Q49707: Shifting (SHL) Using an 8-Bit Constant

Article: Q49707
Product(s): See article
Version(s): 5.10   | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_masm
Last Modified: 29-MAR-1990

Problem:

Page 96 of the "Microsoft Macro Assembler for MS OS/2 and MS-DOS
Operating Systems: Version 5.1 Update" says that I can use the
shift-left instruction (SHL) with an 8-bit constant. Yet, when I
assemble my source code, I get the following error:

   A2052: Improper operand type

Response:

The third paragraph on Page 96 states the following:

   On the 8088 and 8086, the source operand can be either CL or 1. On
   the 80186-80386 processors, the source operand can be CL or an
   8-bit constant.

To use the 8-bit constant, you must specify that you are writing 186,
286, or 386 code. The assembler assumes the worst and defaults to the
8088 options and doesn't accept the 8-bit constant.

The following code generates the error:

.model small
.code
shl bl,2
end

To correct the problem, use the .186, .286, or .386 directive such as
the following:

.model small
.286
.code
shl bl,2
end

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