能需要切换到FreeBASIC的安装目录。

5. 编译Basic程序：使用以下命令来编译Basic程序：
```
fbc your_program.bas
```
其中，`your_program.bas`是您编写的Basic程序的文件名。

6. 运行编译后的程序：完成编译后，您可以运行生成的可执行文件来执行Basic程序。

在终端或命令提示符中，输入生成的可执行文件的名称，并按回车键执行。

请注意，具体的步骤可能会因使用的Basic编译器而有所不同。

以上步骤提供了一个一般性的指导，您可能需要根据您使用的编译器的文档或说明进行适当的调整。

x86Assembly Language ReferenceManual Sun Microsystems,Inc.4150Network CircleSanta Clara,CA95054U.S.A.Part No:817–5477–10January2005Copyright2005Sun Microsystems,Inc.4150Network Circle,Santa Clara,CA95054U.S.A.All rights reserved.This product or document is protected by copyright and distributed under licenses restricting its use,copying,distribution,and decompilation.No part of this product or document may be reproduced in any form by any means without prior written authorization of Sun and its licensors,if any. Third-party software,including font technology,is copyrighted and licensed from Sun suppliers.Parts of the product may be derived from Berkeley BSD systems,licensed from the University of California.UNIX is a registered trademark in the U.S. and other countries,exclusively licensed through X/Open Company,Ltd.Sun,Sun Microsystems,the Sun logo,,AnswerBook,AnswerBook2,and Solaris are trademarks or registered trademarks of Sun Microsystems,Inc.in the U.S.and other countries.The OPEN LOOK and Sun™Graphical User Interface was developed by Sun Microsystems,Inc.for its users and licensees.Sun acknowledges the pioneering efforts of Xerox in researching and developing the concept of visual or graphical user interfaces for the computer industry.Sun holds a non-exclusive license from Xerox to the Xerox Graphical User Interface,which license also covers Sun’s licensees who implement OPEN LOOK GUIs and otherwise comply with Sun’s written license agreements.ernment Rights–Commercial ernment users are subject to the Sun Microsystems,Inc.standard license agreement and applicable provisions of the FAR and its supplements.DOCUMENTATION IS PROVIDED“AS IS”AND ALL EXPRESS OR IMPLIED CONDITIONS,REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT,ARE DISCLAIMED,EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD TO BE LEGALLY INVALID.Copyright2005Sun Microsystems,Inc.4150Network Circle,Santa Clara,CA95054U.S.A.Tous droits réservés.Ce produit ou document est protégépar un copyright et distribuéavec des licences qui en restreignent l’utilisation,la copie,la distribution,et ladécompilation.Aucune partie de ce produit ou document ne peutêtre reproduite sous aucune forme,par quelque moyen que ce soit,sansl’autorisation préalable etécrite de Sun et de ses bailleurs de licence,s’il y en a.Le logiciel détenu par des tiers,et qui comprend la technologie relative aux polices de caractères,est protégépar un copyright et licenciépar des fournisseurs de Sun.Des parties de ce produit pourrontêtre dérivées du système Berkeley BSD licenciés par l’Universitéde Californie.UNIX est une marque déposée aux Etats-Unis et dans d’autres pays et licenciée exclusivement par X/Open Company,Ltd.Sun,Sun Microsystems,le logo Sun,,AnswerBook,AnswerBook2,et Solaris sont des marques de fabrique ou des marques déposées,de Sun Microsystems,Inc.aux Etats-Unis et dans d’autres pays.L’interface d’utilisation graphique OPEN LOOK et Sun™aétédéveloppée par Sun Microsystems,Inc.pour ses utilisateurs et licenciés.Sun reconnaît les efforts de pionniers de Xerox pour la recherche et le développement du concept des interfaces d’utilisation visuelle ou graphique pour l’industrie de l’informatique.Sun détient une licence non exclusive de Xerox sur l’interface d’utilisation graphique Xerox,cette licence couvrantégalement les licenciés de Sun qui mettent en place l’interface d’utilisation graphique OPEN LOOK et qui en outre se conforment aux licencesécrites de Sun. CETTE PUBLICATION EST FOURNIE“EN L’ETAT”ET AUCUNE GARANTIE,EXPRESSE OU IMPLICITE,N’EST ACCORDEE,Y COMPRIS DES GARANTIES CONCERNANT LA VALEUR MARCHANDE,L’APTITUDE DE LA PUBLICATION A REPONDRE A UNE UTILISATION PARTICULIERE,OU LE FAIT QU’ELLE NE SOIT PAS CONTREFAISANTE DE PRODUIT DE TIERS.CE DENI DE GARANTIE NES’APPLIQUERAIT PAS,DANS LA MESURE OU IL SERAIT TENU JURIDIQUEMENT NUL ET NON AVENU.040910@9495ContentsPreface71Overview of the Solaris x86Assembler11Assembler Overview11Syntax Differences Between x86Assemblers12Assembler Command Line122Solaris x86Assembly Language Syntax13Lexical Conventions13Statements13Tokens15Instructions,Operands,and Addressing17Instructions17Operands18Assembler Directives203Instruction Set Mapping25Instruction Overview25General-Purpose Instructions26Data Transfer Instructions26Binary Arithmetic Instructions30Decimal Arithmetic Instructions31Logical Instructions32Shift and Rotate Instructions32Bit and Byte Instructions333Control Transfer Instructions35String Instructions38I/O Instructions39Flag Control(EFLAG)Instructions40Segment Register Instructions41Miscellaneous Instructions41Floating-Point Instructions42Data Transfer Instructions(Floating Point)42Basic Arithmetic Instructions(Floating-Point)43Comparison Instructions(Floating-Point)45Transcendental Instructions(Floating-Point)46Load Constants(Floating-Point)Instructions47Control Instructions(Floating-Point)47SIMD State Management Instructions49MMX Instructions49Data Transfer Instructions(MMX)50Conversion Instructions(MMX)50Packed Arithmetic Instructions(MMX)51Comparison Instructions(MMX)52Logical Instructions(MMX)53Shift and Rotate Instructions(MMX)53State Management Instructions(MMX)54SSE Instructions54SIMD Single-Precision Floating-Point Instructions(SSE)55MXCSR State Management Instructions(SSE)6164–Bit SIMD Integer Instructions(SSE)61Miscellaneous Instructions(SSE)62SSE2Instructions63SSE2Packed and Scalar Double-Precision Floating-Point Instructions63SSE2Packed Single-Precision Floating-Point Instructions70SSE2128–Bit SIMD Integer Instructions70SSE2Miscellaneous Instructions72Operating System Support Instructions7364–Bit AMD Opteron Considerations75Index774x86Assembly Language Reference Manual•January2005TablesTABLE3–1Data Transfer Instructions26TABLE3–2Binary Arithmetic Instructions30TABLE3–3Decimal Arithmetic Instructions32TABLE3–4Logical Instructions32TABLE3–5Shift and Rotate Instructions33TABLE3–6Bit and Byte Instructions34TABLE3–7Control Transfer Instructions36TABLE3–8String Instructions38TABLE3–9I/O Instructions40TABLE3–10Flag Control Instructions40TABLE3–11Segment Register Instructions41TABLE3–12Miscellaneous Instructions42TABLE3–13Data Transfer Instructions(Floating-Point)42TABLE3–14Basic Arithmetic Instructions(Floating-Point)44TABLE3–15Comparison Instructions(Floating-Point)45TABLE3–16Transcendental Instructions(Floating-Point)46TABLE3–17Load Constants Instructions(Floating-Point)47TABLE3–18Control Instructions(Floating-Point)47TABLE3–19SIMD State Management