## INDEX

### C questions and answer with explanation

1. PERFECT NUMBER.
void main()
{
int n,i=1,sum=0;
clrscr();
printf("\nEnter a number:-");
scanf("%d",&n);
while(i<n)
{
if(n%i==0)
sum=sum+i;
i++;
}
if(sum==n)
printf("\nThe no %d is a perfect number",i);
else
printf("\nThe no %d is not a perfect number",i);
getch();
}
2. ARMSTRONG NUMBER.
void main()
{
int num,r,sum=0,temp;
clrscr();
printf("\nEnter a number:-");
scanf("%d",&num);
temp=num;
while(num!=0)
{
r=num%10;
num=num/10;
sum=sum+(r*r*r);
}
if(sum==temp)
printf("\nThe number %d is an armstrong number",temp);
else
printf("\nThe number %d is not an armstrong number",temp);
getch();
3. STRONG NUMBER
void main()
{
int num,i,f,r,sum=0,temp;
clrscr();
printf("\nEnter a number");
scanf("%d",&num);
temp=num;
while(num)
{
i=1,f=1;
r=num%10;
while(i<=r)
{
f=f*i;
i++;
}
sum=sum+f;
num=num/10;
}
if(sum==temp)
printf("%d is a strong number",temp);
else
printf("%d is not a strong number",temp);
getch();
}
4. PRIME NUMBER.
void main()
{
int num,i,count=0;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
for(i=1;i<=num;i++)
{
if(num%i==0)
count++;
}
if(count==2)
printf("%d is a prime number",num);
else
printf("%d is not a prime number",num);
getch();
}
5. REVERSE A NUMBER
void main()
{
int num,sum=0,r;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
while(num)
{
r=num%10;
sum=sum*10+r;
num=num/10;
}
printf("\nReverse number=%d",sum);
getch();
}
6. SUM OF THE DIGITS OF A NUMBER
void main()
{
int num,sum=0,r;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
while(num)
{
r=num%10;
num=num/10;
sum=sum+r;
}
printf("sum=%d",sum);
getch();
}
7. PALINDROME NUMBER.
void main()
{
int num,r,sum=0,temp;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
temp=num;
while(num)
{
r=num%10;
num=num/10;
sum=sum*10+r;
}
if(temp==sum)
printf("\n%d is a palindrome",temp);
else
printf("\n%d is not a palindrome",temp);
getch();
}
8. G.C.D OF TWO NUMBERS
void main()
{
int n1,n2;
clrscr();
printf("\nEnter two numbers:");
scanf("%d %d",&n1,&n2);
while(n1!=n2)
{
if(n1>n2)
n1=n1-n2;
else
n2=n2-n1;
}
printf("\nGCD=%d",n1);
getch();
}
9. L.C.M OF TWO NUMBERS.
void main()
{
int n1,n2,x,y;
clrscr();
printf("\nEnter two numbers:");
scanf("%d %d",&n1,&n2);
x=n1,y=n2;
while(n1!=n2)
{
if(n1>n2)
n1=n1-n2;
else
n2=n2-n1;
}
printf("L.C.M=%d",x*y/n1);
getch();
}
10. SWAP TWO VARIABLES WITHOUT USING THIRD VARIABLE
void main()
{
int a,b;
clrscr();
printf("\nEnter two numbers:");
scanf("%d %d",&a,&b);
printf("\nBefore swapping a=%d b=%d",a,b);
a=a^b;
b=b^a;
a=a^b;
printf("\nAfter swapping a=%d b=%d",a,b);
getch();
}
11. FLOYD’S TRIANGLE
1
2 3
4 5 6
void main()
{
int i,j,r,k=1;
clrscr();
printf("\nEnter the range:");
scanf("%d",&r);
printf("\nFLOYD'S TRIANGLE\n\n");
for(i=1;i<=r;i++)
{
for(j=1;j<=i;j++,k++)
printf(" %d",k);
printf("\n");
}
getch();
}
12. PRIME FACTORS OF A NUMBER
void main()
{
int num,i=1,j,k;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
while(i<=num)
{
k=0;
if(num%i==0)
{
j=1;
while(j<=i)
{
if(i%j==0)
k++;
j++;
}
if(k==2)
printf("\n%d is a prime factor",i);
}
i++;
}
getch();
}
13. MULTIPLICATION TABLE
void main()
{
int r,i,j,k;
clrscr();
printf("\nEnter the number range:-");
scanf("%d",&r);
for(i=1;i<=r;i++)
{
for(j=1;j<=10;j++)
printf(" %d*%d=%d",i,j,i*j);
printf("\n");
}
getch();
}
14. FACTORIAL OF A NUMBER
void main()
{
int i=1,f=1,num;
clrscr();
printf("\nEnter a number:");
scanf("%d",&num);
while(i<=num)
{
f=f*i;
i++;
}
printf("\nFactorial of %d is:%d",num,f);
getch();
}
15. FIBONACCI SERIES
void main()
{
int i=0,j=1,k=2,r,f;
clrscr();
printf("Enter the number range:");
scanf("%d",&r);
printf("\nFIBONACCI SERIES: ");
printf("%d %d",i,j);
while(k<r)
{
f=i+j;
i=j;
j=f;
printf(" %d",j);
k++;
}
getch();
}

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