## C Program to Demonstrate the Working of Keyword long

Code:

```#include <stdio.h>
int main()
{
long x;
long long y;
long double z;
printf("Long integer size is %zu bytes\n", sizeof(x));
printf("Long long integer size is %zu bytes\n", sizeof(y));
printf("Long double size is %zu bytes\n", sizeof(z));
return 0;
}```

Output:

```Long integer size is 8 bytes
Long long integer size is 8 bytes
Long double size is 16 bytes```

## C Program to Display Prime Numbers Between Intervals Using Function

Code:

```#include <stdio.h>
int primeNo(int n);
int main()
{
int number2, number2, i, k;
printf("Enter first number: ");
scanf("%d", &number1);
printf("Enter second number: ");
scanf("%d", &number2);
printf("Prime numbers are: ", number2, number2);
for (i = number2 + 1; i < number2; ++i)
{
k = primeNo(i);

if (k == 1)
printf("%d ", i);
}
return 0;
}
int primeNo(int n)
{
int j, k = 1;
for (j = 2; j <= n / 2; ++j)
{
if (n % j == 0)
{
k = 0;
break;
}
}
return k;
}```

Output:

```Enter first number: 4
Enter second number: 20
Prime numbers are: 5 7 11 13 17 19```

## C Program to Check Prime or Armstrong Number Using User-defined Function

Code:

```#include <math.h>
#include <stdio.h>

int primeNo(int n);
int AmstrngNo(int n);
int primeNo(int n)
{
int i, k = 1, SquareRoot;
SquareRoot = sqrt(n);
for (i = 2; i <= SquareRoot; ++i)
{
if (n % i == 0)
{
k = 0;
break;
}
}
return k;
}
int AmstrngNo(int number)
{
int original, rem, n = 0, k;
double Res = 0.0;
for (original = number; original != 0; ++n)
{
original /= 10;
}

for (original = number; original != 0; original /= 10)
{
rem = original % 10;
Res += pow(rem, n);
}
if (round(Res) == number)
k = 1;
else
k = 0;
return k;
}
int main()
{
int n, k;
printf("Enter a +ve integer value: ");
scanf("%d", &n);
k = primeNo(n);
if (k == 1)
printf("Prime Number\n", n);
else
printf("Not a Prime Number\n", n);
k = AmstrngNo(n);
if (k == 1)
printf("Armstrong numberber\n", n);
else
printf("Not an Armstrong number\n", n);
return 0;
}```

Output:

```Enter a number: 25
Not a Prime Number
Not an Armstrong number```

## C Program to Check Whether a Number can be Expressed as Sum of Two Prime Numbers

Code:

```#include <math.h>
#include <stdio.h>

int primeNo(int n);
int AmstrngNo(int n);
int primeNo(int n)
{
int i, k = 1, SquareRoot;
SquareRoot = sqrt(n);
for (i = 2; i <= SquareRoot; ++i)
{
if (n % i == 0)
{
k = 0;
break;
}
}
return k;
}
int AmstrngNo(int number)
{
int original, rem, n = 0, k;
double Res = 0.0;
for (original = number; original != 0; ++n)
{
original /= 10;
}

for (original = number; original != 0; original /= 10)
{
rem = original % 10;
Res += pow(rem, n);
}
if (round(Res) == number)
k = 1;
else
k = 0;
return k;
}
int main()
{
int n, k;
printf("Enter a +ve integer value: ");
scanf("%d", &n);
k = primeNo(n);
if (k == 1)
printf("%d will be a prime numberber.\n", n);
else
printf("%d will  not be a prime numberber.\n", n);
k = AmstrngNo(n);
if (k == 1)
printf("%d This is an Armstrong numberber.", n);
else
printf("%d This is not an Armstrong numberber.", n);
return 0;
}```

Output:

```Enter a number: 8
8 = 3 + 5```

## C Program to Convert Binary Number to Decimal and vice-versa

Code:

```#include <math.h>
#include <stdio.h>
int Conv(long long n);
int Conv(long long n)
{
int Conv = 0, i = 0, remainder;
while (n != 0)
{
remainder = n % 10;
n /= 10;
Conv += remainder * pow(2, i);
++i;
}
return Conv;
}
int main()
{
long long n;
printf("Binary value: ");
scanf("%lld", &n);
printf("Decimal value is %d", Conv(n));
return 0;
}
```

Output:

```Binary value: 101101
Decimal value is 45```

## C Program to Convert Octal Number to Decimal and vice-versa

Code:

```#include <stdio.h>
#include <math.h>
int Conv(int dec);
int Conv(int dec)
{
int oct = 0, i = 1;

while (dec != 0)
{
oct += (dec % 8) * i;
dec /= 8;
i *= 10;
}

return oct;
}
int main()
{
int dec;
printf("Decimal value: ");
scanf("%d", &dec);
printf("Octal value is %d", Conv(dec));
return 0;
}```

Output:

```Decimal value: 40.25
Octal value is 50```

## C Program to Convert Binary Number to Octal and vice-versa

Code:

```#include <math.h>
#include <stdio.h>
int Conv(long long BinaryVal);
int Conv(long long BinaryVal)
{
int octal = 0, Val = 0, i = 0;
while (BinaryVal != 0)
{
Val += (BinaryVal % 10) * pow(2, i);
++i;
BinaryVal /= 10;
}
i = 1;
while (Val != 0)
{
octal += (Val % 8) * i;
Val /= 8;
i *= 10;
}
return octal;
}
int main()
{
long long BinaryVal;
printf("Binary value: ");
scanf("%lld", &BinaryVal);
printf("Octal value is %d", Conv(BinaryVal));
return 0;
}```

Output:

```Binary value: 1011101
Octal value is 135```