What is the difference between numbered list and bulleted list in ms word ?

In bulleted lists, each paragraph begins with a bullet character. In numbered lists, each paragraph begins with an expression that includes a number or letter and a separator such as a period or parenthesis. The numbers in a numbered list are updated automatically when you add or remove paragraphs in the list.

Eg:

• These
• are
• bullets

In a numbered list this is replaced by a number, in sequential order.

Eg:

1. This

2. Himmat

Query in MS Access

query is a request for data results, and for action on data. You can use a query to answer a simple question, to perform calculations, to combine data from different tables, or even to add, change, or delete table data.

• As tables grow in size they can have hundreds of thousands of records, which makes it impossible for the user to pick out specific records from that table.

• With a query you can apply a filter to the table's data, so that you only get the information that you want.

• Queries that you use to retrieve data from a table or to make calculations are called select queries.

• Queries that add, change, or delete data are called action queries.

• You can also use a query to supply data for a form or report.

• In a well-designed database, the data that you want to present by using a form or report is often located in several different tables.

• The tricky part of queries is that you must understand how to construct one before you can actually use them.

Create Select Query

If you want to review data from only certain fields in a table, or review data from multiple tables simultaneously or maybe just see the databased on certain criteria, you can use the Select query. Let us now look into a simple example in which we will create a simple query which will retrieve information from tblEmployees table. Open the database and click on the Create tab.

how to put comments in xml

This chapter explains how comments work in XML documents. XML comments are similar to HTML comments. The comments are added as notes or lines for understanding the purpose of an XML code.

Comments can be used to include related links, information, and terms. They are visible only in the source code; not in the XML code. Comments may appear anywhere in XML code.

Syntax

XML comment has the following syntax −

<!--Your comment-->

A comment starts with <!-- and ends with -->. You can add textual notes as comments between the characters. You must not nest one comment inside the other.

Example

Following example demonstrates the use of comments in XML document −

<?xml version = "1.0" encoding = "UTF-8" ?>

<!--Students grades are uploaded by months-->

<class_list>

   <student>

      <name> RATHORE </name>

      <grade>A</grade>

   </student>

</class_list>

Any text between <!-- and --> characters is considered as a comment.

XML Comments Rules

Following rules should be followed for XML comments −

Comments cannot appear before XML declaration.

Comments may appear anywhere in a document.

Comments must not appear within attribute values.

Comments cannot be nested inside the other comments.

What is thread ?

 A thread is a flow of execution through the process code, with its own program counter that keeps track of which instruction to execute next, system registers which hold its current working variables, and a stack which contains the execution history.

A thread shares with its peer threads few information like code segment, data segment and open files. When one thread alters a code segment memory item, all other threads see that.

A thread is also called a lightweight process. Threads provide a way to improve application performance through parallelism. Threads represent a software approach to improving performance of operating system by reducing the overhead thread is equivalent to a classical process.

Each thread belongs to exactly one process and no thread can exist outside a process. Each thread represents a separate flow of control. Threads have been successfully used in implementing network servers and web server. They also provide a suitable foundation for parallel execution of applications on shared memory multiprocessors. The following figure shows the working of a single-threaded and a multithreaded process.

Difference between Process and Thread

S.N.	Process	Thread
1	Process is heavy weight or resource intensive.	Thread is light weight, taking lesser resources than a process.
2	Process switching needs interaction with operating system.	Thread switching does not need to interact with operating system.
3	In multiple processing environments, each process executes the same code but has its own memory and file resources.	All threads can share same set of open files, child processes.
4	If one process is blocked, then no other process can execute until the first process is unblocked.	While one thread is blocked and waiting, a second thread in the same task can run.
5	Multiple processes without using threads use more resources.	Multiple threaded processes use fewer resources.
6	In multiple processes each process operates independently of the others.	One thread can read, write or change another thread's data.

Advantages of Thread

• Threads minimize the context switching time.
• Use of threads provides concurrency within a process.
• Efficient communication.
• It is more economical to create and context switch threads.
• Threads allow utilization of multiprocessor architectures to a greater scale and efficiency.

Types of Thread

Threads are implemented in following two ways −

• User Level Threads − User managed threads.

• Kernel Level Threads − Operating System managed threads acting on kernel, an operating system core.

