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--- en:multiasm:papc:chapter_6_12 [2025/11/16 15:23] – [Constants] ktokarz
+++ en:multiasm:papc:chapter_6_12 [2026/02/27 02:10] (current) – [Statements] jtokarz
@@ Line 1: / Line 1: @@
-====== MASM basics ======
+====== MASM Basics ======
 An assembler, understood as software that translates assembler source code into machine code, can be implemented in various ways. While the processor's instructions remain constant, other language elements may be implementation-specific. In this chapter, we present the most important language elements specific to the MASM assembly implementation. For a detailed description of MASM assembler language implementation, please refer to the Microsoft© website((https://learn.microsoft.com/en-us/cpp/assembler/masm/microsoft-macro-assembler-reference?view=msvc-170)).
 ===== Alphabet =====
@@ Line 195: / Line 195: @@
 Constants in an assembler program define the name for the value that can't be changed during normal program execution. It is the assembly-time assignment of the value and its name. Although their name suggests that their value can't be altered, it is true at the program run-time. Some forms of constants can be modified during assembly time. Usually, constants are used to self-document the code, parameterise the assembly process, and perform assembly-time calculations.
 The constants can be integer, floating-point numeric, or text strings.\\
-Integer numeric constants can be defined with the data assignment directives, **EQU** or the equal sign **=**. The difference is that a numeric constant defined with the EQU directive can’t be modified later in the program, while a constant created with the equal sign can be redefined many times in the program.
+Integer numeric constants can be defined with the data assignment directives, **EQU** or the equal sign **=**. The difference is that a numeric constant defined with the EQU directive can’t be modified later in the program, while a constant created with the equal sign can be redefined many times in the program. Numeric constants can be expressed as binary, octal, decimal or hexadecimal values. They can also be a result of an expression calculated during assembly time. It is possible to use a previously defined constant in such an expression.
 <code asm>
-int_const1 EQU 5
+int_const1 EQU 5                ; no suffix by default decimal value
-int_const2 = 7
+int_const_dec = 7               ; finished with "d", "D", "t", "T", or
+                                ; by default without suffix
+int_const_binary = 100100101b   ; finished with "b", "B", "y", or "Y"
+int_const_octal = 372o          ; finished with "o", "O", "q", or "Q"
+int_const_hex = 0FFA4h          ; finished with "h", or "H"
+int_const_expr = int_const_dec * 5
+</code>
+Floating-point numeric constants can be defined with the **EQU** directive only. The number can be expressed in decimal or scientific notation.
+<code asm>
+real_const1 EQU 3.1415          ; decimal
+real_const2 EQU 6.28e2          ; scientific
 </code>
-Floating-point numeric constants can be defined with the **EQU** directive only. The number can be expressed in decimal or scientific notation.
+Text string constants can be defined with **EQU** or **TEXTEQU** directives. Text constants assigned with the **EQU** or **TEXTEQU** directive can be redefined later in the program. The **TEXTEQU** is considered a text macro and is described in the section about macros.
 <code asm>
-real_const1 EQU 3.1415
+text_const1 EQU 'Hello World!'
-real_const2 EQU 6.28e2
+text_const2 EQU "Hello World!"
 </code>
-Text constant assigned with the EQU directive can be redefined later in the program.
-Integer constants:
-binary, 1b, 0101B, -10y, 111111Y
-octal, 34o, -746O, 2167q, 0Q
-decimal, 39, 12d, 1200D, -90t, 56T
-hex, 0h, 14A6h, 0FE3H
-.RADIX base directive:
-(.RADIX 16)
-Floating point constants:
-decimal notation, 1.0, 3.1415, -0.5
-exponent notation, 1e5, 1.56e-2, -15.7e+12
-String is an array of characters.
-‘Hello world’
-”123*x=???”
-Equal notations:
-mov BH,’A’
-mov BH,”A”
-mov BH,41h
@@ Line 254: / Line 243: @@
 All fields in a statement are optional. A statement can be composed of a label only (ended with a colon), an operation only (if it doesn't require operands), or a comment only. A few examples of proper statements are presented in the following code.
 <code asm>
-; name    ; operation ; operands ; comment
+; name ; operation ; operands ; comment
-cns_y      EQU         134       ; definition of a constant named cns_y with the value 134
+cns_y   EQU         134       ; definition of a constant named cns_y with the
+                              ;   value 134
-           .DATA                 ; operation only - directive to start data section
+        .DATA                 ; operation only - directive to start data section
-var_x      DB          123       ; definition of a variable named var_x with init value 123
+var_x   DB          123       ; definition of a variable named var_x with init
+                              ;   value 123
-           .CODE                 ; operation only - directive to start code section
+        .CODE                 ; operation only - directive to start code section
-begin:                           ; name only - label that represents an address
+begin:                        ; name only - label that represents an address
-           mov         rax, rbx  ; operation and corresponding operands
+        mov         rax, rbx  ; operation and corresponding operands
-                                 ; comment only statement
+                              ; comment only statement
-           END                   ; operation only - end of the source file
+        END                   ; operation only - end of the source file
 </code>

en/multiasm/papc/chapter_6_12.1763299407.txt.gz · Last modified: 2025/11/16 15:23 by ktokarz