Instructions49TABLE3–20Data Transfer Instructions(MMX)50TABLE3–21Conversion Instructions(MMX)50TABLE3–22Packed Arithmetic Instructions(MMX)51TABLE3–23Comparison Instructions(MMX)52TABLE3–24Logical Instructions(MMX)53TABLE3–25Shift and Rotate Instructions(MMX)53TABLE3–26State Management Instructions(MMX)54TABLE3–27Data Transfer Instructions(SSE)555TABLE3–28Packed Arithmetic Instructions(SSE)56TABLE3–29Comparison Instructions(SSE)58TABLE3–30Logical Instructions(SSE)59TABLE3–31Shuffle and Unpack Instructions(SSE)59TABLE3–32Conversion Instructions(SSE)60TABLE3–33MXCSR State Management Instructions(SSE)61TABLE3–3464–Bit SIMD Integer Instructions(SSE)61TABLE3–35Miscellaneous Instructions(SSE)62TABLE3–36SSE2Data Movement Instructions64TABLE3–37SSE2Packed Arithmetic Instructions65TABLE3–38SSE2Logical Instructions66TABLE3–39SSE2Compare Instructions67TABLE3–40SSE2Shuffle and Unpack Instructions67TABLE3–41SSE2Conversion Instructions68TABLE3–42SSE2Packed Single-Precision Floating-Point Instructions70TABLE3–43SSE2128–Bit SIMD Integer Instructions71TABLE3–44SSE2Miscellaneous Instructions72TABLE3–45Operating System Support Instructions736x86Assembly Language Reference Manual•January2005PrefaceThe x86Assembly Language Reference Manual documents the syntax of the Solaris™x86 assembly language.This manual is provided to help experienced programmers understand the assembly language output of Solaris compilers.This manual is neither an introductory book about assembly language programming nor a reference manual for the x86architecture.Note–In this document the term“x86”refers to64-bit and32-bit systems manufactured using processors compatible with the AMD64or Intel Xeon/Pentium product families.For supported systems,see the Solaris10Hardware Compatibility List.Who Should Use This BookThis manual is intended for experienced x86assembly language programmers who are familiar with the x86architecture.Before You Read This BookYou should have a thorough knowledge of assembly language programming in general and be familiar with the x86architecture in specific.You should be familiar with the ELF objectfile format.This manual assumes that you have the following documentation available for reference:I IA-32Intel Architecture Software Developer’s Manual(Intel Corporation,2004).Volume1:Basic Architecture.Volume2:Instruction Set Reference A-M.Volume3: Instruction Set Reference N-Z.Volume4:System Programming Guide.7I AMD64Architecture Programmer’s Manual(Advanced Micro Devices,2003).Volume1:Application Programming.Volume2:System Programming.Volume3:General-Purpose and System Instructions.Volume4:128-Bit Media Instructions.Volume5:64-Bit Media and x87Floating-Point Instructions.I Linker and Libraries GuideI Sun Studio9:C User’s GuideI Sun Studio9:Fortran User’s Guide and Fortran Programming GuideI Man pages for the as(1),ld(1),and dis(1)utilities.How This Book Is OrganizedChapter1provides an overview of the x86functionality supported by the Solaris x86assembler.Chapter2documents the syntax of the Solaris x86assembly language.Chapter3maps Solaris x86assembly language instruction mnemonics to the nativex86instruction set.Accessing Sun Documentation OnlineThe SM Web site enables you to access Sun technical documentationonline.You can browse the archive or search for a specific book title orsubject.The URL is .Ordering Sun DocumentationSun Microsystems offers select product documentation in print.For a list ofdocuments and how to order them,see“Buy printed documentation”at.8x86Assembly Language Reference Manual•January2005Typographic ConventionsThe following table describes the typographic changes that are used in this book. TABLE P–1Typographic ConventionsTypeface or Symbol Meaning ExampleAaBbCc123The names of commands,files,anddirectories,and onscreen computeroutput Edit your.loginfile.Use ls-a to list allfiles. machine_name%you have mail.AaBbCc123What you type,contrasted with onscreencomputer output machine_name%su Password:AaBbCc123Command-line placeholder:replace witha real name or value The command to remove afile is rmfilename.AaBbCc123Book titles,new terms,and terms to beemphasized Read Chapter6in the User’s Guide.Perform a patch analysis.Do not save thefile.[Note that some emphasized items appear bold online.]Shell Prompts in Command ExamplesThe following table shows the default system prompt and superuser prompt for theC shell,Bourne shell,and Korn shell.TABLE P–2Shell PromptsShell PromptC shell prompt machine_name%C shell superuser prompt machine_name#Bourne shell and Korn shell prompt$9TABLE P–2Shell Prompts(Continued)Shell PromptBourne shell and Korn shell superuser prompt#10x86Assembly Language Reference Manual•January2005CHAPTER1Overview of the Solaris x86AssemblerThis chapter provides a brief overview of the Solaris x86assembler as.This chapterdiscusses the following topics:I“Assembler Overview”on page11I“Syntax Differences Between x86Assemblers”on page12I“Assembler Command Line”on page12Assembler OverviewThe Solaris x86assembler as translates Solaris x86assembly language into Executableand Linking Format(ELF)relocatable objectfiles that can be linked with other objectfiles to create an executablefile or a shared objectfile.(See Chapter7,“Object FileFormat,”in Linker and Libraries Guide,for a complete discussion of ELF objectfileformat.)The assembler supports macro processing by the C preprocessor(cpp)or them4macro processor.The assembler supports the instruction sets of the followingCPUs:Intel8086/8088processorsIntel286processorIntel386processorIntel486processorIntel Pentium processorIntel Pentium Pro processorIntel Pentium II processorPentium II Xeon processorIntel Celeron processorIntel Pentium III processorPentium III Xeon processorAdvanced Micro Devices Athlon processor11Advanced Micro Devices Opteron processorSyntax Differences Between x86AssemblersThere is no standard assembly language for the x86architecture.Vendorimplementations of assemblers for the x86architecture instruction sets differ in syntaxand functionality.The syntax of the Solaris x86assembler is compatible with thesyntax of the assembler distributed with earlier releases of the UNIX operating system(this syntax is sometimes termed“AT&T syntax”).Developers familiar with otherassemblers derived from the original UNIX assemblers,such as the Free SoftwareFoundation’s gas,willfind the syntax of the Solaris x86assembler verystraightforward.However,the syntax of x86assemblers distributed by Intel and Microsoft(sometimestermed“Intel syntax”)differs significantly from the syntax of the Solaris x86assembler.These differences are most pronounced in the handling of instructionoperands:I The Solaris and Intel assemblers use the opposite order for source and destinationoperands.I The Solaris assembler specifies the size