Question

1) Write a C program that reads a hexadecimal value from the keyboard and then stores the value into an unsigned char variable. Read two int values p and n from the keyboard, where the values are less than 8. Implement the following commands: S – sets the n bits starting at position p to 11..1 R – resets the n bits starting at position p to 00…0 F – flips the n bits starting at position p to their inverse bit D – displays the value of the variable I – reads a new hexadecimal value from the keyboard

2) Repeat exercise 1 using a variable of type unsigned int. Discuss the differences between the two programs.

Answer 1

solution:

Following are the screenshots of code and output:

Part 1)

Part 2)

Or operation is used for setting ; And for resetting ; Xor for flipping.

The only difference between two programs is that the variable in second program(unsigned char) can store 32 bits while the variable in first program(unsigned int) can store only 8 bits.Thus in first program the maximum value of n & p can be 8 ,while in second program it can be upto 32.

C program for part 1

#include<stdio.h>

int main(){

//using unsigned char

unsigned char var;

int p,n;

//inputting values

printf("a = ");

scanf("%x",&var);

printf("p = ");

scanf("%d",&p);

printf("n = ");

scanf("%d",&n);

while(1){

char command;

scanf("%c",&command);

//implementing commands

if(command=='S'){

var=var | (((1<<n)-1)<<(p-1));

}

else if(command=='R'){

var=var & ~(((1<<n)-1)<<(p-1));

}

else if(command=='F'){

var=var ^ (((1<<n)-1)<<(p-1));

}

else if(command=='D'){

//displaying in hexadecimal

printf("a = %02x H : ",var);

int i;

//displaying in binary

for(i=7;i>=4;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=3;i>=0;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" B\n");

}

else if(command=='I'){

printf("a = ");

scanf("%x",&var);

}

}

}

C program for part 2

#include<stdio.h>

int main(){

//using unsigned int

unsigned int var;

int p,n;

//inputting values

printf("a = ");

scanf("%x",&var);

printf("p = ");

scanf("%d",&p);

printf("n = ");

scanf("%d",&n);

while(1){

char command;

scanf("%c",&command);

//implementing commands

if(command=='S'){

var=var | (((1<<n)-1)<<(p-1));

}

else if(command=='R'){

var=var & ~(((1<<n)-1)<<(p-1));

}

else if(command=='F'){

var=var ^ (((1<<n)-1)<<(p-1));

}

else if(command=='D'){

//displaying in hexadecimal

printf("a = %08x H : ",var);

int i;

//displaying in binary

for(i=31;i>=28;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=27;i>=24;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=23;i>=20;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=19;i>=16;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=15;i>=12;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=11;i>=8;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=7;i>=4;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" ");

for(i=3;i>=0;i--)

printf("%d",((1<<i)&(var))>>i);

printf(" B\n");

}

else if(command=='I'){

printf("a = ");

scanf("%x",&var);

}

}

}

please give me thumb up