C Program to Check Whether a Given Number is Even or Odd

C and C++ programs to check whether a given number is Odd or even

C Program

#include<stdio.h>
void main()
{
int n;
printf("Enter an integer\n");
scanf("%d",&n);
if ( n%2 == 0 )
printf("Even");
else
printf("Odd");
}

Spiral Matrix Program in C - Zoho Interview Question - C Program to Read a Matrix in Spiral Order

A spiral matrix is a matrix (two dimensional array) in which the elements are stored in spiral manner. The order of accessing elements in the spiral matrix resembles a spiral. Actually it is a normal NxN two dimensional array. But instead of accessing elements row-wise or column-wise, we access them in spiral order. i.e, in a 3x3 matrix the order of retrieval of elements is spiral order is as follows:

(0,0)  (0,1)   (0,2)  (1,2)   (2,2)   (2,1)   (2,0)   (1,0)   (1,1)

The following picture shows a 4x4 spiral matrix:

A 4x4 Spiral matrix

Zoho, an IT company, asked an interview question which was to write a program to read a matrix spirally. In this post, we will answer this interview question  by zoho corporation. The only difference between spiral matrix and normal matrix is the order in which we store elements to matrix or access elements in matrix. The following is the C program to read a spiral matrix.

#include<stdio.h>
void main()
{
int a[10][10],o,cellcount,cc=0,c=0,i=0,j=0,g=1;
printf("\nEnter the order of spiral matrix: ");
scanf("%d",&o);
cellcount=o;
printf("\nEnter the elements:\n");
while(c<o*o)
    {
    cc=0;
    for(;cc<cellcount;j=j+g,cc++)
        scanf("%d",&a[i][j]);
    j=j-g;
    c+=cc;
    cc=0;
    i=i+g;
    cellcount--;
    if(c>=o*o)
        break;
    for(;cc<cellcount;i=i+g,cc++)
        scanf("%d",&a[i][j]);
    c+=cc;
    i=i-g;
    j=j-g;
    g*=-1;
    }
printf("\nThe spiral matrix is:");
for(i=0;i<o;i++)
    {
    printf("\n");
    for(j=0;j<o;j++)
        printf("%d\t",a[i][j]);
    }
}

The above program reads the matrix in spiral fashion and the displays the matrix in normal way. You can use this code not only to read and store the elements in matrix spirally but also to access the elements in the matrix in spiral order.

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C Program to Simulate Round Robin CPU Sceduling Algorithm

The round robin CPU scheduling algorithm is simulated using C program. The time slice or time quantum is read from the user.

Program:

#include<stdio.h>
struct process{



int burst,wait,comp,f;
}p[20]={0,0};
int main(){
int
n,i,j,totalwait=0,totalturn=0,quantum,flag=1,
time=0;
printf("\nEnter The No Of Process
:");
scanf("%d",&n);
printf("\nEnter The Quantum time (in ms)
:");
scanf("%d",&quantum);
for(i=0;i<n;i++){
printf("Enter The Burst Time (in ms) For
Process #%2d :",i+1);
scanf("%d",&p[i].burst);
p[i].f=1;
}
printf("\nOrder Of Execution \n");
printf("\nProcess \tStarting\tEnding\tRemaining");
printf("\n\tTime \tTime\tTime");
while(flag==1){
flag=0;
for(i=0;i<n;i++){
if(p[i].f==1){
flag=1;
j=quantum;
if((p[i].burst-p[i].comp)>quantum){
p[i].comp+=quantum;
}
else{
p[i].wait=time-p[i].comp;
j=p[i].burst-p[i].comp;
p[i].comp=p[i].burst;
p[i].f=0;
}
printf("\nprocess # %-3d %-10d %-10d %-10d",i+1,time,time+j,p[i].burst-
p[i].comp);
time+=j;
}}}
printf("\n\n------------------");
printf("\nProcess \t Waiting Time  TurnAround Time ");
for(i=0;i<n;i++){
printf("\nProcess # %-12d%-15d%-15d",i+1,p[i].wait,p[i].wait+p[i].burst);
totalwait=totalwait+p[i].wait;
totalturn=totalturn+p[i].wait+p[i].burst;
}
printf("\n\nAverage\n------------------");
printf("\nWaiting Time : %f ms",totalwait/(float)n);
printf("\nTurnAround Time : %f ms\n\n",totalturn/(float)n);
return 0;
}

C Program to Simulate the ls Command in Linux Operating system

This is a c program to do Simulation of ls Command in linux. The ls command lists all the contents of the directory including filse and sub-directories. The following c program in simulates the ls command.