of memory operands by adding a suffix tothe instruction mnemonic,while the Intel assembler prefixes the memoryoperands.I The Solaris assembler prefixes immediate operands with a dollar sign($)(ASCII0x24),while the Intel assembler does not delimit immediate operands.See Chapter2for additional differences between x86assemblers.Assembler Command LineDuring the translation of higher-level languages such as C and Fortran,the compilersmight invoke as using the alias fbe(“Fortran back end”).You can invoke theassembler manually from the shell command line with either name,as or fbe.See theas(1)man page for the definitive discussion of command syntax and command lineoptions.12x86Assembly Language Reference Manual•January2005CHAPTER2Solaris x86Assembly Language SyntaxThis chapter documents the syntax of the Solaris x86assembly language.I“Lexical Conventions”on page13I“Instructions,Operands,and Addressing”on page17I“Assembler Directives”on page20Lexical ConventionsThis section discusses the lexical conventions of the Solaris x86assembly language.StatementsAn x86assembly language program consists of one or morefiles containing statements.A statement consists of tokens separated by whitespace and terminated by either anewline character(ASCII0x0A)or a semicolon(;)(ASCII0x3B).Whitespace consists ofspaces(ASCII0x20),tabs(ASCII0x09),and formfeeds(ASCII0x0B)that are notcontained in a string or comment.More than one statement can be placed on a singleinput line provided that each statement is terminated by a semicolon.A statement canconsist of a comment.Empty statements,consisting only of whitespace,are allowed.CommentsA comment can be appended to a statement.The comment consists of the slashcharacter(/)(ASCII0x2F)followed by the text of the comment.The comment isterminated by the newline that terminates the statement.13LabelsA label can be placed at the beginning of a statement.During assembly,the label isassigned the current value of the active location counter and serves as an instructionoperand.There are two types of lables:symbolic and numeric.Symbolic LabelsA symbolic label consists of an identifier(or symbol)followed by a colon(:)(ASCII0x3A).Symbolic labels must be defined only once.Symbolic labels have global scopeand appear in the objectfile’s symbol table.Symbolic labels with identifiers beginning with a period(.)(ASCII0x2E)areconsidered to have local scope and are not included in the objectfile’s symbol table.Numeric LabelsA numeric label consists of a single digit in the range zero(0)through nine(9)followedby a colon(:).Numeric labels are used only for local reference and are not included inthe objectfile’s symbol table.Numeric labels have limited scope and can be redefinedrepeatedly.When a numeric label is used as a reference(as an instruction operand,for example),the suffixes b(“backward”)or f(“forward”)should be added to the numeric label.Fornumeric label N,the reference N b refers to the nearest label N defined before thereference,and the reference N f refers to the nearest label N defined after the reference.The following example illustrates the use of numeric labels:1:/define numeric label"1"one:/define symbolic label"one"/...assembler code...jmp1f/jump to first numeric label"1"defined/after this instruction/(this reference is equivalent to label"two")jmp1b/jump to last numeric label"1"defined/before this instruction/(this reference is equivalent to label"one")1:/redefine label"1"two:/define symbolic label"two"jmp1b/jump to last numeric label"1"defined/before this instruction/(this reference is equivalent to label"two")14x86Assembly Language Reference Manual•January2005TokensThere arefive classes of tokens:I Identifiers(symbols)I KeywordsI Numerical constantsI String ConstantsI OperatorsIdentifiersAn identifier is an arbitrarily-long sequence of letters and digits.Thefirst character must be a letter;the underscore(_)(ASCII0x5F)and the period(.)(ASCII0x2E)are considered to be letters.Case is significant:uppercase and lowercase letters are different.KeywordsKeywords such as x86instruction mnemonics(“opcodes”)and assembler directives are reserved for the assembler and should not be used as identifiers.See Chapter3for a list of the Solaris x86mnemonics.See“Assembler Directives”on page20for the list of as assembler directives.Numerical ConstantsNumbers in the x86architecture can be integers orfloating point.Integers can be signed or unsigned,with signed integers represented in two’s complement representation. Floating-point numbers can be:single-precisionfloating-point;double-precisionfloating-point;and double-extended precisionfloating-point.Integer ConstantsIntegers can be expressed in several bases:I Decimal.Decimal integers begin with a non-zero digit followed by zero or moredecimal digits(0–9).I Binary.Binary integers begin with“0b”or“0B”followed by zero or more binarydigits(0,1).I Octal.Octal integers begin with zero(0)followed by zero or more octal digits(0–7).I Hexadecimal.Hexadecimal integers begin with“0x”or“0X”followed by one ormore hexadecimal digits(0–9,A–F).Hexadecimal digits can be either uppercase or lowercase.Chapter2•Solaris x86Assembly Language Syntax15Floating Point ConstantsFloating point constants have the following format:I Sign(optional)–either plus(+)or minus(–)I Integer(optional)–zero or more decimal digits(0–9)I Fraction(optional)–decimal point(.)followed by zero or more decimal digitsI Exponent(optional)–the letter“e”or“E”,followed by an optional sign(plus orminus),followed by one or more decimal digits(0–9)A validfloating point constant must have either an integer part or a fractional part.String ConstantsA string constant consists of a sequence of characters enclosed in double quotes(")(ASCII0x22).To include a double-quote character("),single-quote character(’),orbackslash character(\)within a string,precede the character with a backslash(\)(ASCII0x5C).A character can be expressed in a string as its ASCII value in octalpreceded by a backslash(for example,the letter“J”could be expressed as“\112”).Theassembler accepts the following escape sequences in strings:Escape Sequence Character Name ASCII Value(hex)\n newline0A\r carriage return0D\b backspace08\t horizontal tab09\f form feed0C\v vertical tab0BOperatorsThe assembler supports the following operators for use in expressions.Operators haveno assigned precedence.Expressions can be grouped in square brackets([])toestablish precedence.