Technology Stuff : The Assembly Language Level

The assembly language level differs in a significant respect from the micro architecture, ISA, and operating system machine levels- it is implemented by translators rather than by interpretation.

Translator: Program that convert a user's program written in some language to another language are called translator.

Source Language: The language in which the original program is written is called the source language.

Target Language: The language to which it is converted is called the target language.

Difference between translation and interpretation

In translation, the original program in the source language (C, C++, or JAVA) is not directly executed. Instead, it is converted to an equivalent program called an object program (.obj) or executable binary program (.class, .exe) whose execution is carried out only after the translation has been completed.

Generation of an equivalent program in the target language
Execution of newly generated language

These two steps do not occur simultaneously. The second step does not begin until the first has been completed.

"When the source language is essentially a symbolic representation for a numerical machine language, the translator is called an assembler and the source language is called an assembly language. "

Assembly Language:

each statement produces exactly one machine instruction
much easier code than in machine language
combination of symbolic names and symbolic addresses
It has access to all the features and instruction available on the target machine
an assembly language program can run only one family of machines

Macros:

A macro definition is a way to give name to a piece of text. After a macro has been defined, the programmer can write the macro name instead of the piece of program

Example:

   SWAP MACRO
   MOV EAX,P
   MOV EBX,B
   MOV Q,EAX
MOV P,EBX
ENDM

SWAP
SWAP

Courtesy: Andrew S. Tanenbaum, Structured Computer Organization (Fifth Edition)

Sunday, December 2, 2012

The Assembly Language Level