[MASM]Another 'cannot use 16-bit register with a 32-bit address' error

Question

I'm learning assembly language with MASM assembler and I get stuck when I tried to assemble a simple file using this command :ml /c test.asm and the test.asm file looks like :

.386
.model flat
.code
MOV BP,WORD PTR[BP+4]
END

then the problem comes:

Microsoft (R) Macro Assembler Version 6.14.8444

Copyright (C) Microsoft Corp 1981-1997. All rights reserved.

Assembling: test.asm

test.asm(4) : error A2155: cannot use 16-bit register with a 32-bit address

the question is ,

32-bit address?I didn't tell the assembler to use a 32-bit address.

and How can I get my code passed?

Answer 1

I've done some researches and here is what I've learned

.MODEL directive

• enables use of simplified segments
• controls the name of the code segment
• controls the default distance for procedures.

the syntax is :.MODEL memorymodel, options-optional

and memorymodel can be TINY, SMALL, COMPACT, MEDIUM, LARGE, HUGE,or FLAT

Flat model is similar to tiny model in that all code and data go in a single 32-bit -addressable block of memory.

To write a flat model program, specify the .386 or .486 directive before.

so the directive .386is optional if I don't want to use flat model (look here)

here are some references

1 .MODEL

2 Logical Segments and Memory Model Directives