+Addition-Subtraction\*Multiplication\/Division&Bitwise logical AND16x86Assembly Language Reference Manual•January2005|Bitwise logical OR>>Shift right<<Shift left\%Remainder!Bitwise logical AND NOT^Bitwise logical XORNote–The asterisk(*),slash(/),and percent sign(%)characters are overloaded.When used as operators in an expression,these characters must be preceded by the backslash character(\).Instructions,Operands,and Addressing Instructions are operations performed by the CPU.Operands are entities operated upon by the instruction.Addresses are the locations in memory of specified data.InstructionsAn instruction is a statement that is executed at runtime.An x86instruction statement can consist of four parts:I Label(optional)I Instruction(required)I Operands(instruction specific)I Comment(optional)See“Statements”on page13for the description of labels and comments.The terms instruction and mnemonic are used interchangeably in this document to refer to the names of x86instructions.Although the term opcode is sometimes used as a synonym for instruction,this document reserves the term opcode for the hexadecimal representation of the instruction value.Chapter2•Solaris x86Assembly Language Syntax17For most instructions,the Solaris x86assembler mnemonics are the same as the Intelor AMD mnemonics.However,the Solaris x86mnemonics might appear to bedifferent because the Solaris mnemonics are suffixed with a one-character modifier thatspecifies the size of the instruction operands.That is,the Solaris assembler derives itsoperand type information from the instruction name and the suffix.If a mnemonic isspecified with no type suffix,the operand type defaults to long.Possible operandtypes and their instruction suffixes are:b Byte(8–bit)w Word(16–bit)l Long(32–bit)(default)q Quadword(64–bit)The assembler recognizes the following suffixes for x87floating-point instructions:[no suffix]Instruction operands are registers onlyl(“long”)Instruction operands are64–bits(“short”)Instruction operands are32–bitSee Chapter3for a mapping between Solaris x86assembly language mnemonics andthe equivalent Intel or AMD mnemonics.OperandsAn x86instruction can have zero to three operands.Operands are separated bycommas(,)(ASCII0x2C).For instructions with two operands,thefirst(lefthand)operand is the source operand,and the second(righthand)operand is the destinationoperand(that is,source→destination).Note–The Intel assembler uses the opposite order(destination←source)for operands.Operands can be immediate(that is,constant expressions that evaluate to an inlinevalue),register(a value in the processor number registers),or memory(a value stored inmemory).An indirect operand contains the address of the actual operand value.Indirect operands are specified by prefixing the operand with an asterisk(*)(ASCII0x2A).Only jump and call instructions can use indirect operands.I Immediate operands are prefixed with a dollar sign($)(ASCII0x24)I Register names are prefixed with a percent sign(%)(ASCII0x25)18x86Assembly Language Reference Manual•January2005I Memory operands are specified either by the name of a variable or by a register thatcontains the address of a variable.A variable name implies the address of avariable and instructs the computer to reference the contents of memory at that address.Memory references have the following syntax:segment:offset(base,index,scale).I Segment is any of the x86architecture segment registers.Segment is optional:ifspecified,it must be separated from offset by a colon(:).If segment is omitted,the value of%ds(the default segment register)is assumed.I Offset is the displacement from segment of the desired memory value.Offset isoptional.I Base and index can be any of the general32–bit number registers.I Scale is a factor by which index is to be multipled before being added to base tospecify the address of the operand.Scale can have the value of1,2,4,or8.Ifscale is not specified,the default value is1.Some examples of memory addresses are:movl var,%eaxMove the contents of memory location var into number register%eax.movl%cs:var,%eaxMove the contents of memory location var in the code segment(register%cs)into number register%eax.movl$var,%eaxMove the address of var into number register%eax.movl array_base(%esi),%eaxAdd the address of memory location array_base to the contents of numberregister%esi to determine an address in memory.Move the contents of thisaddress into number register%eax.movl(%ebx,%esi,4),%eaxMultiply the contents of number register%esi by4and add the result to thecontents of number register%ebx to produce a memory reference.Move thecontents of this memory location into number register%eax.movl struct_base(%ebx,%esi,4),%eaxMultiply the contents of number register%esi by4,add the result to thecontents of number register%ebx,and add the result to the address ofstruct_base to produce an address.Move the contents of this address intonumber register%eax.Chapter2•Solaris x86Assembly Language Syntax19Assembler DirectivesDirectives are commands that are part of the assembler syntax but are not related to thex86processor instruction set.All assembler directives begin with a period(.)(ASCII0x2E)..align integer,padThe.align directive causes the next data generated to be aligned modulo integerbytes.Integer must be a positive integer expression and must be a power of2.Ifspecified,pad is an integer bye value used for padding.The default value of pad forthe text section is0x90(nop);for other sections,the default value of pad is zero(0)..ascii"string"The.ascii directive places the characters in string into the object module at thecurrent location but does not terminate the string with a null byte(\0).String mustbe enclosed in double quotes(")(ASCII0x22).The.ascii directive is not valid forthe.bss section..bcd integerThe.bcd directive generates a packed decimal(80-bit)value into the currentsection.The.bcd directive is not valid for the.bss section..bssThe.bss directive changes the current section to.bss..bss symbol,integerDefine symbol in the.bss section and add integer bytes to the value of the locationcounter for.bss.When issued with arguments,the.bss directive does notchange the current section to.bss.Integer must be positive..byte byte1,byte2,...,byteNThe.byte directive generates initialized bytes into the current section.The.bytedirective is not valid for the.bss section.Each byte must be an8-bit value..2byte expression1,expression2,...,expressionNRefer to the description of the.value directive..4byte expression1,expression2,...,expressionNRefer to the description of the.long directive..8byte expression1,expression2,...,expressionNRefer to the description of the.quad directive..comm name,size,alignmentm directive allocates storage in the data section.The storage is referencedby the identifier name.Size is measured in bytes and must be a positive integer.Name cannot be predefined.Alignment is optional.If alignment is specified,theaddress of name is aligned to a multiple of alignment..dataThe.data directive changes the current section to.data.20x86Assembly Language Reference Manual•January2005。

