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Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.
Every assembler may have it's own assembly language designed for a specific computers or an operating system.
Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.
Assembly language usually consists of three sections,
Data section
To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section
To declare variables
text section
_start specifies the starting of this section where the actually code is written.
There are various define directives to allocate space for variables for both initialized and uninitialized data.
| Define Directive | Description | Allocated Space |
|---|---|---|
| DB | Define Byte | 1 byte |
| DW | Define Word | 2 bytes |
| DD | Define Doubleword | 4 bytes |
| DQ | Define Quadword | 8 bytes |
| DT | Define Ten Bytes | 10 bytes |
| Define Directive | Description |
|---|---|
| RESB | Reserve a Byte |
| RESW | Reserve a Word |
| RESD | Reserve a Doubleword |
| RESQ | Reserve a Quadword |
| REST | Reserve a Ten Bytes |
Constants can be defined using
Loops are used to iterate a set of statements for a specific number of times.
where n specifies the no of times loops should iterate.
Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.