DOCERR: MASM 6.0 Programmer's Guide Errors: Chapter 7

ID: Q73746

The information in this article applies to:

Microsoft Macro Assembler for MS-DOS and OS/2, versions 6.0, 6.0a, 6.0b

SUMMARY

The following is a list of documentation additions and corrections for chapter 7 of the "Microsoft Macro Assembler Programmer's Guide" version 6.0 manual. The section and page numbers are listed first, followed by a description of the addition or correction.

Section 7.1, Page 167

The first paragraph of this section should read:

Jumps are the most direct method for changing program control from one location to another. At the processor level, jumps work by changing the value of the IP (Instruction Pointer) for near jumps, and by changing the values of the CS and IP registers for far jumps. The IP register is loaded with the offset of the target address and CS is loaded with the segment of the target address. The many forms of the jump instruction handle jumps based on conditions, flags, and bit settings.

Section 7.1.1.2, Page 169

The sample line


   jmp ebx     ; FAR32 jump

should read:


   jmp ebx     ; NEAR32 jump

In addition, replace FAR32 with NEAR32 in the sentence before the above line.

Section 7.1.1.2, Page 170

The example shows the following TYPEDEF statement:


   NPVOID  TYPEDEF NEAR PTR VOID

Note that VOID is not a defined type. It acts as a placeholder and improves program readability. In this case, the TYPEDEF is equivalent to:


   NPVOID  TYPEDEF NEAR PTR

Section 7.1.2.2, Page 173

Table 7.1, on page 173, uses the same character for the number zero and the letter "O." This may cause some confusion when reading the table. The "OF" indicates the overflow flag and does not represent the hexadecimal number 0F.

Section 7.1.2.6, Page 176

In the sample code, the line


  .IF  cx = 20

should be:


  .IF  cx == 20

Section 7.2, Page 177

The description of the LOOPE, LOOPZ, LOOPNE, and LOOPNZ states:

Loops while equal (or not equal). Checks CX and a condition. The loop ends when the condition is true. Set CX to a number out of range if you don't want to control the loop.

It should read:

Loops while equal (or not equal). Checks CX and a condition (indicated by the zero flag). The loop continues while the condition is met and CX is not zero. Set CX to a number out of range if you don't want the CX count to control the loop.

Section 7.3.2, Page 187

The sample program contains a line that states:


   mov sp, bp

Because there are no local variables and the SP register is not otherwise modified, this line is not needed.

Section 7.3.3.2, Page 191

This first paragraph states:

The parameters are separated from the reglist by a comma if there is a list of registers.

According to the BNF grammar shown in Appendix B, the above statement is incorrect. The comma is optional and is required only if the parameters are placed on the next line.

For example,


   myproc PROC FAR C PUBLIC USES di si, var1:word, arg1:VARARG

is equivalent to:


   myproc PROC FAR C PUBLIC USES di si var1:word, arg1:VARARG

Note in the last case there is no comma following the SI register.

Section 7.3.3.3, Page 193

The sample program contains the line:


   dec arg1

It should read:


   dec argcount

Section 7.3.6, Page 199

Page 199 shows two sample lines for declaring prototypes. They are:


   addup  PROTO NEAR C argcount:WORD, arg2:WORD, arg3:WORD

   myproc PROTO FAR  C, argcount:WORD, arg2:VARARG

The last prototype has a comma following the C language specifier while the first prototype does not. The documentation fails to mention that the comma is optional; therefore, both statements are correct.

Section 7.3.7.5, Page 202 and 203

In the first example, the code is missing a few steps. The following is the corrected code:


   .CODE
   mov      bx, pfunc                  ; pfunc is the Function Table
   mov      si, Num                    ; Num contains 0 or 2
   INVOKE   FUNCPTR PTR [bx+si], 1, 1  ; Selects proc1 or proc2

The first paragraph on page 203 states:

You can also use ASSUME to accomplish the same task. The ASSUME statement associates the type PFUNC with the BX register.

It should read:

You can also use ASSUME to accomplish the same task. In the sample below, the ASSUME statement associates the type FUNCPTR with the BX register.

In the example that follows, add the following line after the ASSUME:


   mov      bx, pFunc

Change the INVOKE line to read:


   INVOKE   [bx+si], 1, 1

Section 7.3.8.2, Page 205

Page 205 shows the epilogue code when <LOADDS> is specified on a PROC line. One line states:


   mov sp,bp

It should read:


   mov sp,bp      ; if localbytes is not 0

Section 7.4.1, Page 209

The sample code demonstrates how to print a message on the display using a DOS interrupt call. It shows the following code:


   .DATA
   msg BYTE "This writes to the screen",$
   .CODE
   mov dx,offset msg
   mov ah,09h
   int 21h

It should read:


   .DATA
   msg BYTE "This writes to the screen$"
   .CODE
   mov ax,SEG msg
   mov ds,ax
   mov dx,offset msg
   mov ah,09h
   int 21h

Section 7.4.2, Page 211

The last paragraph states:

To replace the address in the interrupt descriptor table with the address of your procedure, AL needs to be loaded with 04h and AH loaded with 35, the Get Interrupt Vector function. The Set Interrupt Vector function requires 25 in AH.

The numbers 35 and 25 are presented in hexadecimal rather than decimal. They should be written as 25h and 35h.

Section 7.4.2, Page 212

Change the line


   .MODEL LARGE,C,DOS

to:


   .MODEL LARGE,C,OS_DOS

Also, the last sentence on page 212 should read:

Before your program ends, you should restore the original address by loading DS and DX with the original interrupt address and using the DOS set vector function to store the original address at the correct location.

Additional query words: 6.00 6.00a 6.00b

Keywords :
Version : MS-DOS:6.0,6.0a,6.0b
Platform : MS-DOS
Issue type :