How Mobile Phones Work

Mobile Phones and Base Stations

master reset code for all samsung mobile phones

master reset code for all samsung phones 
this will delete all your data off your phone
this is the code *2767*3855#

How to protect yourself from android viruses and how to remove them!

How To Fix Water Damage iPhone 4 Or ANY Device! Repair HD Complete How T...

Water or liquid Damaged phone: Whats to do? How to recover phone? What i...

What you should do if your phone drops in water?
And how to recover phone?
What is physics underneath it?

One question that asked several times to me is that what's to do, when phone drop in water, tea, coffee or something similar or these things are poured onto the phone. Is this damage yours phone? You will shock to know that, water is a main component used in fabrication of these phones and its tiny components and ICs. So why these phone, damages with water? And, how will you recovered damaged phones?

In this video I will show you how the water damages the component on the board. And why Samsung is more resistive to this damage. The IC's on Samsung phone are sealed. And there is less probability of entering water underneath the IC. The BGA ICs are more sensitive to water. You will shock to know that these IC are cleaned with water before packaging. So why water create problem here. The problem is created by water itself. During fabrication De ionised water is taken whose conductivity is very low. But the water that we use in our home has sufficient conductivity. And when it stuck under these IC's, the BGA connects are shorted. This will damage the IC or the component attached to these IC's. In worse condition the water underneath boils due to power voltage across the BGA balls. And that expansion torn the IC's pin-outs from the board. So only drying the board, completed the recovery process. You have to take out all of the water underneath the ICs. This can't be done, either by putting phone in Rice or Tea, or by compressed air. Now there is one catch here, dry the board in your hand this will limit the temperature. Because excessive heat boils the water underneath the IC and thus create a pressure underneath IC, this will, either break IC or torn the contact pads on PCB. So go slowly. 

samsung s4 water damage dead

Samsung S4 Not Charging, Not Syncing, Repair - Fix

Samsung Galaxy S3 dead repair by changing EMMC [HD]

How to... ? Rework ... T-862++ Digital Infrared IRDA Soldering Station -...

How to... Reball ? - BGA Reballing Exercise for 50mm Chip of a Computer ...

SMD Removal using a Chip Quik kit

How To Remove IC | Mobile Phone Repairing

How To Remove IC | Mobile Phone Repairing

How Mobile Phone Works

How Mobile Phone Works

Samsung Galaxy S3 Vs Apple iPhone 5

Samsung Galaxy S3 Vs Apple iPhone 5

Mobile Phone Repairing - How to Repair Mobile Phone

Mobile Repair Tools and Components

Mobile Components

Measuring Tools

Software Installation for Nokia Mobile Flashing

Mobile Repairing Tools

Mobile Repairing Tools

Disassembling & Assembling of Mobile Phone

Video on Mobile Phone Disassembling and Assembling

Photos of National Conference on Research Issues in Soft Computing - NCRISC'14 - 20-September 2014

Unix Commands

Unix is a computer operating system. An operating system is the software that provides the interface between the hardware of a computer system and the applications programs that are used on it. Simply put, the operating system provides the link between the hardware of the computer and the user. Popular operating systems include DOS (used on PCs) and VM/CMS (used on mainframes, now becoming rare). Unix is available on a wide variety of computer systems, including personal computers, workstations, mainframes and supercomputers. It was developed for, and is particularly well-suited to, multi-user systems, but is now also run on 'stand-alone' machines.

Unix was first developed in the early 1970s at Bell Laboratories in the USA. It was originally developed as a system to be used by the staff in the laboratories, and it was principally intended to provide an operating system that people would enjoy using. It was designed for users who were largely computer scientists, which may explain some of the more arcane and apparently unfriendly features of Unix, such as the obscure sounding command names. AT&T (the owners of Bell Laboratories) made Unix available at nominal cost to academic users, with whom it became popular. This helped to create a market for Unix, at a time when technological changes had themselves created a need for a portable multi-user operating system. As a result Unix began to be adopted by non-academic users in the 1980's as it became commercially available. Several standards are now being worked out, and Unix is steadily becoming the standard operating system in many environments.

(Image Source)

Some Common Commands

• ls View a list of all files and folders in the current directory
• cd Change to a different directory
• pwd Display the path of your current directory
• cp Copy files
• cp -R Copying directories
• mv Move files and change filenames
• rm Removing files
• rmdir Removing directories
• mkdir Create new directories
• chmod Changing permissions on files
• man The manual pages
• quota -v View quota
• kill -9 pid Killing processes
• grep Search for patterns or words in files
• clear Clear the terminal
• diff Show the differences between two textfiles
• find Search for files

Following are the link for Unix Commands

• Basic Unix Commands
• Unix Commands - List
• Unix Commands - Categories
• Unix Commands
• Unix Concept & Commands
• Unix Commands with examples

MS DOS Internal & External Commands

DOS Commands are instructions to perform tasks on files and directories. They are case insensitive. And as you already know, file is the area where we store group of information or data, and collection of group of files is called a directory.  