#include<stdio.h>
#include<dirent.h>
main()
{
char dirname[10];
DIR*p;
struct dirent *d;
printf("Enter directory name\n");
scanf("%s",dirname);
p=opendir(dirname);
if(p==NULL)
  {
  perror("Cannot find directory");
  exit(-1);
  }
while(d=readdir(p))
  printf("%s\n",d->d_name);
}

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C Program to Simulate grep Command in Linux

This post contains C program to simulate grep command in Linux or Unix operating systems

Simulation of  grep command in Linux

#include<stdio.h>
#include<string.h>
void main()
{
char fn[10],pat[10],temp[200];
FILE *fp;
printf("Enter file name\n");
scanf("%s",fn);
printf("Enter pattern to be searched\n");
scanf("%s",pat);
fp=fopen(fn,"r");
while(!feof(fp))
{
fgets(temp,1000,fp);
if(strstr(temp,pat))
  printf("%s",temp);
}
fclose(fp);
}

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C Program to Simulate rmdir Command or Delete Directory
C Program to Open, Read and Write Files
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How to Use Exit System Call
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C Program to Remove (Delete) a Directory using LINUX System Calls

This is a C program to delete  or remove a directory using the system calls in Linux or Unix operating systems. The program make use of the remove() system call in Linux.

#include<stdio.h>
#include<fcntl.h>
main()
{



char fn[10];
printf("Enter source filename\n");
scanf("%s",fn);
if(remove(fn)==0)
printf("File removed\n");
else
printf("File cannot be removed\n");
}

C Program to open, read and write files and perform file copy operation usingSystem Calls in UNIX

Write a program to open, read and write files and perform file copy operation. This program show how to open, read, write and copy files using Linux or Unix system calls like open(), read() and write().

#include<stdio.h>
#include<fcntl.h>
main()
{


char buff[1000],fn1[10],fn2[10];
int fd1,fd2,n;
printf("Enter source filename\n");
scanf("%s",fn1);
printf("Enter destination file name\n");
scanf("%s",fn2);
fd1=open(fn1,O_RDONLY);
n=read(fd1,buff,1000);
fd2=open(fn2,O_CREAT|O_WRONLY);
n=write(fd2,buff,n);
close(fd1);
close(fd2);
}

C Program to Open, Read and Write a file using System Calls

This is a C program to open , read and write files using system calls in Linux (UNIX) operating systems. The system calls open(), read() and write() are used in the C program to open, read and write files in Unix/Linux operating systems.

#include<stdio.h>
#include<fcntl.h>
main()
{


char buff[100],fn[10];
int fd,n;
printf("Enter file name\n");
scanf("%s",fn);
fd=open(fn,O_RDONLY);
n=read(fd,buff,100);
n=write(1,buff,n);
close(fd);
}

Using System calls in C Program to rename a Directory in Linux

C Program to rename a directory in Unix or Linux operating systems using system call rename().

#include<stdio.h>
main()
{

char s[10],d[10];
printf("Enter source Dir Name:\n");
scanf("%s",s);
printf("Enter New Dir Name:\n");
scanf("%s",d);
if(rename(s,d)==-1)
perror("Can't be changed\n");
else
printf("%s is changed to %s\n\n",s,d);
}

How to Create process and display Process ID (pid) of Both Parent and Child

This program shows how to create process and display Process ID (pid) of Both Parent and Child processes. The process is created using the fork system call in UNIX (Linux) operating systems.

