Question

Since communications channels are often noisy, numerous ways have been devised to ensure reliable data transmission. One successful method uses a checksum. A checksum for a message can be computed by summing the integer codes of the characters in the message and finding the remainder of this sum divided by 64. The integer code for a space character is added to this result to obtain the checksum. Since this value is within the range of the displayable characters, it is displayed as a character as well. Write a program that accepts single-line messages ending with a period and displays the checksum character for each message. Your program should continue displaying checksums until the user enters a line with only a period.

Provided template and program constraints:

Constraints : calc_sum() must have return type of void
             : calc_sum() must have one "output parameter", ie, pass by reference
             : main() must print the results.
Example     : Enter a message:matlab.
Output      : checksum = Q
============================================================================
*/
#include

int main(){
        int sum=0;
        calc_checksum(&sum);
        /* Enter some code here to print result*/
        return 0;
}

Example:

Enter a message:matlab.
checksum = Q                  ^-------- note the period (.) at the end to mark the end.

Note: Do not use an array to solve this problem.

This has to be coded in the C programming language and done by modifying the template code provided.

Answer 1

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

void calc_checksum(int *n)
{
char c;

//now convertint to checksum
int sum=0;
int i=0;
printf("Enter message:");
while(true)
{
//printf("i:%d\n",i);
c=getchar();
if(i==1 && c =='.')
{printf("--exiting--");
exit(0);}
else if(c=='.')
break;
sum=sum+c;//adding integer codes
i++;
}sum=sum%64;//finding reminder
sum+=' ';//space is added
*n=sum;
}
int main(){
int sum=0;
while(1)
{sum=0;
calc_checksum(&sum);
/* Enter some code here to print result*/
//printing result
printf("output:%c\n",(char)sum);
}return 0;
}

output:

Enter message:matlab.
output:Q
Enter message:hello.
output:>
Enter message:surya.
output:^
Enter message:.
--exiting--

Process exited normally.
Press any key to continue . . .