Thread: Sum of octals found in input

I really want to understand character I/O in C but I feel like my understanding is faulty about certain concepts. I wanna write a program that gives me the sum of all base-8 numbers found in input, but the sum is never incremented.

Code:

/* Write a function that reads data from standard input until EOF is found and returns the sum of the base-8 numbers found into the input.
 We consider a number in base-8 a sequence that starts with 0 and is followed by digits from range [0-7].
 The numbers must be separated from other words by at least one whitespace.
  All the numbers and the final sum are guaranteed to fit in "unsigned" data type. */


  #include <stdio.h>


  int main(){
      int current, last;
      unsigned sum=0;
      int n = 0;
    printf("Enter text:\n");
     current = getchar();
     while(current != '\n'){
            putchar(current);
            last = current;
            current = getchar();
        if(last == '0' && isdigit(current)){
            last = current;
            current = getchar();
            while(isdigit(current)){
                n = current- '0';
                sum = sum+n;
            }
        }
     }


     printf("\nThe sum is %d", sum);
     return 0;
  }

Input: John has 033 apples and 02 strawberries
Output:
John has 033 apples and 02 strawberries
The sum is 0
Please bear in mind that, although I am familiar with strings, I shouldn't really use them for this solution (not that I'd know how to anyway). 'current' and 'last' are meant to define the current char and the last char from the input. I don't really understand how can I 'construct' my number from the characters, since I don't have to add them digit by digit but as whole numbers. Could you help me?

> n = 'current'- 0;
Why the single quotes?

Why doesn't your compiler complain?
C++ Shell

while(isdigit(current))
Isn't going to exit, because current never changes.

Code:

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

#define  true 1
#define false 0

int i, j, x, y, c, r, isOctal = false ;
char currentChar, octalDelim[1024] ;
float totalValue = 0.0 ;

void retrieveOctals( char *fromData ) { i = 0 ;
   while ( i < strlen(fromData) ) {
    currentChar = fromData[i] ; 
    switch (currentChar) {
      case ' ':
        isOctal = false ; 
        if (octalDelim[c-1] != ',')
          octalDelim[c++] = ',' ;
        if ( fromData[i+1] == '0' )
          isOctal = true ;
      break;
      default:
        if ( isOctal ) octalDelim[c++] = fromData[i];
      break;
    }; i++;
  }
}

int main( int args, char * argv[] ) {
   
  char *testInput = "only 064536 octals 345 no 05673 numbers";
  retrieveOctals( testInput );
  printf( "\n%s\n", octalDelim );

  return 0;
}