Tool Command Language- Lecture 9 (files)

In this lecture we will see how to read file from disk
The general format is as 

open file _name access permission 

access is the access mode

r.... open the file for reading . The file must b present.
r+...open a file for reading and writing.
w.. open the file for writing. create the file if it is not present.
w+.. open file for reading and writing.. create if not present.
a.. open file for writing . it must be present their.
a+.. open file for writing and create it if not present their.

permission :

permission is an integer to use  to set the file access permissions

close fileID:

closes the file that has been already created.

gets fileID varnamee:

reads a line from fileID and discards the terminating newline.

puts ? -nonewline? fileID string

writes in file.

Examples:

i have a file abc.text in this location \hoome\masroor.

a:

set ns

open \home\masroor\abc  r 

returns file3 which is file id

now i will use this id to close file

close file3

b:

open /home/masroor/abc w+

puts file4 "i hate this "

close file4

Tool Command Language- Lecture 8 ( search list)

Use of lsearch , lindex and lsort 
a)- lsearch

syntax.
set list {{item1} [item2}...}
set variable [lsearch  $list  item]
it will return index of item. Remember it starts from 0.
Example:

set p {{java 1991} {c 1987} {python 2000} {tcl 2005}} 
set x [lsearch $p "python 2000"]

puts $x 

out put : 2
Note: if output is -1 then the searched value is not present in list.

b) - lindex

syntax.
set list {{item1} [item2}...}
puts [lindex  $list  index(number)]
it will return value at index in list .

Example:

set p {{java 1991} {c 1987} {python 2000} {tcl 2005}} 
puts  [lindex $p 3]
out put : tcl 2005

c)-lsort
syntax.
set list {{item1} [item2}...}
lsort $list
Example:

set p {{java 1991} {c 1987} {python 2000} {tcl 2005}} 
lsort  $p
out put : {c 1987} {java 1991} {python 2000} {tcl 2005}

Tool Command Language - lecture 7 - Functions

The syntax of function or procedure in tcl is as

                
proc function_name { arguments } {

             body 

             return 

    } 

    Example
 proc add { a b } {

 return [expr $a + $b ]

  }

 set c [add 3 2 ]

 out put  5

 Here we have declared a function or most appropriate a  procedure  named as add, with arguments as a,b. Later we set a variable c and  we call the above function with two arguments. In return we obtain  sum of  these two arguments and that is assigned to c . 

Tool Command Language- Lecture 6 ( "for" loop )

For Loop:
The Syntax of "For" loop in Tcl is as
for {set variable value } {text condition }{ change value}{
body of loop 
}
Example :

for {set x 0 } { $x < 5 } {incr x} { 
puts " value of x : $x " 
}
Out Put:
value of x : 0
value of x : 1
value of x : 2
value of x : 3
value of x : 4

Create a Frame In java

import javax.swing.*;   
// swing class is placed in the javax.swing package
public class Main
{
    public static void main(String[] args)
{
EmpetyFrame f = new EmpetyFrame();
// we create a sub class wd class name EmpetyFrame
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// exit upon close event operation
   f.setVisible(true); 
// to show the frame main method calls setvisible method
}
}
class EmpetyFrame extends JFrame
{
public EmpetyFrame( ) // constructor sets size
{
setSize(default_width,default_height);
}
public static final int default_width = 300;
public static final int default_height = 300;
}

Tool command Language - lecture 5. (looping )

While loop:
The syntax of while loop in tcl is as
while {text condition } {
 body of loop
}  
 Example :
 set x 3
 while {$x <6} {
 incr  x 
 puts $x 
 }
                         
here the condition is ist checked and then inside loop value of x is increment by 1. when value of x becomes 6, then condition becomes false and the loop terminates.                

Tool Command language -Lecture 4(Use of Switch)

The use of Switch replaces multiple if-else. The syntax is as 
  
switch string pattern 1 body 1 pattern 2 body 2 ... pattern n body n
                                    or
switch string {pattern 1 body 1 pattern 2 body 2... pattern n body n}
example :

set x one
switch $x "ONE" "puts ONE=1" "two" "puts 2"
           or           
set c hate  
switch  $c {
"love" {
puts "i hate u"
 }
"hate" {
 puts "i know"
        }
     }

Tool Command Language - lecture 4 (Decision making and branching )

1. if - else

The syntax of if-else in tcl is as.
if { statement 1 } {statement 2} else {statement 3}
example
set x 10
if { $x == 2 } {puts "hello } else { puts "bye" }
  will print bye
we can also write it like 
if { $x == 2 } {
puts "hello 
} else {
 puts "bye" 
 }

Tool command Language - Lecture 3 ( Operators )

Operators in tcl are same as in other languages like c, c++.

Tcl supports following operators. 

        

  Arithmetic Operators (+, - , *, /,%)

 Relational Operators(==, !=, < , > , >=)

 Bitwise Operators(&,|,^)

 Ternary Operators(?:)

 Logical Operators(&&, || , !)

Here if we have two variables say x and y

   we write in tcl command prompt 

       set x 10

       set y 12

 puts c [expr $x +$y] will print c as 22. 

similarly  we can use relational operators in following manner

                while{$x < 13 } {  

                  incr x  

                  puts $ y

              }

   

  #Remember syntax.

For Ternary operator we have like c as 

      expression 1 ? expression 2 : expression 3.

if after evaluating  expression 1 , it is true then expression 2 will be evaluated. example

  set x 3

set y [expr ($x>4)?"x is greater than 4":"x is less than 4"]

will print " x is less than 4"

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Tool Command language (Tcl) .. Second lecture ( lists )

Lists

List is nothing but a group of elements. A group of words either using double quotes or curly braces

set x { red green blue }

    Here we have put three variables in list .

puts [lindex $x 2 ]

      Here we will get print blue.

  

Difference between 32 bits and 64 bits os.

The main difference is that a 32 bit os/processor can process 2^32 addresses and at a time can access 32 bits from memory. Here data handle/processed(data being processed internally )  by cpu is of width 32 bits.

Tool Command language (Tcl) .. First lecture ( variable declaration )

Variable Declaration 

  In c prog language  when we  declare some variable , we write 
  int x = 3;

  But in Tcl we write
  set x 3;
         "here it is stored as string"
  No need to declare just assign a value to variable. This  statement     will create a variable name x and store it as string.
          Now if we write
puts [expr $x + 5] #  we can also use (put)
      here x is automatically converted into int.
 Now to print x we will write


puts $x .. Answer will be 8 ( as expr above does addition operation)