Page 15 - DCAP507_SYSTEM_SOFTWARE

Unit 1: Introduction to System Software

Interpreters Notes
Interpreter is a translator program that converts a statement of high-level language to machine
language and implements it instantly. The program instructions are taken line by line. The
interpreter reads the source program and accumulates it in memory. During interpretation, it
takes a source statement, identifies its meaning and carries out actions which increases it. This
involves computational and I/Oactions. Program Counter (PC) specifies which statement of the
source program is to be interpreted next. This statement would be subjected to the interpretation
cycle. The interpretation cycle includes the following steps:
 Fetch the statement.

 Scrutinize the statement and determine its meaning.
 Execute the meaning of the statement.
The following are the traits of interpretation:
 The source program is preserved in the source form itself, no target program exists.
 A statement is examined during the interpretation.

Assembler

An assembly language program is not directly executable. To be executed, first it is required to
change it into its machine language equivalent.
An Assembler is a program which is used to translate an assembly language program into its
machine level language equivalent. The program in assembly language is termed as source
code and its machine language equivalent is called object program.

Notes Once the object program is created, it is transferred into the computer's primary
memory using the system's loader. Here, another program called link editor passes
computer control to the first instruction in the object program, and then the execution
starts and proceeds till the end of the program.
Assembler is a program that automatically converts the source program written in assembly
language and to create as output an object code written in binary machine code.
The third party of language translator, an assembler translates only assembly language statements
into machine language. Assembly languages are utilized almost completely by professional
programmers to write competent programming code. An assembler functions like compiler,
generating a stored object module. A computer system usually functions only one assembly
language; thus, only one assembler is required. Users of any language translator program
should identify the difference between it and the programming language it converts.
A programming language is a set of rules for coding program commands, while a language
translator is a system software program that translates code written under the rules into the bits
and bytes that the computer recognizes. The translation into machine language appears while
the program executes. The third type of translator an assembler functions like a computer but it
translates only assembly language programs. An assembler is a language translator that translates
assembly language instruction into machine language. A language translator is a systems software
program that translates the programmer's applications program into machine language.

Example: If you generate a program in he BASIC or COBOL programming languages,
you cannot execute it on a computer until you summon the appropriate translator to paraphrase
your comments in machine language.

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