Assembly汇编语言基础入门汇编语言是一种低级机器语言的表示形式，它使用助记符和符号来代替机器码，方便程序员编写和理解。

在计算机科学领域，汇编语言是一门重要的编程语言，对于理解计算机的工作原理和进行底层的编程调优具有重要作用。

本文将介绍汇编语言的基础知识，包括语法和常用指令的使用。

一、汇编语言概述汇编语言是计算机硬件指令集的一种表示形式，它通过助记符和符号来代表不同的机器指令。

汇编语言与具体的计算机体系结构紧密相关，不同的计算机体系结构使用不同的汇编语言。

汇编语言的优点是直接操作硬件，可以实现高度优化的代码，但是缺点是可移植性差，需要了解底层的硬件细节。

汇编语言通常用于编写驱动程序、操作系统和高性能的应用程序。

二、汇编语言的基本语法1. 汇编语言使用英文助记符作为指令的代号，例如MOV表示数据传送指令，ADD表示加法指令。

2. 汇编语言使用伪指令来定义常量、变量和符号地址，例如DAT 定义数据，ORG定义起始地址。

3. 汇编语言使用标号来表示程序的入口和跳转地址，标号可以是任意合法的字符串。

4. 汇编语言使用寄存器来操作数据，不同的寄存器有不同的用途，例如AX用于存放常用的数据，BX用于存放地址。

5. 汇编语言使用操作数来指定操作的数据，操作数可以是寄存器、内存或立即数。

三、汇编语言的常用指令1. 数据传送指令：MOV指令用于将数据从一个位置拷贝到另一个位置。

2. 算术指令：ADD、SUB、MUL、DIV等指令用于进行基本的算术运算。

3. 逻辑指令：AND、OR、NOT、XOR等指令用于进行逻辑运算。

4. 分支指令：JMP、JE、JNE、JZ、JNZ等指令用于程序的跳转和条件判断。

5. 栈指令：PUSH、POP、CALL、RET等指令用于操作程序的栈空间。

6. 输入输出指令：IN、OUT、INT等指令用于与外部设备进行数据交换。

四、编写汇编程序的步骤编写汇编程序可以分为以下几个步骤：1. 确定程序的功能和需求。

Rules Definition Required AdvisoryTotal Implemented byLDRA 10317120Partially implemented byLDRA 617Not deemed to be statically analysable by atool12214NOTE: Of the 14 rules deemed 'Not statically analysable", a number of them are checkable to some extent with facilities available in the LDRA tool suite. This may be through the application of a related programming standard, or some other technique such as dynamic analysis.Total12120141This information has been compiled using version 7.7.1 of the LDRA tool suite and is correct as of July 2008.MISRA-C:2004 Coding StandardThe LDRA tool suite is developed and certified to BS EN ISO 9001:2000. This comparison has used the revised MISRA standard, MISRA-C:2004 "Guidelines for the use of the C language in critical systems" was published in October 2004.LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description1.1Required293 S All code shall conform to ISO 9899:1990“Programming languages – C”, amended andcorrected by ISO/IEC 9899/COR1:1995, ISO/IEC 9899/AMD1:1995, and ISO/IEC 9899/COR2:1996.Non Ansi construct used.1.2Required412 SNo reliance shall be placed on undefined orunspecified behaviour.Undefined behaviour, \ before E-O-F.1.3Required N/AMultiple compilers and/or languages shall only be used if there is a common defined interfacestandard for object code to which thelanguages/compilers/assemblers conform.N/A1.4, 5.1Required 17 D The compiler/linker shall be checked to ensurethat 31 character significance and case sensitivityare supported for external identifiers.Identifier not unique within 31 characters. 1.5Advisory N/AFloating-point implementations should complywith a defined floating-point standard.N/A2.1Required 88 SAssembly language shall be encapsulated andisolated.Procedure is not pure assembler. 2.2Required 110 SSource code shall only use /* … */ stylecomments.Use of single line comment(s) //. 2.3Required 119 SThe character sequence /* shall not be usedwithin a comment.Nested comment found2.4Advisory 302 S Sections of code should not be “commented out”. Comment possibly contains code3.1Required N/AAll usage of implementation-defined behaviour shall be documented.N/A 3.2Required N/AThe character set and the correspondingencoding shall be documented.N/A3.3Advisory 373 S The implementation of integer division in thechosen compiler should be determined,documented and taken into account.Use of integer division 3.4Required69 SAll uses of the #pragma directive shall bedocumented and explained.#pragma used.LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / Advisory LDRA Rule Number MISRA Description LDRA Rule Description316 SBit field is not unsigned integral. 328 S Non bit field member in bitfield struct. 42 S Use of bit field in structure declaration. 226 SBit field is not octal, hex or suffix u;3.6RequiredN/A All libraries used in production code shall be written to comply with the provisions of thisdocument, and shall have been subject to appropriate validation.N/A4.1, 7.1Required 176 S Only those escape sequences that are defined inthe ISO C standard shall be used.Non standard escape sequence in source.4.2Required 81 S Trigraphs shall not be used.Use of trigraphs.384 S Identifier matches macro name in 31 chars.61 X Identifier match in *** chars. 5.2 - 5.5Required 131 S Identifiers in an inner scope shall not use thesame name as an identifier in an outer scope,and therefore hide that identifier.Name reused in inner scope. 5.3, 5.6Required 112 STypedef name redeclared. 374 S Name conflict with typedef 16 X - 24 XIdentifier resuse: typedef vs …325 SInconsistent use of tag.4 X - 15 XIdentifier resuse: tag vs …18 D Identifier name reused 25 X - 39 XIdentifier reuse: ...91 S Name redeclared in another namespace (MR).40 X - 48 X Identifier reuse: ...5.6, 5.7Advisory383 S Identifier name matches macro name.Identifiers (internal and external) shall not rely on the significance of more than 31 characters.Required5.1Required 5.3 A tag name shall be a unique identifier.No identifier in one name space should have the same spelling as an identifier in another namespace, with the exception of structure and unionmember names.Advisory 5.63.5RequiredRequired 5.4Advisory 5.5If it is being relied upon, the implementationdefined behaviour and packing of bitfields shallbe documented.A typedef name shall be a unique identifier.No object or function identifier with static storageduration should be reused.LDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description327 SReuse of struct member name. 49 X - 60 XIdentifier reuse: ...6.1Required 329 SThe plain char type shall be used only for thestorage and use of character values.Operation not appropriate to plain char. 93 S Value is not of appropriate type. 96 S Use of mixed mode arithmetic. 