User Level Threads

In this case, the thread management kernel is not aware of the existence of threads. The thread library contains code for creating and destroying threads, for passing message and data between threads, for scheduling thread execution and for saving and restoring thread contexts. The application starts with a single thread.

Advantages

• Thread switching does not require Kernel mode privileges.
• User level thread can run on any operating system.
• Scheduling can be application specific in the user level thread.
• User level threads are fast to create and manage.

Disadvantages

• In a typical operating system, most system calls are blocking.
• Multithreaded application cannot take advantage of multiprocessing.

Kernel Level Threads

In this case, thread management is done by the Kernel. There is no thread management code in the application area. Kernel threads are supported directly by the operating system. Any application can be programmed to be multithreaded. All of the threads within an application are supported within a single process.

The Kernel maintains context information for the process as a whole and for individuals threads within the process. Scheduling by the Kernel is done on a thread basis. The Kernel performs thread creation, scheduling and management in Kernel space. Kernel threads are generally slower to create and manage than the user threads.

Advantages

• Kernel can simultaneously schedule multiple threads from the same process on multiple processes.
• If one thread in a process is blocked, the Kernel can schedule another thread of the same process.
• Kernel routines themselves can be multithreaded.

Disadvantages

• Kernel threads are generally slower to create and manage than the user threads.
• Transfer of control from one thread to another within the same process requires a mode switch to the Kernel.

Multithreading Models

Some operating system provide a combined user level thread and Kernel level thread facility. Solaris is a good example of this combined approach. In a combined system, multiple threads within the same application can run in parallel on multiple processors and a blocking system call need not block the entire process. Multithreading models are three types

• Many to many relationship.
• Many to one relationship.
• One to one relationship.

Many to Many Model

The many-to-many model multiplexes any number of user threads onto an equal or smaller number of kernel threads.

The following diagram shows the many-to-many threading model where 6 user level threads are multiplexing with 6 kernel level threads. In this model, developers can create as many user threads as necessary and the corresponding Kernel threads can run in parallel on a multiprocessor machine. This model provides the best accuracy on concurrency and when a thread performs a blocking system call, the kernel can schedule another thread for execution.

Many to One Model

Many-to-one model maps many user level threads to one Kernel-level thread. Thread management is done in user space by the thread library. When thread makes a blocking system call, the entire process will be blocked. Only one thread can access the Kernel at a time, so multiple threads are unable to run in parallel on multiprocessors.

If the user-level thread libraries are implemented in the operating system in such a way that the system does not support them, then the Kernel threads use the many-to-one relationship modes.

One to One Model

There is one-to-one relationship of user-level thread to the kernel-level thread. This model provides more concurrency than the many-to-one model. It also allows another thread to run when a thread makes a blocking system call. It supports multiple threads to execute in parallel on microprocessors.

Disadvantage of this model is that creating user thread requires the corresponding Kernel thread. OS/2, windows NT and windows 2000 use one to one relationship model.

Difference between User-Level & Kernel-Level Thread

S.N.	User-Level Threads	Kernel-Level Thread
1	User-level threads are faster to create and manage.	Kernel-level threads are slower to create and manage.
2	Implementation is by a thread library at the user level.	Operating system supports creation of Kernel threads.
3	User-level thread is generic and can run on any operating system.	Kernel-level thread is specific to the operating system.
4	Multi-threaded applications cannot take advantage of multiprocessing.	Kernel routines themselves can be multithreaded.

Difference Between Linker and Loader

 Difference Between Linker and Loader : 

 

S.No.	LINKER	LOADER
1	The main function of Linker is to generate executable files.	Whereas main objective of Loader is to load executable files to main memory.
2	The linker takes input of object code generated by compiler/assembler.	And the loader takes input of executable files generated by linker.
3	Linking can be defined as process of combining various pieces of codes and source code to obtain executable code.	Loading can be defined as process of loading executable codes to main memory for further execution.
4	Linkers are of 2 types: Linkage Editor and Dynamic Linker.	Loaders are of 4 types: Absolute, Relocating, Direct Linking, Bootstrap.
5	Another use of linker is to combine all object modules.	It helps in allocating the address to executable codes/files.
6	Linker is also responsible for arranging objects in program’s address space.	Loader is also responsible for adjusting references which are used within the program.