Assembly Language: Difference between revisions
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'''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]]). | |||
Assemblers not only relieve the programmer of remembering instruction codes, but allow symbolic reference to memory locations, further improving redability. | |||
. | An example [[Hello World]] program written in pseudo-assembly for a [[MS-DOS]]-based system is listed below. Original source: [http://www2.latech.edu/~acm/helloworld/asm.html Assembly Language for the IBM-PC]. | ||
mov ah,9 | ----- | ||
.data | |||
hello_message db 'Hello, World!',0dh,0ah,'$' | |||
.code | |||
main proc | |||
main endp | mov ax,@data | ||
end main | mov ds,ax | ||
mov ah,9 | |||
mov dx,offset hello_message | |||
int 21h | |||
mov ax,4C00h | |||
int 21h | |||
main endp | |||
end main | |||
----- | ----- | ||
Assembly programs are much easier to understand than their corresponding machine code instruction streams, but they are much more difficult to comprehend than, | Assembly programs are much easier to understand than their corresponding machine code instruction streams, which are just numbers, but they are much more difficult to comprehend than most general-purpose higher-level [[programming languages]], such as the [[C programming language]] or [[Java]]. There are, however, higher-level programming languages such as [[APL]] that are unreadable by other than a specialist. | ||
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Latest revision as of 16:38, 9 January 2010
Assembly language is a method of abstracting machine code instructions for a computer into commands recognizable by a human. Instead of dealing directly with bit sequences, programmers write programs in assembly by generating blocks of code using a small set of keywords (which are mapped to machine instructions by an assembler).
Assemblers not only relieve the programmer of remembering instruction codes, but allow symbolic reference to memory locations, further improving redability.
An example Hello World program written in pseudo-assembly for a MS-DOS-based system is listed below. Original source: Assembly Language for the IBM-PC.
.data hello_message db 'Hello, World!',0dh,0ah,'$' .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
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 most general-purpose higher-level programming languages, such as the C programming language or Java. There are, however, higher-level programming languages such as APL that are unreadable by other than a specialist.