90 S Basic type declaration used. 495 S Typedef has no size indication6.4Required 73 SBit fields shall only be defined to be of typeunsigned int or signed int.Bit field not signed or unsigned int.6.5Required 72 S Bit fields of type signed int shall be at least 2 bitslong.Signed bit field less than 2 bits wide.7.1Required83 S Octal constants (other than zero) and octalescape sequences shall not be used.Octal number found.24 DProcedure definition has no associated prototype 8.2Required326 SWhenever an object or function is declared ordefined, its type shall be explicitly stated.Declaration is missing type.102 SFunction and prototype return inconsistent 103 SFunction and prototype param inconsistent 62 XFunction prototype/defn return type mismatch.63 XFunction prototype/defn parameter type mismatch.1 X Declaration types do not match across a system.360 S Incompatible type8.3RequiredFunction call with no prior declaration 496 S8.1Required8.4Required6.2, 12.1, 12.6RequiredAdvisory 6.35.7Advisory Functions shall have prototype declarations and the prototype shall be visible at both the function definition and call.If objects or functions are declared more than once their types shall be compatible.Signed and unsigned char type shall be used only for the storage and use of numeric values.Typedefs that indicate size and signedness should be used in place of the basic types.No identifier name should be reused.For each function parameter the type given in the declaration and definition shall be identical, and the return types shall also be identical.LDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description286 S Functions defined in header file. 287 SVariable definitions in header file. 8.6Required 296 S Functions shall be declared at file scope.Function declared at block scope. 8.7Required 25 DObjects shall be defined at block scope if theyare only accessed from within a single function.Scope of variable could be reduced26 D Variable should be defined once in only one file 60 DExternal object should be declared only once.172 S Variable declared multiply. 33 DNo real declaration for external variable.27 D Variable should be declared static61 D Procedure should be declared static 461 SIdentifier with ambiguous linkage.27 D Variable should be declared static 61 DProcedure should be declared static 8.12Required 127 S When an array is declared with external linkage,its size shall be stated explicitly or defined implicitly by initialisation.Array has no bounds specified.9.1Required 5 D All automatic variables shall have been assigneda value before being used.Procedure contains UR data flow anomalies.9.2Required105 S Braces shall be used to indicate and match thestructure in the non-zero initialisation of arrays and structures.Struct field initialisation brace fault.The static storage class specifier shall be used indefinitions and declarations of objects andfunctions that have internal linkage.RequiredAn external object or function shall be declared inone and only one file.Required 8.88.5Required There shall be no definitions of objects orfunctions in a header file.An identifier with external linkage shall haveexactly one external definition.Required 8.98.108.11RequiredAll declarations and definitions of objects or functions at file scope shall have internal linkage unless external linkage is required.LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description9.3Required85 S In an enumerator list, the “=” construct shall notbe used to explicitly initialise members other than the first, unless all items are explicitly initialised.Incomplete initialisation of enumerator.93 S Value is not of appropriate type. 96 SUse of mixed mode arithmetic. 433 SType conversion without cast.(a) 434 S Signed/unsigned conversion without cast.(a) 435 S Float/integer conversion without cast.(a) 446 S Narrower int conversion without cast.(a) 488 SValue outside range of underlying type.(b) 452 SNo cast for widening complex int expression.(c) 458 SImplicit conversion: actual to formal param.(c) 491 S No cast for widening int parameter.(d) 101 S Function return type inconsistent.(d) 457 SImplicit int widening for function return. 93 S Value is not of appropriate type. 96 S Use of mixed mode arithmetic. 433 S Type conversion without cast.(a) 435 S Float/integer conversion without cast. (a) 445 S Narrower float conversion without cast.(b) 451 SNo cast for widening complex float expression.(c) 458 SImplicit conversion: actual to formal param.(c) 490 S No cast for widening float parameter.(d) 101 S Function return type inconsistent.(d) 456 S Implicit float widening for function return.Required10.2The value of an expression of floating type shall not be implicitly converted to a different type if:a) it is not a conversion to a wider floating type, orb) the expression is complex, or c) the expression is a function argument, or d) the expression is a return expression10.1RequiredThe value of an expression of integer type shallnot be implicitly converted to a differentunderlying type if:a) it is not a conversion to a wider integer type of the same signedness, orb) the expression is complex, or c) the expression is not constant and is a function argument, ord) the expression is not constant and is a returnexpression LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / AdvisoryLDRA RuleNumberMISRA DescriptionLDRA Rule Description93 S Value is not of appropriate type. 433 S Type conversion without cast.332 S Widening cast on complex integer expression. 442 SSigned integral type cast to unsigned.443 S Unsigned integral type cast to signed.444 SIntegral type cast to non-integral.93 S Value is not of appropriate type. 433 SType conversion without cast.333 S Widening cast on complex float expression. 441 SFloat cast to non-float.10.5Required334 SIf the bitwise operators ~ and << are applied to an operand of underlying type unsigned char orunsigned short, the result shall be immediately cast to the underlying type of the operand. No cast when ~ or << applied to small types.10.6Required 331 SA “U” suffix shall be applied to all constants ofunsigned type.Literal value requires a U suffix. 11.1Required94 S & 95 S Conversions shall not be performed between apointer to a function and any type other than anintegral type.Conversions shall not be performed between a pointer to a function and any type other than an integral type.11.2Required94 SConversions shall not be performed between a pointer to object and any type other than anintegral type, another pointer to object type or a pointer to void.Casting operation on a pointer.439 SCast from pointer to integral type.440 SCast from integral type to pointer.11.4Advisory95 S A cast should not be performed between apointer to object type and a different pointer toobject type.Casting operation to a pointer.11.3AdvisoryA cast should not be performed between a pointer type and an integral type.10.4RequiredThe value of a complex expression of integer type may only be cast to a type that is narrowerand of the same signedness as the underlyingtype of the expression.Required10.3The value of a complex expression of floatingtype may only be cast to a narrower floating type.LDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule Number MISRA Description LDRA Rule Description203 SCast on a constant value.344 S Cast on volatile value. 96 SSee 6.2 above361 SExpression needs brackets.9 SAssignment operation in expression. 