Provided by: nasm_0.99.06-2_i386 bug


       nasm - the Netwide Assembler, a portable 80x86 assembler


       nasm  [ -@ response file ] [ -f format ] [ -o outfile ] [ -l listfile ]
       [ options...  ] filename
       nasm -h
       nasm -v


       The nasm command assembles the file filename and directs output to  the
       file  outfile  if  specified.  If  outfile  is not specified, nasm will
       derive a default output file name from the  name  of  its  input  file,
       usually  by appending ‘.o’ or ‘.obj’, or by removing all extensions for
       a raw  binary  file.  Failing  that,  the  output  file  name  will  be

       -@ filename
              Causes  nasm  to  process  options from filename as if they were
              included on the command line.

       -a     Causes nasm to assemble  the  given  input  file  without  first
              applying the macro preprocessor.

       -D macro[=value]
              Pre-defines a single-line macro.

       -d macro[=value]
              Same as the -D option.

       -e     Causes  nasm  to  preprocess the given input file, and write the
              output to stdout (or the specified output file  name),  and  not
              actually assemble anything.

       -f format
              Specifies  the output file format. To see a list of valid output
              formats, use the -hf option.

       -g     Causes nasm to generate debug information in selected format

       -h     Causes nasm to exit immediately, after giving a summary  of  its
              invocation options.

       -hf    Same as -h , but also lists all valid output formats.

       -I directory
              Adds  a  directory  to  the  search  path for include files. The
              directory specification must include the trailing slash,  as  it
              will be directly prepended to the name of the include file.

       -i directory
              Same as the -I option.

       -l listfile
              Causes  an assembly listing to be directed to the given file, in
              which the original source is displayed on the  right  hand  side
              (plus the source for included files and the expansions of multi-
              line macros) and the generated code is shown in hex on the left.

       -M     Causes  nasm  to  output  Makefile-style dependencies to stdout;
              normal output is suppressed.

       -O number
              optimize branch offsets (-O0 disables, default).

       -o outfile
              Specifies a precise name for the output file, overriding  nasm’s
              default means of determining it.

       -P file
              Specifies a file to be pre-included, before the main source file
              starts to be processed.

       -p file
              Same as the -P option.

       -r     Causes nasm to exit immediately, after  displaying  its  version
              number.  (obsolete)

       -s     Causes  nasm  to  send  its  error  messages and/or help text to
              stdout instead of stderr.

       -t     Causes nasm to assemble in SciTech TASM compatible mode

       -U macro
              Undefines a single-line macro.

       -u macro
              Same as the -U option.

       -v     Causes nasm to exit immediately, after  displaying  its  version

              Causes  nasm  to  enable  or  disable certain classes of warning
              messages, for example -w+orphan-labels or -w-macro-params

       -X format
              specifies error reporting format (gnu or vc).

       -Z filename
              Causes nasm to redirect error messages to filename.  This option
              exists  to  support  operating  systems  on  which stderr is not
              easily redirected.

       This man page does not fully describe the  syntax  of  nasm’s  assembly
       language,  but  does  give  a  summary  of  the  differences from other

       Registers have no leading ‘%’  sign,  unlike  gas,  and  floating-point
       stack registers are referred to as st0, st1, and so on.

       Floating-point  instructions  may use either the single-operand form or
       the double. A TO keyword is provided; thus, one could either write

                      fadd st0,st1
                      fadd st1,st0

       or one could use the alternative single-operand forms

                      fadd st1
                      fadd to st1

       Uninitialised storage is reserved using the  RESB,  RESW,  RESD,  RESQ,
       REST and RESO pseudo-opcodes, each taking one parameter which gives the
       number of bytes, words, doublewords, quadwords  or  ten-byte  words  to

       Repetition  of data items is not done by the DUP keyword as seen in DOS
       assemblers, but by the use of the TIMES prefix, like this:

             message: times 3 db ’abc’
                      times 64-$+message db 0

       which defines the string ‘abcabcabc’, followed by the right  number  of
       zero bytes to make the total length up to 64 bytes.

       Symbol  references  are  always  understood  to  be immediate (i.e. the
       address of the symbol), unless square brackets are used, in which  case
       the contents of the memory location are used. Thus:

                      mov ax,wordvar

       loads AX with the address of the variable ‘wordvar’, whereas

                      mov ax,[wordvar]
                      mov ax,[wordvar+1]
                      mov ax,[es:wordvar+bx]

       all refer to the contents of memory locations. The syntaxes

                      mov ax,es:wordvar[bx]
                      es mov ax,wordvar[1]

       are not legal at all, although the use of a segment register name as an
       instruction prefix is valid, and can be used with instructions such  as
       LODSB which can’t be overridden any other way.

