What is Valid / Invalid Bits?

When a page is accessed, if the valid/invalid bit is set to valid, then the page is simply accessed in main memory via the logical address entry in the table. If the page is not contained in physical memory, then a page fault is generated. This causes the program to try and load the page into memory. The system first checks if the requested address is valid. If not, then the process is terminated. If the address is valid, then the system checks for free frames. If a free frame is found, then the system loads the requested data from the disk and places it in the free frame. The valid/invalid bit is set to valid in the paging table, the logical address is set to the previously free frame, and the program can continue executing. If no free frames are present, then the system must swap out a currently used frame and place the requested data in the frame. The system, an algorithm such as LRU, MRU, etc. to determine which page to swap out. The system swaps out the old page, loads in the new page and then returns control to the process.

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Recursive Function in C programming

If a statement within the body of a function calls the same function, the function is called recursive function. Actually, recursion is a process by which a function calls itself repeatedly until some specified condition has been satisfied. This process is used for repetitive computations in which each action is stated in term of previous result. Many iterative or repetitive problems can be written in this form. To solve a problem using recursive method, two conditions must be satisfied. They are: 1) Problem could be written or defined in term of its previous result. 2) Problem statement must include a stopping condition. /* An example of recursive function to calculate factorial of a number.*/ #include<stdio.h> #include<conio.h...

Passing arrays to functions in C programming

Like any other variables, we can also pass entire array to a function. An array name can be named as an argument for the prototype declaration and in function header. When we call the function no need to subscript or square brackets. When we pass array that pass as a call by reference because the array name is address for that array. /* Program to illustrate passing array to function */ #include<stdio.h> void display(int) ; /* function prototype */ main( ) { int num[5] = {100, 20, 40, 15, 33, i ; clrscr( ) ; printf (“\n The content of array is \n”) ; for (i=0; i<5; i++) display (num[i]) ; /*Pass array element fo fun */ getch{ } ; } void display(int n) { printf (“\t%d”, n ) ; } Output: The content of array is 100 20 40 15 3 /* Program to read 10 numbers from keyboard to store these num into array and then c...

Object Oriented Programming

Object Oriented Programming Programming paradigm that represents the concept of "objects" that have data fields (attributes that describe the object) and associated procedures known as methods Programming methodology based on objects, instead of just functions and procedures Focuses on data rather than process As individual objects can be modified without affecting other aspects of the program, it is easier for programmers to structure and organize software programs Easier to update and change programs written in object-oriented languages Simula was the first object oriented programming language Eg: C++, Java, etc. Features of OOPS Objects Referred as instance of class Basic run-time entities in an object-oriented system a person, a place, a bank account, a table of data, etc can be an object They occupy space in memory that keeps its state Each object contains data and code to manipulate the data Classes Blue print or prototype which ...

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