134 SVolatile variable in complex expression. 12.2, 12.3Required 35 D Expression has side effects.12.2, 12.4Required 1 Q Call has execution order dependant side effects.12.2, 12.13Required 30 S Deprecated usage of ++ or -- operators found.12.3Required54 SThe sizeof operator shall not be used on expressions that contain side effects.Sizeof operator with side effects.406 S Use of ++ or -- on RHS of && or || operator. 408 SVolatile variable accessed on RHS of && or ||.12.5Required49 SThe operands of a logical && or || shall beprimary-expressions. The oparands of a logical && or || shall be primary-expressions .12.6, 13.2Advisory 114 SThe operands of logical operators (&&, || and !) should be effectively Boolean. Expressions thatare effectively Boolean should not be used as operands to operators other than (&&, || and !).Expression is not Boolean.50 SUse of shift operator on signed type.Bitwise operators shall not be applied to operands whose underlying type is signed.12.4Required 12.7Required11.5Required12.1AdvisoryA cast shall not be performed that removes any const or volatile qualification from the typeaddressed by a pointer.Limited dependence should be placed on C’s operator precedence rules in expressions.The value of an expression shall be the sameunder any order of evaluation that the standardpermits.The right hand operand of a logical && or ||operator shall not contain side effects.12.2Required LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description120 S Use of bit operator on signed type. 12.8Required51 SThe right hand operand of a shift operator shall lie between zero and one less than the width inbits of the underlying type of the left hand operand.Shifting value too far.12.9Required 52 SThe unary minus operator shall not be applied toan expression whose underlying type is unsigned.Unsigned expression negated.12.10Required 53 S The comma operator shall not be e of comma operator. 493 S Numeric overflow.494 SNumeric underflow.12.12Required 345 S The underlying bit representations of floating-point values shall not be used.Bit operator with floating point operand.12.13Advisory 30 S The increment (++) and decrement (--) operatorsshould not be mixed with other operators in anexpression.See 12.213.1Required 132 S Assignment operators shall not be used inexpressions that yield a Boolean value.Assignment operator in boolean expression.13.2Advisory 114 S Tests of a value against zero should be madeexplicit, unless the operand is effectively Boolean.See 12.613.3Required 56 S Floating-point expressions shall not be tested forequality or inequality.Equality comparison of floating point.13.4Required39 SThe controlling expression of a for statementshall not contain any objects of floating type.Unsuitable type for loop variable.429 SEmpty middle expression in for loop. 430 SInconsistent usage of loop control variable. 270 S For loop initialisation is not simple. 271 SFor loop incrementation is not simple.12.11Advisory Evaluation of constant unsigned integer expressions should not lead to wrap-around.operands whose underlying type is signed.The three expressions of a for statement shall beconcerned only with loop control.13.512.7RequiredRequiredLDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description13.6Required 55 D Numeric variables being used within a for loop foriteration counting shall not be modified in thebody of the loop.Modification of loop counter in loop body. 139 S Construct leads to infeasible code. 140 SInfeasible loop condition found.14.1Required1 J There shall be no unreachable code.Unreachable Code found.14.2Required57 S All non-null statements shall either :a) have at least one side-effect howeverexecuted, orb) cause control flow to change.Statement with no side effect.14.3Required 58 SBefore preprocessing, a null statement shall only occur on a line by itself; it may be followed by a comment provided that the first character following the null statement is a white space character.Null statement found.14.4Required 13 S The goto statement shall not be used.goto detected. 14.5Required 32 S The continue statement shall not be used.Use of continue statement. 31 SUse of break statement in loop. 409 SMore than one break statement in loop. 14.7Required 7 CA function shall have a single point of exit at theend of the function.Procedure has more than one exit point. 11 SNo brackets to loop body. 428 S No {} for switch. 14.9Required12 SAn if (expression) construct shall be followed by a compound statement. The else keyword shall befollowed by either a compound statement, or another if statement.No brackets to then/else.The statement forming the body of a switch, while, do ... while or for statement shall be acompound statement.For any iteration statement there shall be at most one break statement used for loop termination.Boolean operations whose results are invariantshall not be permitted.14.8Required14.613.7Required RequiredLDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description59 S Else alternative missing in if.477 S Empty else clause following else if.60 SEmpty switch statement.385 S MISRA switch statement syntax violation.15.1, 15.5Required 245 S A switch label shall only be used when the mostclosely-enclosing compound statement is the body of a switch statement.Case statement in nested block.15.2Required62 S An unconditional break statement shall terminateevery non ﷓empty switch clause.Switch Case not terminated with break.48 SNo default case in switch statement.322 S Default is not last case of switch. 410 SSwitch empty default has no comment.15.4Required 121 SA switch expression shall not represent a valuethat is effectively e of boolean expression in switch. 61 S Switch contains default only. 245 SCase statement in nested block.16.1Required 41 SFunctions shall not be defined with a variablenumber of arguments.Ellipsis used in procedure parameter list. 1 U Inter-file recursion found. 6 DRecursion in procedure calls found. 16.3Required 37 SIdentifiers shall be given for all of the parametersin a function prototype declaration.Procedure Parameter has a type but no identifier. 16.4Required 36 DThe identifiers used in the declaration anddefinition of a function shall be identical.Prototype and Definition name mismatch. 16.5Required 63 SFunctions with no parameters shall be declaredwith parameter type void.Empty parameter list to procedure/function. 