Constants in Assembly Language

Assembly language doesn’t have built-in support for constants in the same way as high-level languages. However, we can simulate constants using assembly directives. Here’s an example that demonstrates the concept:

section .data
    s db 'constant', 0    ; Define a string constant
    n equ 500000000       ; Define a numeric constant
    d equ 3e20 / n        ; Constant expression (not supported in most assemblers)

section .text
global _start

_start:
    ; Print the string constant
    mov eax, 4            ; sys_write system call
    mov ebx, 1            ; file descriptor (stdout)
    mov ecx, s            ; pointer to the string
    mov edx, 8            ; length of the string
    int 0x80              ; call kernel

    ; Exit the program
    mov eax, 1            ; sys_exit system call
    xor ebx, ebx          ; exit code 0
    int 0x80              ; call kernel

In assembly language, we use directives to define constants:

• The db directive is used to define a string constant s.
• The equ directive is used to define numeric constants n and d.

Note that assembly language doesn’t support constant expressions or arbitrary precision arithmetic directly. The calculation of d as shown in the example (3e20 / n) would typically be done at compile-time by the assembler, if supported.

To use these constants, we simply reference them by name in our code. The assembler will replace these references with their actual values during the assembly process.

Assembly language doesn’t have built-in functions for mathematical operations like sine. Such operations would typically be implemented using external libraries or custom implementations.

To run this assembly program:

1. Save the code in a file (e.g., constants.asm)
2. Assemble it into an object file:

   nasm -f elf constants.asm

3. Link the object file to create an executable:

   ld -m elf_i386 -o constants constants.o

4. Run the program:

   ./constants

This will output the string “constant” to the console.

Remember, assembly language is low-level and platform-specific. This example is for x86 assembly on a Linux system. The exact syntax and system calls may vary on different architectures or operating systems.