TELECOMPUTING-^? - Bombjack.org

INTRODUCTION TO
ASSEMBLY
LANGUAGE
COMPUTERS DON'T SPEAK ENGLISH, THEY SPEAK MACHINE
CODE. AND (MOST) HUMANS DON'T SPEAK MACHINE CODE,
BUT SOMETIMES WE FIND WE HAVE TO TALK TO COMPUTERS.
WHEN THIS NEED ARISES WE USE AN INTERPRETER, JUST AS
WE DO WHEN WE HAVE TD TALK TO ANOTHER HUMAN WHO
DOESN'T SPEAK OUR LANGUAGE. THE HUMAN-TO-MACHINE
INTERPRETER MOST OF US ARE USED TO IS BASIC. IT LETS
US PUT DOWN OUR IDEAS IN A FORM OF "PIDGIN ENGLISH"
THAT WE CAN UNDERSTAND, AND TRANSLATES IT INTO
MACHINE CODE THAT THE COMPUTER CAN EXECUTE. THE
PROCESS IS NOT VERY EFFICIENT, BECAUSE ENGLISH IS A
MUCH MORE GENERAL LANGUAGE THAN MACHINE CODE. EVEN A
SIMPLE COMMAND LIKE "PRINT" MUST BE TRANSLATED INTO A
LOT OF NUMBERS (THE MACHINE CODE) FOR THE COMPUTER TO
RUN. THE BASIC INTERPRETER MUST ALSO EXAMINE THE
"PRINT" STATEMENT IN THE CONTEXT OF THE PROGRAM TD
SEE IF WE WANTED A STRING, A STRING VARIABLE, A
NUMBER, A VARIABLE, A NUMERIC EXPRESSION, OR A BLANK
LINE PRINTED, AND WHETHER WE WANTED IT PRINTED TO THE
SCREEN, PRINTER, OISK DRIVE, CASSETTE, OR MODEM.
THAT TAKES TIME.
IT WOULD BE MUCH FASTER IF WE COULD SPEAK SOME
DIALECT OF THE COMPUTER'S LANGUAGE, SOMETHING AS
SPECIFIC AS MACHINE CODE BUT EASIER FOR A HUMAN TO
UNDERSTAND. THIS IS THE PRINCIPLE BEHIND ASSEMBLY
LANGUAGE. EACH COMMAND IN ASSEMBLY LANGUAGE IS A
MNEMONIC (LETTERS THAT ARE AN ABBREVIATION FOR
SOMETHING ELSE) THAT CORRESPONDS DIRECTLY WITH A
SINGLE MACHINE CODE INSTRUCTION. FOR EXAMPLE, THE
ASSEMBLY LANGUAGE COMMAND "LDA" STANDS FOR "LOAD THE
ACCUMULATOR". THE ASSEMBLER WILL TRANSLATE THIS INTO
JUST ONE MACHINE CODE INSTRCTION, THE NUMBER THAT
MEANS TO THE COMPUTER "LOAD THE ACCUMULATOR." AS YOU
CAN SEE, ASSEMBLY LANGUAGE PROGRAMMING DOES REQUIRES
THAT YOU UNDERSTAND WHAT HAPPENS INSIDE YOUR
COMPUTER. YOU HAVE TO KNOW ABOUT MEMORY ADDRESSING
MODES, THE CPU REGISTERS, FLAGS, BINARY LOGIC.
HEXADECIMAL NUMBERS, AND HOW INPUT AND OUTPUT ARE
HANDLED. DON'T LET THIS DISCOURAGE YOU! COMPUTERS
ARE REALLY VERY SIMPLE DEVICES, AND DO EXACTLY AS
THEY ARE TOLD. ONE GOOD BOOK AND A LITTLE TIME ARE
ALL YOU WILL NEED TO GET STARTED. REMEMBER, ONCE
UPON A TIME EVEN BASIC LOOKED LIKE A FOREIGN LANGUAGE
TO YOU! (IF YOU DON'T SPEAK BASIC OR SOME OTHER
HIGH-LEVEL COMPUTER LANGUAGE YET, I STRONGLY
RECOMMEND GAINING SOME FAMILIARITY WITH BASIC, COMAL,
PASCAL, OR SOMETHING ELSE BEFORE TAKING ON ASSEMBLY
LANGUAGE, JUST TO BECOME FAMILIAR WITH PROGRAMMING
STRUCTURE AND LOGIC. YOU DON'T HAVE TO BE AN EXPERT
IN ANOTHER PROGRAMMING LANGUAGE BEFORE TACKLING
ASSEMBLY, BUT SOME FAMILIARITY DEFINITELY HELPS.)
MUtK
BROWN
in this entry-level tutorial,
you will not only lose your fear
of assembly language, but you
will actually customize BASIC
with a short but useful routine.
Remember, once upon a tine
even BASIC looked like a
foreign language to you!
Computers are really very
simple devices, and do
exactly as they are told.
Even a
"PRINT1 1 must
into a
simple
lot of
the computer
command like
be translated
numbers
to run.
.. for