       Constants may be expressed numerically in most formats: a trailing H, Q
       or B denotes hex, octal or binary respectively, and a leading  ‘0x’  or
       ‘$’  denotes  hex  as  well. Leading zeros are not treated specially at
       all.  Character constants may be enclosed in single or  double  quotes;
       there is no escape character. The ordering is little-endian (reversed),
       so that the  character  constant  abcd  denotes  0x64636261  and  not

       Local  labels  begin  with a period, and their ‘locality’ is granted by
       the assembler prepending the name of  the  previous  non-local  symbol.
       Thus  declaring  a  label  ‘.loop’  after  a label ‘label’ has actually
       defined a symbol called ‘label.loop’.

       SECTION name or SEGMENT name causes nasm to direct all  following  code
       to  the  named  section.  Section  names  vary with output file format,
       although most formats support the names .text, .data  and  .bss.   (The
       exception is the obj format, in which all segments are user-definable.)

       ABSOLUTE address causes nasm to position its notional assembly point at
       an  absolute  address: so no code or data may be generated, but you can
       use RESB, RESW and RESD to move the assembly point further on, and  you
       can  define  labels.  So  this  directive  may  be  used to define data
       structures. When you have finished doing absolute  assembly,  you  must
       issue another SECTION directive to return to normal assembly.

       BITS  16,  BITS  32  or BITS 64 switches the default processor mode for
       which nasm is generating code: it is equivalent to USE16  or  USE32  in
       DOS assemblers.

       EXTERN  symbol  and GLOBAL symbol import and export symbol definitions,
       respectively, from and to other modules. Note that the GLOBAL directive
       must appear before the definition of the symbol it refers to.

       STRUC  strucname  and  ENDSTRUC, when used to bracket a number of RESB,
       RESW or similar instructions, define a data structure. In  addition  to
       defining  the  offsets  of  the  structure  members, the construct also
       defines a symbol for the size of the structure,  which  is  simply  the
       structure name with _size tacked on to the end.

       ORG  address  is  used  by  the bin flat-form binary output format, and
       specifies the address at which  the  output  code  will  eventually  be

       GROUP  grpname  seg1  seg2...   is  used  by the obj (Microsoft 16-bit)
       output format, and  defines  segment  groups.  This  format  also  uses
       UPPERCASE,  which  directs  that  all  segment,  group and symbol names
       output to the object file should be in uppercase. Note that the  actual
       assembly is still case sensitive.

       LIBRARY  libname  is  used  by  the  rdf  output  format,  and causes a
       dependency record to be written to the output file which indicates that
       the program requires a certain library in order to run.

       Single-line  macros are defined using the %define or %idefine commands,
       in a similar fashion to the C preprocessor. They can be overloaded with
       respect  to  number  of  parameters,  although defining a macro with no
       parameters prevents the definition of any  macro  with  the  same  name
       taking  parameters, and vice versa.  %define defines macros whose names
       match  case-sensitively,  whereas  %idefine  defines   case-insensitive

       Multi-line macros are defined using %macro and %imacro (the distinction
       is the same as that between %define and %idefine), whose syntax  is  as

             %macro name minprm[-maxprm][+][.nolist] [defaults]
                      <some lines of macro expansion text>

       Again, these macros may be overloaded. The trailing plus sign indicates
       that any parameters  after  the  last  one  get  subsumed,  with  their
       separating  commas,  into  the last parameter. The defaults part can be
       used  to  specify  defaults  for  unspecified  macro  parameters  after
       minparam.  %endm is a valid synonym for %endmacro.

       To  refer to the macro parameters within a macro expansion, you use %1,
       %2 and so on. You can  also  enforce  that  a  macro  parameter  should
       contain a condition code by using %+1, and you can invert the condition
       code by using %-1.  You can also define a label  specific  to  a  macro
       invocation by prefixing it with a double % sign.

       Files can be included using the %include directive, which works like C.

       The preprocessor has a ‘context stack’, which may be used by one  macro
       to  store  information  that  a later one will retrieve. You can push a
       context on the stack using %push, remove one using %pop, and change the
       name of the top context (without disturbing any associated definitions)
       using %repl.  Labels and %define macros specific to the top context may
       be defined by prefixing their names with %$, and things specific to the
       next context down with %$$, and so on.

       Conditional assembly is done by means of  %ifdef,  %ifndef,  %else  and
       %endif  as  in C. (Except that %ifdef can accept several putative macro
       names, and will evaluate TRUE if any of them is defined.) In  addition,
       the  directives %ifctx and %ifnctx can be used to condition on the name
       of the top context on the context stack. The obvious set  of  ‘else-if’
       directives,  %elifdef,  %elifndef,  %elifctx  and  %elifnctx  are  also


       Please   report   bugs   through   the   bug   tracker   function    at


       as(1), ld(1).

                         The Netwide Assembler Project                 NASM(1)