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If pointer also keeps the variable's address in it and at the same time we can get the variable's address using & sign, can't we do the same task pointer does by deriving the address of any variable? I mean if I don't declare it as pointer and use it as int ptr = &i; in 2nd code snippet and use it as normal variable, what would be the differences?

That code doesn't illustrate why pointers exist, or why they are useful.

C actually requires us to use pointers in the following cases:

Pointers also make dynamic data structures like trees and lists easy to implement, but they aren't required for it (unless you're using dynamic memory allocation in those structures).

Writing to a function's parameters

C passes all function arguments by value; the formal parameter in the function definition is a separate object in memory from the actual parameter in the function call, so any change to the formal parameter is not reflected in the actual parameter. For example, assume the following swap function:

This function exchanges the values in a and b. However, when we call the function as

the values of x and y won't be updated, because they are different objects than a and b. If we want to update x and y, we have to pass pointers to them:

and update the function definition as follows:

Instead of swapping the contents of a and b, we swap the contents of the objects that a and b point to. This crops up all the time - think about the scanf function, and how you have to use the & operator on scalar arguments.

Tracking dynamically allocated memory

The dynamic memory allocation functions malloc, calloc, and realloc all return pointers to dynamic memory buffers; there's no variable associated with that memory as such.

A pointer is the only way to track that memory.

The second argument, if present, specifies the file location to copy to (if absent, the location will be a tempfile with a generated name). The third argument, if present, is a hook function that will be called once on establishment of the network connection and once after each block read thereafter. The hook will be passed three arguments; a count of blocks transferred so far, a block size in bytes, and the total size of the file. The third argument may be -1 on older FTP servers which do not return a file size in response to a retrieval request.

If the url uses the http: scheme identifier, the optional data argument may be given to specify a POST request (normally the request type is GET). The data argument must in standard application/x-www-form-urlencoded format; see the urlencode() function below.

when it detects that the amount of data available was less than the expected amount (which is the size reported by a Content-Length header). This can occur, for example, when the download is interrupted.

The Content-Length is treated as a lower bound: if there’s more data to read, urlretrieve() reads more data, but if less data is available, it raises the exception.

You can still retrieve the downloaded data in this case, it is stored in the content attribute of the exception instance.

If no Content-Length header was supplied, urlretrieve() can not check the size of the data it has downloaded, and just returns it. In this case you just have to assume that the download was successful.

By the way, they're called arguments or parameters, not attributes.

In Angular, there are two types of linking functions:

Pre-linking Function The pre-linking function executes before the child elements are linked to the parent directive. It allows developers to perform tasks before Angular compiles and links the child elements.

Post-linking Function The post-linking function executes after the child elements are linked to the parent directive. It enables developers to interact with the DOM after Angular has finished linking the child elements.

Parameter Values: It is...

long int d; // 32 bits, range -2,147,483,648 to 2,147,483,647 (minimum requirement, can be higher on 64bit systems)