C programs – (Miscellaneous)

1. Write a logic in C language to find whether the given system is Little endian or Big endian

#include <stdio.h>
int main()
{
        int a = 0x1;
        char *ptr = (char *)&a;

        if (*ptr == 1)
                printf("the system is little endian\n");

        else

                printf("The system is big endian\n");

}

Explaination

As discussed in the Endianness chapter, if the system is little endian, the value 1 is stored at the lower memory address of a variable. In a big endian system, the value 1 is stored at the higher memory address. When a variable’s address is assigned to a pointer, the pointer holds the lower memory address of the variable. By dereferencing the pointer as a character pointer, we can access the value stored at the lower memory address of the variable.

2. Convert the data in a given variable to big endian.

#include <stdio.h>

int to_be32(int num)
{
        int tmp = 0;

        tmp = (num << 24) & 0xff000000;
        tmp |= (num << 8) & 0x00ff0000;
        tmp |= (num >> 8) & 0x0000ff00;
        tmp |= (num >> 24) & 0x000000ff;
       
        return tmp;
}

int main()
{
        int a = 0x1, num;
        char *ptr = (char *)&a;

        printf("Enter value to convert into big endian:");
        scanf("%i", &num);

        if (*ptr == 1) {
                num = to_be32(num);
                printf("The value in big endian is: 0x%x\n", num);
        } else
                printf("The system is big endian no need for conversion\n");
}

Explaination

Before converting into big endian, we have to find what is the endianess of the system. For this we used program 1 to find out. If the system is little endian then conversion is needed. The function to_be32() converts given 32 bit value into big endian format and returns the converted value.

5. Convert binary input to its respective decimal value:

Sample input: 101
output: 5

#include <stdio.h>
#include <string.h>
/*
 * powof - function to calculate x power y
 */
int powof(int x, int y)
{
        int pow = 1;
        if (y == 0)
                return 1;
        while (--y)
                pow *= x;
       
        return pow;
}

int main()
{
        char str[32];
        int i;
        int val = 0;

        printf("Enter a binary value:");
        scanf("%s", str);

        for (i = strlen(str) - 1; i >= 0; i--) {
                if ((str[i] != '1') && (str[i] != '0')) {
                        printf("invalid binary input\n");
                        return 0;
                }
                if (str[i] == '1')
                        val += powof(2, strlen(str) - i);
        }

        printf("val = %d\n", val);
}

input:

1011001

output:

89

6. Convert a given Decimal input to its respective Binary representation:

Sample input: 8
output: 1000

#include <stdio.h>

int main()
{
        int i;
        int val = 0;

        printf("Enter a decimal value:");
        scanf("%d", &val);

        for (i = 31; i >= 0; i--)
                 (val >> i & 0x1) ? printf("1") : printf("0");

}

input:

42

output:

00000000000000000000000000101010

7. Swap value in two variables without using temporary variable

#include <stdio.h>

int main()
{
        int x = 10, y = 40;

        printf("x=%d, y=%d\n", x, y);

        x = x + y;
        y = x - y;
        x = x - y;

        printf("x=%d, y=%d\n", x, y);
}

output:

x=10, y=40
x=40, y=10

8. Check the given number is palindrome or not.

A number is said to be a palindrome if, when the number is reversed, it remains the same as the original number.

sample input1 : 34543
output: The given number is palindrome

sample input2 : 6777
output: The given number is not a palindrome

#include <stdio.h>

int main()
{
        int num, tmp;
        int val = 0;

        printf("Enter a number:");
        scanf("%d", &num);

        tmp = num;
        while(tmp) {
                val = val * 10 + tmp % 10;
                tmp /= 10;
        }
        printf("val=%d\n", val);
        if (val == num)
                printf("the given number is palindrome\n");
        else   
                printf("the given number is not a palindrome\n");
}

input:

121

output:

The given number is palindrome.

C programs – Part 2 (bitwise operations)

C programs – Part 3 (arrays)

C programs – Part 4 (strings)