21 S Number of parameters does not match.Every switch statement shall have at least onecase clause.Functions shall not call themselves, either directlyor indirectly.The number of arguments passed to a functionshall match the number of parameters.All if … else if constructs shall be terminated with an else clause.N/A15.5Required 16.2Required 14.10Required15.3Required16.6Required15N/AThe final clause of a switch statement shall bethe default clause.LDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA RuleNumberMISRA DescriptionLDRA Rule Description98 SActual and formal parameters inconsistent (MR).59 DParameter should be declared const.62 DPointer parameter should be declared const.2 DFunction does not return a value on all paths.36 S Function has no return statement. 66 S Function with empty return expression.16.9Required 99 S A function identifier shall only be used with eithera preceding &, or with a parenthesised parameter list, which may be empty.Function use is not a call.16.10RequiredDataflow anomalies If a function returns error information, then thaterror information shall be tested.N/A87 S Use of pointer arithmetic. 436 S Declaration does not specify an array.17.2Required438 SPointer subtraction shall only be applied topointers that address elements of the same array.Pointer subtraction not addressing one array.17.3Required 437 S >, >=, <, <= shall not be applied to pointer types except where they point to the same array.< > <= >= used on different object pointers.17.4Required 87 SArray indexing shall be the only allowed form of pointer arithmetic.See 17.117.5Advisory80 SThe declaration of objects should contain nomore than 2 levels of pointer indirection.Pointer indirection exceeds 2 levels.17.6Required 71 S The address of an object with automatic storage shall not be assigned to another object that may persist after the first object has ceased to exist.Pointer assignment to wider scope.465 S Struct/union not completely specified.481 SArray with no bounds in struct.17.1, 17.4RequiredAll exit paths from a function with non-void return type shall have an explicit return statement withan expression.Pointer arithmetic shall only be applied topointers that address an array or array element.A pointer parameter in a function prototype should be declared as pointer to const if the All structure and union types shall be complete at the end of a translation unit.Required16.8Required18.1Advisory16.7LDRA Ltd. reserves the right to change anyMISRA-C:2004Rule Required / Advisory LDRA Rule Number MISRA DescriptionLDRA Rule Description482 S Incomplete structure referenced.497 S Type is incomplete in translation unit.18.2Required 480 SAn object shall not be assigned to an overlappingobject.memcpy params access same variable.18.3Required N/A An area of memory shall not be reused forunrelated purposes.N/A18.4Required74 S Unions shall not be used. Union declared.75 S Executable code before an included file. 78 S Macro parameter not in brackets.338 S#include preceded by non preproc directives.19.2Advisory 100 SNon-standard characters should not occur inheader file names in #include directives.#include filename is non conformant. 292 SNo space between #include and filename. 339 S #include directive with illegal items. 427 SFilename in #include not in < > or " ". 19.4Required79 SC macros shall only expand to a braced initialiser, a constant, a parenthesisedexpression, a type qualifier, a storage class specifier, or a do-while-zero construct.Macro contains unacceptable items67 S #Define used in a block. 426 S #undef used in a block.19.6Required 342 SExtra chars after preprocessor directive. 19.6, 20.0Required 68 S#undef used. 19.7Advisory 340 SA function should be used in preference to afunction-like macro.Use of function like macro. 19.8Required 324 SA function-like macro shall not be invoked withoutall of its arguments.Macro call has wrong number of parameters. 19.9Required341 S Arguments to a function-like macro shall notcontain tokens that look like preprocessingdirectives.Preprocessor construct as macro parameter.Macros shall not be #define’d or #undef’d within ablock.#undef shall not be used.#include statements in a file should only bepreceded by other preprocessor directives orcomments.The #include directive shall be followed by eithera <filename> or "filename" sequence.the end of a translation unit.19.3Required19.5Required 19.1AdvisoryRequired18.1LDRA Ltd. reserves the right to change anyMISRA-C:2004RuleRequired / Advisory LDRA Rule NumberMISRA Description LDRA Rule Description19.10Required78 SIn the definition of a function-like macro each instance of a parameter shall be enclosed inparentheses unless it is used as the operand of # or ##.In the definition of a function-like macro the whole definition, and each instance of a parameter, shall be enclosed in parentheses or braces.19.11Required337 SAll macro identifiers in preprocessor directives shall be defined before use, except in #ifdef and#ifndef preprocessor directives and the defined() operator.Undefined macro variable in #if.19.12Required 76 SThere shall be at most one occurrence of the # or## operators in a single macro definition.More than one of # or ## in a macro. 19.13Advisory 125 S The # and ## operators should not be e of ## or # in a macro 335 S operator defined contains illegal items. 336 S#if expansion contains define operator.19.15Required243 S Precautions shall be taken in order to prevent thecontents of a header file being included twice.Included file not protected with #define.19.16Required147 S Preprocessing directives shall be syntacticallymeaningful even when excluded by thepreprocessor.Spurious characters after preprocessor directive126 S A #if has no #endif in the same file.343 S #else has no #if, etc in the same file. 86 S Attempt to define reserved word. 156 S Use of 'defined' keyword in macro body. 478 SMisra special prefix banned name.20.2Required 218 SThe names of standard library macros, objectsand functions shall not be is used in standard libraries. 20.3RequiredUnit TestingThe validity of values passed to library functions shall be checked.TBrun may be used to perform the necessary checks.Reserved identifiers, macros and functions in thestandard library, shall not be defined, redefinedor undefined.The defined preprocessor operator shall only beused in one of the two standard forms.All #else, #elif and #endif preprocessor directivesshall reside in the same file as the #if or #ifdef directive to which they are related.19.17Required19.14RequiredRequired20.1LDRA Ltd. reserves the right to change any。