#include<stdio.h>
#define MAX 1000

int main(){
   
    char binaryNumber[MAX],octalNumber[MAX];
    long int i=0,j=0;

    printf("Enter any number any binary number: ");
    scanf("%s",binaryNumber);

    while(binaryNumber[i]){
      binaryNumber[i] = binaryNumber[i] -48;
      ++i;
    }

    --i;
    while(i-2>=0){
    octalNumber[j++] = binaryNumber[i-2] *4 +  binaryNumber[i-1] *2 + binaryNumber[i] ;
    i=i-3;
    }

    if(i ==1)
      octalNumber[j] = binaryNumber[i-1] *2 + binaryNumber[i] ;
    else if(i==0)
      octalNumber[j] =  binaryNumber[i] ;
    else
      --j;

    printf("Equivalent octal value: ");
    while(j>=0){
      printf("%d",octalNumber[j--]);
    }

    return 0;
}
Sample output:
Enter any number any binary number: 1111111111111111111
1111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111
1111111111111111111111111111111111111111111111111111111
11111111
Equivalent octal value: 3777777777777777777777777777777
7777777777777777777777777777777777777777777777777777

#include<stdio.h>

int main(){
   
    long int binaryNumber,decimalNumber=0,j=1,remainder;

    printf("Enter any number any binary number: ");
    scanf("%ld",&binaryNumber);

    while(binaryNumber!=0){
         remainder=binaryNumber%10;
        decimalNumber=decimalNumber+remainder*j;
        j=j*2;
        binaryNumber=binaryNumber/10;
    }

    printf("Equivalent decimal value: %ld",decimalNumber);

    return 0;
}
Sample output:
Enter any number any binary number: 1101
Equivalent decimal value: 13

#include<stdio.h>
int main(){
   
    long int binaryNumber,hexadecimalNumber=0,j=1,remainder;
   
    printf("Enter any number any binary number: ");
    scanf("%ld",&binaryNumber);
   
    while(binaryNumber!=0){
    remainder=binaryNumber%10;
    hexadecimalNumber=hexadecimalNumber+remainder*j;
        j=j*2;
        binaryNumber=binaryNumber/10;
      }
   
    printf("Equivalent hexadecimal value: %lX",hexadecimalNumber);

    return 0;
}
Sample output:
Enter any number any binary number: 1101
Equivalent hexadecimal value: D

#include<stdio.h>
#define MAX 1000

int main(){

   char binaryNumber[MAX],hexaDecimal[MAX];
   int temp;
   long int i=0,j=0;
  
   printf("Enter any number any binary number: ");
   scanf("%s",binaryNumber);

   while(binaryNumber[i]){
      binaryNumber[i] = binaryNumber[i] -48;
      ++i;
   }

   --i;
   while(i-2>=0){
       temp =  binaryNumber[i-3] *8 + binaryNumber[i-2] *4 +  binaryNumber[i-1] *2 + binaryNumber[i] ;
       if(temp > 9)
            hexaDecimal[j++] = temp + 55;
       else
            hexaDecimal[j++] = temp + 48;
       i=i-4;
   }

   if(i ==1)
      hexaDecimal[j] = binaryNumber[i-1] *2 + binaryNumber[i] + 48 ;
   else if(i==0)
      hexaDecimal[j] =  binaryNumber[i] + 48 ;
    else
      --j;

   printf("Equivalent hexadecimal value: ");
   while(j>=0){
      printf("%c",hexaDecimal[j--]);
   }

   return 0;
}
Sample output:
Enter any number any binary number: 1010011011100011110
001001111011110001000100011101110111011110
Equivalent hexadecimal value: 14DC789EF111DDDE

#include<stdio.h>

int main(){

    long int binary1,binary2;
    int i=0,remainder = 0,sum[20];

    printf("Enter any first binary number: ");
    scanf("%ld",&binary1);
    printf("Enter any second binary number: ");
    scanf("%ld",&binary2);

    while(binary1!=0||binary2!=0){
         sum[i++] =  (binary1 %10 + binary2 %10 + remainder ) % 2;
         remainder = (binary1 %10 + binary2 %10 + remainder ) / 2;
         binary1 = binary1/10;
         binary2 = binary2/10;
    }

    if(remainder!=0)
         sum[i++] = remainder;

    --i;
    printf("Sum of two binary numbers: ");
    while(i>=0)
         printf("%d",sum[i--]);

   return 0;
}
Sample output:
Enter any first binary number: 1100011
Enter any second binary number: 1101
Sum of two binary numbers: 1110000