/*
2. Write the simulation program to implement demand paging and show the page scheduling and total number of page faults for the following given page reference string. Give input n as the number of memory frames.

Reference String: 3, 4, 5, 6, 3, 4, 7, 3, 4, 5, 6, 7, 2, 4, 6
*/

#include <stdio.h>
#include<stdlib.h>

struct fnode
{
    int pno;
}frames[5];

int pfct=0, i, n, pno, p, len=15,flag=0;
int ref_str[]={3, 4, 5, 6, 3, 4, 7, 3, 4, 5, 6, 7, 2, 4, 6};

int page_found(int pno)
{
    for (i=0;i<n;i++)
     if(frames[i].pno==pno)
        return i;
        return 0;
    
}

int main()
{
    printf("\nEnter no. of frames: ");
    scanf("%d",&n);
    printf("len:%d", len);
    for(i=0;i<n;i++)
    frames[i].pno=-1;
    printf("\nPage No  Frames   Page_Fault   PFCT");
    printf("\n------------------------------------\n");
    
    for(p=0;p<len;p++)
    {
      pno=ref_str[p];
      flag=0;
      if(page_found(pno)==0)
      {
         frames[pfct%n].pno=pno;
         pfct++;
         flag=1;
      }
     printf("\n%5d\t", pno);
    for(i=0;i<n;i++)
    printf("%d ",frames[i]);
    
    if(flag==1)
    printf("\tY");
    else
    printf("\tN");
    printf("\t%d", pfct);
    }
    printf("\n--------------------------------");
    printf("\n Total No. of Page Fault : %d", pfct);
 
 
    return 0;
}

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}