Assembly Language

Assembly Language is a method of abstracting machine code instructions for a computer into commands recognizable by a human. Instead of dealing directly with bit sequences, programmers write programs in assembly by generating blocks of code using a small set of keywords (which are mapped to machine instructions by an assembler).

An example Hello World program written in pseudo-assembly for a MS-DOS-based system is listed below. Original source: Assembly Language for the IBM-PC.

---

 .data
   hello_message db 'Hello, World!',0dh,0ah,'$'
 
 .code
 main proc
   mov ax,@data
   mov ds,ax
 
   mov ah,9
   mov dx,offset hello_message
   int 21h
 
   mov ax,4C00h
   int 21h
 main endp
 end main

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Assembly programs are much easier to understand than their corresponding machine code instruction streams, which are just numbers, but they are much more difficult to comprehend than higher-level programming languages, such as PHP.