#include<stdio.h>
#include<dirent.h>
main(int argc,char **argv)
{

int pid,i;
for(i=0;i<atoi(argv[1]);i++)
{
pid=fork();
if(pid==0)
{
printf("child process id %d Parent process
id %d\n",getpid(),getppid());
}}}

How to use exit() System call

C program to show how to use exit system call. The function exit() is used to exit from a process (or to terminate a process). This works both in Linux or UNIX and Windows operating systems.

#include<stdio.h>
main()
{

int pid;
pid=fork();
printf("%d\n",pid);
if(pid<0)
{
perror("Child can't be executed\n");
exit(-1);
}
else
{
printf("Child created\n");
exit(0);
}
}

C Program To Implement Circular Linked List

C Program to implement circular linked list.

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

struct node
    {
    int info;
    struct node *link;
    }*last;
void create_list(int num);
void addatbeg(int num);
void addafter(int num,int pos);
void del(int num);
void display();
void main()
    {
    int choice,n,m,po,i;
    last=NULL;
    while(1)
        {
        printf("1.Create List\n");
        printf("2.Add at begining\n");
        printf("3.Add after \n");

printf("4.Delete\n");

        printf("5.Display\n");
        printf("6.Quit\n");
        printf("Enter your choice : ");
        scanf("%d",&choice);

switch(choice)
           {
           case 1: printf("How many nodes you want : ");
                   scanf("%d",&n);
                   for(i=0; i < n;i++)
                      {
                      printf("Enter the element : ");
                      scanf("%d",&m);
                      create_list(m);
                      }
                   break;
           case 2: printf("Enter the element : ");
                   scanf("%d",&m);
                   addatbeg(m);
                   break;
           case 3: printf("Enter the element : ");
                   scanf("%d",&m);
                   printf("nter the position after which this element is inserted: ");
                   scanf("%d",&po);
                   addafter(m,po);
                   break;
           case 4: if(last == NULL)
                        {
                        printf("List underflow\n");
                        continue;
                        }
                   printf("Enter the number for deletion : ");
                   scanf("%d",&m);
                   del(m);
         break;
           case 5: display();
     break;
           case 6: exit(0);
           default:printf("Wrong choice\n");
           }
       }
   }
void create_list(int num)
   {
   struct node *temp;
   temp=(node*)malloc(sizeof(struct node));
   temp->info = num;
   if(last == NULL)
       {
       last = temp;
       temp->link = last;
       }
   else
       {
       temp->link = last->link;
       last->link = temp;
       last = temp;
       }
   }

void addatbeg(int num)
    {
    struct node *temp;
    temp =(node*)malloc(sizeof(struct node));
    temp->info = num;
    temp->link = last->link;
    last->link = temp;
    }
void addafter(int num,int pos)
    {
    struct node
    *temp,*q;
    int i;
    q = last->link;
    for(i=0;i<pos-1;i++)
       {
       q = q->link;
       if(q==last->link)
           {
    printf("There are less than %d elements\n",pos);
           return;
    }
       }
    temp =(node*)malloc(sizeof(struct node) );
    temp->link = q->link;
    temp->info = num;
    q->link = temp;
    if(q==last)  //Element inserted at the end
        last=temp;
    }//End of addafter()

void del(int num)
    {
    struct node *temp,*q;
    if( last->link == last && last->info == num)  //Only one element
        {
        temp=last;
        last = NULL;
        free(temp);
        return;
 }
    q = last->link;
    if(q->info == num)
        {
 temp = q;
        last->link = q->link;
        free(temp);
        return;
 }
    while(q->link !=last)
        {
        if(q->link->info==num) //Element deleted in between
           {
           temp = q->link;
           q->link = temp->link;
           free(temp);
           printf("%d deleted\n",num);
           return;
           }
       q = q->link;
       }
   if(q->link->info==num) //Last element deleted q->link=last
       {
       temp = q->link;
       q->link = last->link;
       free(temp);
       last = q;
       return;
       }
   printf("Element %d not found\n",num);
   }

void display()
   {
   struct node *q;
   if(last == NULL)
      {
      printf("List is empty\n");
      return;
      }
   q = last->link;
   printf("List is :\n");
   while(q != last)
      {
      printf("%d ", q->info);
      q = q->link;
      }
   printf("%d\n",last->info);
   }

Program to Check Armstrong Number

An Armstrong number is a positive integer for which the sum of 'n'th power of its digits is equal to the number itself where n is the number of digits in the number. This is a c program to check whether a given number is an Armstrong number or not. For example, 153 is a 3 digit Armstrong number because 1³+5³+3³=153.