The internal commands reside in COMMAND.COM, which loads into memory when the computer system is started; these commands do not reside on disk. The external commands are files that do reside on disk and have an extension of .COM, .EXE, or .BAT. Both command types are executed from the MS-DOS prompt.


For Detailed Internal and External Commands with Examples.Kindly refer the following link 

• Internal and External Commands
• DOS COMMANDS
• DOS COMMANDS - SYNTAX
• List of Commands
• DOS Manual - Commands

Under Creative Commons License: Attribution

Operating System Questions - BU Previous

File System Notes
_____________________________________________________

IV SEMESTER B.C.A EXAMINATION ,MAY 2007

OPERATING SYSTEM

TIME:3 HRS
MAX MARKS:80

SECTION-A
ANSWER ANY EIGHT OF THE FOLLOWING(MARKS:8*3=24)

1.DEFINE AN OPERATING SYSTEM .DIFFERENTIATE BETWEEN ON-LINE AND OFF-LINE OPERATIONS
2.EXPLAIN ANY THREE SERVICES PROVIDED BY THE OPERATING SYSTEM
3.WHAT IS PCB?EXPLAIN BRIEFLY
4.EXPLAIN THE DIFFERENT PROCESS SCHEDULERS
5.BRIEFLY EXPLAIN DEADLOCK RECOVERY
6.WHAT IS CONTEXT SWITCHING?
7.WHAT IS SEGMENTATION?EXPLAIN
8.EXPLAIN LINKED ALLOCATION METHOD FOR FILES
10.GIVE ANY THREE FEATURES OF UNIX OPERATING SYSTEM

SECTION-B
ANSWER NY FOUR OF THE FOLLOWING(4*14=56)
11.a)EXPLAIN DISTRIBUTED OPERATING SYSTEM ALONG WITH ITS ADVANTAGES
b)EXPLAIN SYSTEM CALLS

12a)EXPLAIN READER-WRITER PROBLEM
b)DISCUSS ANY TWO METHODS OF DEADLOCK PREVENTION

13a)EXPLAIN ANY 4 PROCESS SCHEDULING CRITERIA
b)EXPLAIN ROUND ROBIN SCHEDULING ALGORITHM WITH EXAMPLE

14.a)EXPLAIN DEMAND PAGING WITH ILLUSTRATIVE EXAMPLE
b)EXPLAIN FIFO PAGE REPLACEMENT ALGORITHM WITH AN EXAMPLE

15a)DISCUSS ANY TWO DISK SCHEDULING ALGORITHMS
b)EXPLAIN ANY ONE DIRECTORY STRUCTURE

16 WRITE SHORT NOTES ON
a)FREE SPACE MANAGEMENT
b)SEMAPHORES
c)COMPACTION

___________________________________________________

Bachelor of Computer Application (BCA), NOV - 2009

Operating Systems


1. ____________ contains the most frequently used functions in operating system.
a. Monitor   b. Sceduling   c. Nucleus   d. None of the above 

 
2. The function of 'Ref' in Linux is ____________.
a. Pointer to this modules symbol table
b. List of modules that use this module
c. Starting address of module
d. Current state of module 

3. ____________ character is used to access any file on the disk.
A. Back slash
b. Forward slash
c. $
d. Double slash 

4. In modern operating system, ____________ is used to restore file system incase of disk crashes and system failure.
a. MVS
b. FAT
c. NTFS
d. None of the above 

5. The number of process running simultaneously and competing for the CPU is known as ____________ of multiprogramming.
a. Ratio
b. Depth
c. Degree
d. None of the above 

6. After termination, the operating system is put to - state for a while before removing all its detail from memory.
a. New
b. Halt
c. Blocked
d. Ready 

7. ____________ fit reduces search time considerably.
a. First
b. Best
c. Quick
d. None of the above 

8. A page modified in main memory is called as ____________ page.
a. Modified
b. Dirty
c. Changed
d. Altered 

9. In ____________, a secondary server takes over in case of primary server failure.
a. Server shared disk
b. Server connected to disk
c. Passive stand by
d. Active stand by 

10. Caching is used in ____________ clusters.
a. Beowulf
b. Windows 2000
c. Sun
d. None of the above 
---------
11. a. Describe the services of operating system in detail.

Or

b. Write a note on client/server model. 

12. a. Explain about the Booting concept.

Or

b. Describe the usage of device driver. 

13. a. What is context switching? Explain.

Or

b. Describe the different process states of operating system. 

14. a. State the usage of variable partition.

Or

b. Explain the working of compaction. 

15. a. Categorize the different classes of client/server applications.

Or

b. Explain the concept of W2K cluster server design. 

----------------------------------------

16. a. Elucidate the working of Time sharing system with example.

Or

b. Sketch the architecture of UNIX in detail. 

17. a. Give the structure of operating system with a neat diagram.

Or

b. Discuss about
i. File mounting and
ii. Disk formatting 

18. a. What is a process? Explain.

Or

b. Comment on process state transition. 

19. a. Explain the concept of paging. Use any one method and explain how PMT's implemented.

Or

b. Discuss any 5 page replacement policies with example. 

20. a. Describe the concept of Remote procedure call.

Or

b. Discuss about clusters. 

----------------------------