Mehraj Shaikh: Your Tutoring Companion

Answer

Ans: A return keyword is used to transfer control from a function back to the calling function.

Syntax: return value;

Example:

#include <stdio.h>

int main()

{

int k = 0;

k = fun();

printf("\n Value of k returned from function : %d \n", k);

return 0;

}

int fun()

{

return 10;

}

 

Explaination: In above example fun() returns value 10 and this value is assigned to variable k in main(). Also main() returns value 0 (indicating successful execution) to operating system.

 

 

Answer

Answer: Each time when you allocate memory at run time using malloc() or calloc(), the memory get allocated fom heap area. It is necessary to free the memory which is allocated dynamically at run time to avoid memory leaks. The free() function is used to free the memory which is allocated previously using malloc() or calloc().

Syntax: free(mem_ptr);

Here mem_ptr is a pointer to memory allocated using malloc() or calloc().

Example: 

int *p = (int *)malloc(sizeof(int));

free(p);

 

 

Answer

=> Process 1. Each process provides the resources needed to execute a program.

2. A process has a virtual address space, executable code, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, and at least one thread of execution.

3. Each process is started with a single thread, often called the primary thread, but it can create additional threads from any of its threads.

=> Thread 1. A thread is an entity within a process that can be scheduled for execution.

2. All threads of a process share its virtual address space and system resources.

3. Each thread maintains exception handlers, a scheduling priority, thread local storage, a unique thread identifier, and a set of structures the system will use to save the thread context until it is scheduled.

4. The thread context includes the thread's set of machine registers, the kernel stack, a thread environment block, and a user stack in the address space of the thread's process.

Answer

Data abstraction means providing essential information to the outside world by hiding background or inner  details.

Example: We use gmail to send and receive mails without worrying actually how it works internally.

 

Answer

=> HINSTANCE : A handle to an instance. This is the base address of the module in memory.

=> HWND : A handle to window.

Answer

DDL COMMANDS:

1. CREATE TABLE

2. ALTER TABLE

3. DROP TABLE

DML COMMANDS

1. SELECT

2. INSERT INTO

3. UPDATE SET

4. DELETE

Answer

Answer: Imagine every account on Internet as a unique lock and it needs an unique key to open it. And here passwords work as unique keys for their unique locks. The locks (user accounts) protect data of authorized user from other unauthorized users. The authorized user then use unique key (password) to open his/her account. Hence authorized user keeps his/her password more complex to avoid intrusion from other users. The case-sensitiveness of passwords provide more ways to create complex passwords. 

Answer

RAM: While running any application, it needs to be stored somewhere temporarily so that the processor can access it at fast speed and process it. This place is RAM. While processing, processor frequently accesses and stores the data of application in RAM. Hence RAM's data is not fixed and can be altered or removed by processor as and when required. RAM is called random access memory, this is because the processor can store and retrieve application's data to and from random places of RAM at fast speed.

ROM: While starting up a computer, the OS needs the exact information (settings) about hardware on which it (OS) is going to be installed. This information (settings) is stored in ROM chip at the time of its creation by manufaturer. The instructions stored in ROM can only be read but can not be modified.