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    Assemble command

    Purpose:  To assemble IBM Personal Computer Macro Assembler language
              statements directly into memory.

    Format:   A [address]

    Remarks:  All numeric input to the Assemble command is in hexadecimal.
              The assembly statements you enter are assembled into memory
              at successive locations, starting with the address specified
              in address. If no address is specified, the statements are
              assembled into the area at CS:0100h, if no previous Assemble
              command was issued, or into the location following the last
              instruction assembled by a previous Assemble command. When
              all desired statements have been entered, press Enter when
              you are prompted for the next statement, to return to the
              DEBUG prompt.

              DEBUG responds to invalid statements by displaying:

              ^error

              and redisplaying the current assemble address.

              DEBUG supports standard 8088/8086 assembly language syntax
              (and the 8087) instruction set), with the following rules:

              .   All numeric values entered are hexadecimal and can be
                  entered as 1-4 characters.

              .   Prefix mnemonics must be entered in front of the opcode
                  to which they refer. They can also be entered on a sepa-
                  rate line.

              .   The segment override mnemonics are CS:, DS:, ES:, and
                  SS:.

              .   String manipulation mnemonics must explicitly state the
                  string size. For example, MOVSW must be used to move word
                  strings and MOVSB must be used to move byte strings.

              .   The mnemonic for the far return is RETF.

              .   The assembler will automatically assemble short, near,
                  or far jumps and calls depending on byte displacement to
                  the destination address. These can be overridden with
                  the NEAR or FAR prefix. For example:

                  0100:0500 JMP 502       ;A 2 byte short jump
                  0100:0502 JMP NEAR 505  ;A 3 byte near jump
                  0100:0505 JMP FAR 50A   ;A 5 byte far jump

                  The NEAR prefix can be abbreviated to NE, but the FAR
                  prefix cannot be abbreviated.

              .   DEBUG cannot tell whether some operands refer to a word
                  memory location or a byte memory location. In this case,
                  the data type must be explicitly stated with the prefix
                  WORD PTR or BYTE PTR. DEBUG will also accept the abbre-
                  viations WO and BY. For example:

                  NEG   BYTE PTR [128]
                  DEC   WO [SI]

              .   DEBUG also cannot tell whether an operand refers to a
                  memory location or to an immediate operand. DEBUG uses
                  the common convention that operand enclosed in square
                  brackets refer to memory. For example:

                  MOV   AX,21         ;Load AX with 21h
                  MOV   AX,[21]       ;Load AX with the contents of
                                      ;  memory location 21h

              .   Two popular pseudo-instructions have also been included.
                  The DB opcode assembles byte values directly into memo-
                  ry. The DW opcode assembles word values directly into
                  memory. For example:

                  DB   1,2,3,4,"This is an example"
                  DB   "This is a quote: "'
                  DB   "This is a quote:'"
                  DW   1000,2000,3000,", BACH:"

              .   All forms of the register indirect commands are support-
                  ed. For example:

                  ADD     BX,34[BP+2].[SI-1]
                  POP     [BP+DI]
                  PUSH    [SI]

              .   All opcode synonyms are supported. For example:

                  LOOPZ   100
                  LOOPE   100
                  JA      200
                  JNBE    200

              .   For 8087 opcodes the WAIT or FWAIT prefix must be ex-
                  plicitly specified. For example:

                  FWAIT FADD ST,ST(3)   ;This line will assemble
                                        ;  an FWAIT prefix
                  FLD TBYTE PTR [BX]    ;This line will not


    Example:  C>debug
              -a200
              08B4:0200 xor ax,ax
              08B4:0202 mov [bx],ax
              08B4:0204 ret
              08B4:0205