SYSTEM PROGRAMMING
& SYSTEM
ADMINISTRATION
UNIT-1
What Is System Program
System Programs were developed to
make computers better adapted to the
needs of their users.
 Some examples of system program are:
• Compliers
• Loaders
• Macro processors
• Operating systems

Brief Introduction
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


Complier:- They are systems programs
that accept people-like languages &
translate them into machine language.
Loaders:- They prepare machine
language program for execution.
Macro processors:- They allow
programmers to use abbreviations.
Operating Systems & file system:-They
allow flexible storing & retrieval of
information.
ASSEMBLERS



It is difficult for programmers to write or
read programs in machine language.
So they began to use a mnemonic
(symbol) for each machine instruction
,which they would subsequently translate
into machine language.
Such a mnemonic language is known as
ASSEMBLY LANGUAGE.
ASSEMBLERS cont….
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
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Assemblers are programs written to
automate the translation of assembly
language in to machine language.
The input to an assembler program is
called the source program.
The output is a machine translation (object
program).
ASSEMBLERS cont….

1.
2.
3.
An assembly language is a machine
dependent, low level programming
language which is specific to a certain
computer system . Three basic features
which simplify programming :
Mnemonic operation codes
Symbolic operands
Data declarations
Execution of program written in
a language L involves the
following steps
1.
2.
3.
4.
Translation of the program- by translator
Linking of the program with other programs
needed for its execution-by linker
Relocation of the program to execute from
the specific memory area allocated to it
Loading of the program in the memory for
the purpose of execution-by loader
Program Execution
Data
Translator
Linker
Loader
Binary
Program
Results
Source Program
Objects
Modules
Binary
Programs
Data flow
Control flow
LOADERS
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
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A loader is a program that places
programs into memory & prepares them
for execution.
In a simple loading scheme, the assembler
outputs the machine language translation
of a program on a secondary device & a
loader is placed in core (memory).
Subroutines:- It is a body of computer
instruction designed to be used by others
routines to accomplish a task.
LOADERS cont….
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Two types of subroutines are
Closed subroutines: It can be stored
outside the main routine &control transfers
to the subroutine.
Open subroutines : It is one whose code is
inserted into main program.
MACROS


Macro processing facility which permits
the programmer to define an abbreviation
for a part of his program & to use the
abbreviation in his program.
The macro processor treats the identical
parts of program defined by the
abbreviation as a macro definition & saves
the definition.
COMPLIERS
A complier is a program that accepts a
program written in a high level language &
produces an object program.
 Example of high-level language are:
 FORTRAN
 COBOL
 ALCOL
 Interpreter : It is a program that appears
to execute a source program as if it were
machine language.

SOFTWARE TOOLS
Program that help in developing &
using other programs. These
programs, called software tools.
 Definition:- A software tool is a system
program which
1. Interfaces a program with the entity
generating its input data.
2. Interfaces the results of a program
with the entity consuming them.

A Software tool
Originator
Software
Raw Program
or Data
Consumer
Transformed
Program or Data
A Software tool
Software Tools For Program
Development
1.
2.
3.
4.
5.
6.
Program design, coding, &
documentation
Preparation of programs in machine
readable form
Program translation, linkage & loading
Program testing & debugging
Performance tuning
Reforming the data and/or results of a
program to suit other programs.
1. Program Design & Coding

1.
2.
Two categories of tools used in program
design & coding are
Program generators:- It generates a
program which performs a set of
functions described in its specification
Programming environments:-It
supports program coding by
incorporating awareness of the
programming language syntax &
semantics in the lang. editor
2. Program Entry & Editing


1.
2.
These are text editors or more
sophisticated programs with text editors
as front ends.
The editor functions in 2 modes:Command mode
Data mode
Program Testing & Debugging
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1.
2.
3.
4.
Main steps in this are selection of test
data for the program, analysis of test
results to detect errors,& debugging i.e.
localization & removal of errors.
Software tools to assist the programmer
in these steps are:Test data generators
Automated test drivers
Debug monitors
Source code control systems
EDITORS

1.
2.
3.
4.
5.
Forms of Editors
Line Editors
Steam Editors
Screen Editors
Word Processors
Structure Editors
EDITORS cont…

Line Editors:- The scope of edit
operations in a line editor is limited to a
line of text. The line is designed
positionally,e.g. by specifying its serial
number in the text, or contextually, e.g. by
specifying a context which uniquely
identifies it.
EDITORS cont…

Stream Editors:- A stream editor
views the entire text as a stream of
characters. They typically supports
characters, line, & context oriented
commands based on the current
editing context indicated by the
position of a text pointer.
EDITORS cont…

Screen Editors: - A line or stream
editors does not display the text in the
manner it would appear if printed. A screen
editor uses the what-you –see-is-whatyou-get principle in editor design. This is
very useful while formatting the text to
produce printed documents.
EDITORS cont…

Word processors:- They are document
editors with additional features to produce
well formatted hard copy output.
Essentials features are commands for
moving sections of text from one place to
another, merging of text, & searching &
replacement of words. Many word
processor support a spell-check option.
EDITORS cont…

Structures Editors:- A structure editor
incorporates an awareness of the structure
of a document. This is useful in browsing
through a document ,e.g. if a programmer
wishes to edit a specific function in a file.
DEBUG MONITORS

1.
2.
3.
4.
5.
It provide the following facilities for
dynamic debugging :
Setting breakpoints in the program
Initiating a debug conversation when
control reaches a breakpoint
Display values of variables
Assigning new values to variables
Testing user defined assertions &
predicates involving program variables.
DEBUG MONITORS

1.
2.
The sequence of steps involved in
dynamic debugging of a program is as
follows:
The user complies the program under the
debug option. The compiler produces two
files- the compiled code file & the debug
information file.
The user activates the debug monitor &
indicates the name if the program to be
debugged .
DEBUG MONITORS cont…
2.
3.
The debug monitor opens the compiled
code & debug information files for the
program.
The user specifies his debug
requirements – a list of breakpoints &
actions to be performed at breakpoints.
The debug monitor instruments the
program, & builds a debug table
containing the pairs .
DEBUG MONITORS cont…
4.
5.
The instrumented program gets control &
executes up to a breakpoints.
A software interrupt is generated when
the <SI_instrn> is executed. Control is
given to the debug monitor which
consults the debug table & performs the
debug actions specified for the
breakpoints .
DEBUG MONITORS cont…
6.
A debug conversation is now opened
during which the user may issue some
debug commands or modify breakpoints
& debug actions associated with
breakpoints.
Steps 4 & 5 are repeated until the end if
the debug session.
PROGRAMMING ENVIRONMETS

1.
2.
3.
4.
A programming environment is a
software system that provides integrated
facilities for program creation, editing,
execution , testing, & debugging. It
consists of the following components :
A syntax directed editor (which is a
structure editor)
A language processor –a complier,
interpreter, or both
A debug monitor
A dialog monitor