# include <stdio.h>
# include <conio.h>
# include <math.h>
void main ()
{
int a,b=0,sum=0;
long int n;
printf("Enter the number to check\n ");
scanf("%i",&n);
if(n<1)
{
printf ("\nThe number should be greater than 0");
}
else
{
a=n;
//counting the digits
while (a>0)
  {
  a=a/10;
  b++;
  }
a=n;
//adding up bth power of digits
while(a>0)
  {
  sum=sum+pow(( a%10) ,b);
  a=a/10;
  }
if(sum==n)
  printf ("\nThe number is an ARMSTRONG number");
else
  printf ("\nThe number is NOT an ARMSTRONG number");
}
getch();
}

C Program to Sort a Matrix Column wise using Pointers

This is a c program to sort a mxn matrix column wise in ascending order using pointers. To sort column wise in descending order, just replace the '>' symbol in the comparing line of code into '<'. That part of the code is marked with a comment 'comparison'.

#include<stdio.h>
main()
{
int a[7][7],i,j,k,m,n,temp;

//reading
printf("enter number of rows of matrix\n");
scanf("%i",&m);
printf("enter number of columns of matrix\n");
scanf("%i",&n);
printf("enter the elements\n");
for(i=0;i<m;i++)
{
for(j=0;j<n;j++)
scanf("%d",&a[i][j]);
}
//displaying
printf("the matrix you entered:\n");
for(i=0;i<m;i++)
{
printf("\n");
for(j=0;j<n;j++)
{
printf("%4d",*(*(a+i)+j));
}
}


//sorting
for(i=0;i<n;i++)
{
for(k=0;k<m-1;k++)
{
for(j=0;j<m-k-1;j++)
{
//comparison
if( *(*(a+j)+i)> *(*(a+(j+1))+i)) 
{
temp=*(*(a+j)+i);
*(*(a+j)+i)=*(*(a+(j+1))+i);
*(*(a+(j+1))+i)=temp;
}
}
}
}
//displaying
printf("\nSorted Matrix:\n");
for(i=0;i<m;i++)
{
printf("\n");
for(j=0;j<n;j++)
{
printf("%4d",*(*(a+i)+j));
}
}
}

Determinant of Matrix Program - Program to Find Determinant of Matrix

In this post i am sharing a C program to calculate determinant of matrices. Determinant exists only for square matrix. Here i have wrote a c program to find determinant of matrices of order less than or equal to 3.

#include<stdio.h>

void main()
{
int a[10][10],i,m,j;
int det=0;
printf("\nEnter the order of matrix:\n ");
scanf("%i",&m);
printf("\nenter elements\n");
for(i=0;i<m;i++)
 {
 for(j=0;j<m;j++)
  scanf("%d",&a[i][j]);
 }
printf("\nThe matrix is\n");
for(i=0;i<m;i++)
 {
 printf("\n");
 for(j=0;j<m;j++)
  printf("%3d",a[i][j]);
 }
printf("\nthe transpose is\n");
for(i=0;i<m;i++)
{
for(j=0;j<m;j++)
printf("%3i",a[j][i]);
printf("\n");
}
if(m==1)
{
det=a[0][0];
printf("det=%i",det);
}
else if(m==2)
{
int k=1,l=1;
for(i=0;i<2;i++)
for(j=0;j<2;j++)
{
if(i==j)
k*=a[i][j];
else
l*=a[i][j];
}
printf("\ndeterminant=%i",k-l);
}
else if(m==3)
{
for(i=0;i<3;i++)
det=det+(a[0][i]*(a[1][(i+1)%3]*a[2][(i+2)%3]-a[1][(i+2)%3]*a[2][(i+1)%3])); 
printf("\nDeterminant of matrix is: %d",det);
}
else
printf("This program can't calculate determinant of matrix of order greater than 3");
}