MASM:如何解决错误“不允许立即操作数"? [英] MASM: how to resolve error "immediate operand not allowed"

问题描述

我的汇编程序具有以下结构:

My assembly program has following structure:

BPB_FAT16   STRUCT                     ; Base BPB_FAT16. Size=0x19=25.
BytesPerSector      DW  0x0200 ; Size of HW sector, usualy 512.
SectorsPerCluster   DB  0x01   ; Valid values 1,2,4,8,16,32,64,128.
ReservedSectors     DW  0x0001 ; NrOfSectors preceding FAT.
NumberOfFats        DB  0x02   ;
RootEntries         DW  0x00E0 ; Max number of YWORD entries in the 
                               ;root dir.
SmallSectors        DW  0x0B40 ; See also .LargeSectors.
MediaDescriptor     DB  0xF0   ; 0xF0 floppy disk, 0xF8 hard disk.
SectorsPerFat       DW  0x0009 ;
SectorsPerTrack     DW  0x0012 ;
NumberOfHeads       DW  0x0002 ;
HiddenSectors       DW 0x00000000
LargeSectors        DW 0x00000000
                               ; Extended BPB_FAT16. Size=0x1A=26.
PhysicalDriveNumber DB 0x00   ; 0x00 floppy disk, 0x80 hard disk.
Reserved            DB 0x00   ;
ExtBootSignature    DB 0x29   ; Or 0x28.
VolumeSerialNumber  DW 1212121 ; Randomly generated number.
VolumeLabel         DB "NO NAME    " ; Space-padded to size=11.
FileSystemType      DB "FAT12   "    ; Space-padded to size=8.
BPB_FAT16 ENDS  ;   Total BPB_FAT16. Size=0x33=51.

我的程序仅对下面给出的一行代码显示两个错误:

My program is showing two errors for only one line of code given below:

Bpb   BPB_FAT16{}

这两个错误是:

error1: missing operator in expression
error2: initializer magnitude too large for specified size

我该怎么办?请引导我.

What should I do? Please guide me.

推荐答案

在将0x前缀用作十六进制值的每一行上都可能出现错误消息missing operator in expression. MASM不支持该功能，它使用h后缀表示十六进制值.

The error message missing operator in expression is likely occurring on every line where you use 0x prefix for hexadecimal values. MASM doesn't support that and it use the h suffix to denote hexadecimal values.

错误initializer magnitude too large for specified size是因为值1212121 不能适合您为VolumeSerialNumber指定的DW(16位WORD). BPB中的VolumeSerialNumber必须是DD(32位DWORD).

The error initializer magnitude too large for specified size is because the value 1212121 can't fit in the DW (16-bit WORD) you specified for VolumeSerialNumber. VolumeSerialNumber in a BPB needs to be a DD (32-bit DWORD).

尽管它不会产生错误，但BPB中的字段HiddenSectors和LargeSectors是32位DWORD，因此它们应使用类型DD而不是DW.

Although it didn't generate an error, the fields HiddenSectors and LargeSectors in a BPB are a 32-bit DWORD so they should be using the type DD instead of DW.

您的结构本可以定义为:

Your structure could have been defined as:

BPB_FAT16   STRUCT                   ; Base BPB_FAT16. Size=0x19=25.
BytesPerSector      DW  200h         ; Size of HW sector, usualy 512.
SectorsPerCluster   DB  1h           ; Valid values 1,2,4,8,16,32,64,128.
ReservedSectors     DW  1h           ; NrOfSectors preceding FAT.
NumberOfFats        DB  2h           ;
RootEntries         DW  0E0h         ; Max number of YWORD entries in the
                                     ; root dir.
SmallSectors        DW  0B40h        ; See also .LargeSectors.
MediaDescriptor     DB  0F0h         ; 0xF0 floppy disk, 0xF8 hard disk.
SectorsPerFat       DW  9h           ;
SectorsPerTrack     DW  12h          ;
NumberOfHeads       DW  2h           ;
HiddenSectors       DD  0h
LargeSectors        DD  0h
                                     ; Extended BPB_FAT16. Size=0x1A=26.
PhysicalDriveNumber DB  0h           ; 0x00 floppy disk, 0x80 hard disk.
Reserved            DB  0h           ;
ExtBootSignature    DB  29h          ; Or 0x28.
VolumeSerialNumber  DD 1212121       ; Randomly generated number.
VolumeLabel         DB "NO NAME    " ; Space-padded to size=11.
FileSystemType      DB "FAT12   "    ; Space-padded to size=8.
BPB_FAT16 ENDS  ;   Total BPB_FAT16. Size=0x33=51.

通过这些更改，您的结构现在正好是51个字节，这就是您期望的FAT16

With these changes your structure is now exactly 51 bytes which is what you'd expect for a FAT16 DOS 4.0 EBPB.

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