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assembly language[ə′sem·blē ‚laŋ·gwij]
a simple programming language; a system of commands for an arbitrary machine capable of carrying out elementary operations which are considerably more complex than those carried out by a given computer.
The most common assembly languages are one-to-one, in which the fundamental element of language (operator, variable) is converted into a single command upon translation into machine language. With the aid of a one-to-one assembly language, one can write any program that is possible for a computer. Programming in a one-to-one assembly language is equivalent to programming in machine language; nevertheless, it is more convenient for a programmer and accelerates the work approximately threefold.
Assembly languages other than one-to-one are not intended as systems of computer commands but rather as classes of problem solutions which considerably accelerate the work of programming; they do not permit writing a program of the same high quality attainable in principle by programming in machine language or a one-to-one assembly language. The fundamental element of language (the operator) in an assembly language of a type other than one-to-one is converted as a rule into a combination of commands upon translation into machine language. It is impossible to indicate the line of demarcation between assembly and other (more complex) programming languages. The BESM-6 and the Ural are examples of one-to-one assembly languages developed in the USSR. The Inzhener language for the Minsk computer is an example of a higher assembly language.
The algorithms given in assembly language are converted to a computer program by means of a so-called program translator, which can perform very simple storage distribution for the programmer; this program translator automatically arranges the program out of separate components by using the subprogram library and other operations.
In many automatic programming systems, the assembly language serves as an intermediate language in translation from some programming language into a machine language.
V. I. SOBEL’MAN
Assembly Language(language, robotics)
["The AL Language for an Intelligent Robot", T. Binford in Langages et Methods de Programation des Robots Industriels, pp. 73-88, IRIA Press 1979].
["AL User's Manual", M.S. Mujtaba et al, Stanford AI Lab, Memo AIM-323 (Jan 1979)].
Programming in assembly language is slow and error-prone but is the only way to squeeze every last bit of performance out of the hardware.
Filename extension: .s (Unix), .asm (CP/M and others).
See also second generation language.
assembly languageA programming language that is one step away from machine language. Each assembly language statement is translated into a machine instruction by the assembler. Programmers must be well versed in the computer's architecture, and, undocumented assembly language programs are difficult to maintain. Assembly languages are hardware dependent; there is a different one for each CPU series.
It Used to All Be Assembly Language
In the past, control programs (operating systems, database managers, etc.) and many applications were written in assembly language to maximize the machine's performance. Today, C/C++ is widely used instead. Like assembly language, C/C++ can manipulate the bits at the machine level, but it is also portable to different computer platforms. There are C/C++ compilers for almost all computers. See compiler.
Assembly Language vs. Machine Language
Although often used synonymously, assembly language and machine language are not the same. Assembly language is turned into machine language. For example, the assembly instruction compare a,b might be translated into COMPARE contents of bytes 32340-32350 with 54567-54577 (where A and B happen to be located in RAM at the moment). The actual binary format of the machine instruction is specific to the computer it is running in. See machine language.
They Can Be Quite Different
Assembly languages are quite different between computers as is evident below, which takes 16 lines of code for the HP and 82 lines for the x86. This example changes Fahrenheit to Celsius.
HP 3000 begin intrinsic read,print,binary,ascii; array buffer(0:17); array string(0:3); byte array b'string(*) = string; integer ftemp, ctemp, len; move buffer:= "Enter Fahrenheit "; print (buffer,-30,%320); len:=read (string,-4); ftemp:= binary(b'string,len); ctemp:= (ftemp-32) * 5 / 9; len:= ascii(ctemp,1-,b'string); move buffer:= "Celsius is "; move buffer(14) := string, (-len); print (buffer,-32,%0); end PC (Intel x86) cseg segment para public 'CODE' assume cs:cseg,ds:cseg start: jmp start1 msgstr db 'Enter Fahrenheit ' crlf db 13,10,'$' nine db 9 five db 5 outstr db 'Centrigrade is $' start1: push ds push cs pop ds mov dx,offset cseg:msgstr mov ah,9 int 21h sloop: cent: call getnumb test ax,ax je exit push ax mov dx,offset cseg:outstr mov ah,9 int 21h pop ax sub ax,32 jns c1 push ax mov dl,'-' mov ah,6 int 21h pop ax neg ax cl: mul five div nine call putval mov dx,offset cseg:crlf mov ah,9 int 21h jmp sloop exit: pop ds mov ah,4ch int 21h getnumb: xor bx,bx llp: mov dl,0ffh mov ah,1 int 21h cmp al,0dh je llr sub al,'0' jb llr cmp al,'9' ja llr xor ah,ah shl bx,1 add ax,bx shl bx,1 shl bx,1 add bx,ax jmp llp llr: mov dx,offset cseg:crlf mov ah,9 int 21h mov ax,bx ret putval: xor bx,bx push bx mov bx,10 llg: xor dx,dx div bx add dx,'0' push dx test ax,ax jne llg bloop: pop dx test dx,dx je endx mov ah,6 int 21h jmp bloop endx: ret cseg ends end start