Embedded C tricky Question

 

Embedded C Programming

1. Write an Embedded C program to multiply any number by 9 in the fastest manner.

This can be achieved by involving bit manipulation techniques - Shift left operator as shown below:

#include<stdio.h>
void main(){
    int num;
    printf(“Enter number: ”);
    scanf(“%d”,&num);
    printf(“%d”, (num<<3)+num);
}

2. How will you swap two variables? Write different approaches for the same.

• Using Extra Memory Space:

int num1=20, num2=30, temp;
temp = num1;
num1 = num2;
num2 = temp;

• Using Arithmetic Operators:

int num1=20, num2=30;
num1=num1 + num2;
num2=num1 - num2;
num1=num1 - num2;

• Using Bit-Wise Operators:

int num1=20, num2=30;
num1=num1 ^ num2;
num2=num2 ^ num1;
num1=num1 ^ num2;

• Using One-liner Bit-wise Operators:

int num1=20, num2=30;
num1^=num2^=num1^=num2;

The order of evaluation here is right to left.

• Using One-liner Arithmetic Operators:

int num1=20, num2=30;
num1 = (num1+num2)-(num2=num1);

Here the order of evaluation is from left to right.

3. Write a program to check if a number is a power of 2 or not.

We can do this by using bitwise operators.

void main (){
    int num;
    printf ("Enter any no:");
    scanf ("%d", &num);
    if (num & & ((num & num-1) == 0))
        printf ("Number is a power of 2");
    else
        printf ("Number is not a power of 2");
}

4. Write a program to print numbers from 1 to 100 without making use of conditional operators?

void main (){
   int i=0;
   while (100 – i++)
   printf ("%d", i);
}

5. Write a MIN macro program that takes two arguments and returns the smallest of both arguments.

#define MIN(NUM1,NUM2) ( (NUM1) <= (NUM2) ? (NUM1) : (NUM2) )