#!/usr/local/bin/perl
#
# Program to open the password file, read it in,
# print it, and close it again.

$file = '/etc/passwd';		# Name the file
open(INFO, $file);		# Open the file
@lines = <INFO>;		# Read it into an array
close(INFO);			# Close the file
print @lines;			# Print the array

Firstly Lets see what is OSI = Open Systems Interconnect

To start with there are 7 layers and here is a picture showing the same.

Couple of months back i gave a try and installed UBUNTU and i love it. Here is what i found

• Don’t have to worry about Virus protection software,
• Can practice shell scripting,
• It is fast,
• Install Apache, still my PC was fast.
• No POP-UP’s while browsing.
• No need for a firewall.
• Automatic Updtes
  

Some Drawback thoug.

• Took me a while to set up my Wireless at home.

Initial :All statements in the initial block are executed only once during a simulation.if there are multiple initial blocks each block starts to execute simultaneously at time 0 only once during the simulation.if a delay is seen before the initial statement ,then that statement is executed <delay> time units after the simulation.

Always :unlike the above statement ,the always block is excuted all time during the simulation in the form of a loop.this statement is always associated with a sensitivity list or a delay.

Procedural Assignments:

Blocking Assignments :these statemnets are executed in the order they are specified in a sequential block.these statements will not block execution of statements that follow in a parallel block.the “=” operator is used to specify blocking assignments.

Non blocking statements :this is represented by “<=”.these assignments allow scheduling of assignments without blocking execution of the other statements in the block.typically, these statements are executed last after all the blocking assignments in the block are executed.

Syntax

module <module_name> (<module_terminal_list>);

Module_terminal_list describes the I/O terminals of the module.

Instantiation of Module

Process of creating OBJECTS from Modules Duplication of Modules. Objects are called instances.

Operators

There are 3 types

• Unary [ a = ~ b ]
• Binary [ a = b && c ]
• ternary [ a = b ? c : d ]

Number Specification

<size>’<base_format> < number>.

Ex : 4′b1111 / This is a 4-bit binary number

Parameter

Used to define Constants in a module

Compiler Directives

‘define

this is similar to #define in c.

‘include similar to the include header files in c.

Port Declaration

Module Name,

Port List, Port Declarations [ Ports provide an interface for the module to communicate to the external environment ]

Example:

module SR_latch(Q, Qbar, Sbar, Rbar);

//Port Declaration

output Q, Qbar;

input Sbar, Rbar;

Formal Syntax Definition : if (<expression>) true_statement ; else false_statement;

Case:

nested if-else in a code will yield unwanted results and create problems.this can be avoided by using the CASE statement .

Syntax Definition : case (expression)

alternative1: statement1;

alternative2:statement 2;

default

endcase

the expression is compared to the alternatives in the block and the statement of the alternative th at matches is executed else it goes to default.

1. Red Hat

2. Ubuntu , I use this at home and it is very good. Installation is very smooth and easy

3.Knoppix

What is perl

Interpreted programming language or Scripting language.

Perl was first brought into being by Larry Wall circa 1987 as a general purpose Unix scripting language to make his programming work simpler. Although it has far surpassed his original creation, Larry Wall still oversees development of the core language, and the newest version, Perl 6

How to Install Perl

-If you are like me using UBUNTU you get it pre-installed with the OS. However if you are using Windos and want to install it, you can download the binaries from this site : http://www.perl.com/

How to know the version of perl installed

perl -v

Some real good sites

Operators :

Similar to C programming language,verilog provides the following operators .

Arithmetic , logical ,relational,bitwise,equality , shift,concatenation,replication ,and conditional.

Operator Type Operator Symbol Operation Performed Arithmetic * Multiply / Division + Add - Subtract % Modulus + Unary plus - Unary minus Logical ! Logical negation && Logical and || Logical or Relational > Greater than < Less than >= Greater than or equal <= Less than or equal Equality == Equality != inequality Reduction ~ Bitwise negation ~& nand | or ~| nor ^ xor ^~ xnor ~^ xnor Shift >> Right shift << Left shift Concatenation { } Concatenation Conditional ? conditional Example – a = b + c ; // That was very easy a = 1 << 5; // Hum let me think, ok shift ’1′ left by 5 positions. a = !b ; // Well does it invert b??? a = ~b ; // How many times do you want to assign to ‘a’, it could cause multiple-drivers.

How to define an Array :

How to use an Array :

#!/usr/bin/perl
$name=”John Rob”;
print(“Hello,$name\n”);

$age=”20″;
print “$age+8\n”;

$s=”robert.ford”;
$a=”robert”;
print”$s,$a\n”;

@b=(“choclate”,”cake”,”pizza”);
print”@b\n”;
print”$#b\n”;

$firstname=”John”;
$middlename=”Robert”;
$lastname=”Coby”;
$wholename=(“$firstname”.”$middlename”.”$lastname”);
print”$wholename\n”;

$d=5;
$e=7;
$f=”$d+$e”;
if($f>0)
{
print”positive value “;
}
if($f<0)
{
print”negative value”;
}