Red Hat ENTERPRISE LINUX 4 - USING AS Using Manual

Also see for ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE: Installation guide Installation guide Tuning guide Installation guide Manual

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26 Chapter 4. SyntaxAnything from the line comment character to the next newline is considered a comment and is ignored.The line comment character is ; for the AMD 29K family; ; on the ARC; @ on the ARM; ; for theH8/300 family; ! for the H8/500 family; ; for the HPPA; # on the i386 and x86-64; # on the i960;; for the PDP-11; ; for picoJava; # for Motorola PowerPC; ! for the Renesas / SuperH SH; ! onthe SPARC; # on the ip2k; # on the m32r; | on the 680x0; # on the 68HC11 and 68HC12; ; on theM880x0; # on the Vax; ! for the Z8000; # on the V850; # for Xtensa systems; see Chapter 9 MachineDependent Features.On some machines there are two different line comment characters. One character only begins acomment if it is the first non-whitespace character on a line, while the other always begins a comment.The V850 assembler also supports a double dash as starting a comment that extends to the end of theline.-;To be compatible with past assemblers, lines that begin with # have a special interpretation. Followingthe # should be an absolute expression (Chapter 7 Expressions): the logical line number of the nextline. Then a string (Section 4.6.1.1 Strings) is allowed: if present it is a new logical file name. The restof the line, if any, should be whitespace.If the first non-whitespace characters on the line are not numeric, the line is ignored. (Just like acomment.)# This is an ordinary comment.# 42-6 "new_file_name" # New logical file name# This is logical line # 36.This feature is deprecated, and may disappear from future versions of as.4.4. SymbolsA symbol is one or more characters chosen from the set of all letters (both upper and lower case), digitsand the three characters _.$. On most machines, you can also use $ in symbol names; exceptionsare noted in Chapter 9 Machine Dependent Features. No symbol may begin with a digit. Case issignificant. There is no length limit: all characters are significant. Symbols are delimited by charactersnot in that set, or by the beginning of a file (since the source program must end with a newline, theend of a file is not a possible symbol delimiter). Chapter 6 Symbols.4.5. StatementsA statement ends at a newline character (\n) or line separator character. (The line separator is usually;, unless this conflicts with the comment character; Chapter 9 Machine Dependent Features.) Thenewline or separator character is considered part of the preceding statement. Newlines and separatorswithin character constants are an exception: they do not end statements.It is an error to end any statement with end-of-file: the last character of any input file should be anewline.An empty statement is allowed, and may include whitespace. It is ignored.A statement begins with zero or more labels, optionally followed by a key symbol which determineswhat kind of statement it is. The key symbol determines the syntax of the rest of the statement.If the symbol begins with a dot . then the statement is an assembler directive: typically valid forany computer. If the symbol begins with a letter the statement is an assembly language instruction:it assembles into a machine language instruction. Different versions of as for different computersrecognize different instructions. In fact, the same symbol may represent a different instruction in adifferent computer’s assembly language.