#define bvformata(ret, b, fmt, lastarg) { \
bstring bstrtmp_b = (b); \
const char * bstrtmp_fmt = (fmt); \
int bstrtmp_r = BSTR_ERR, bstrtmp_sz = 16; \
	for (;;) { \
		va_list bstrtmp_arglist; \
		va_start (bstrtmp_arglist, lastarg); \
		bstrtmp_r = bvcformata (bstrtmp_b, bstrtmp_sz, bstrtmp_fmt, bstrtmp_arglist); \
		va_end (bstrtmp_arglist); \
		if (bstrtmp_r >= 0) { /* Everything went ok */ \
			bstrtmp_r = BSTR_OK; \
			break; \
		} else if (-bstrtmp_r <= bstrtmp_sz) { /* A real error? */ \
			bstrtmp_r = BSTR_ERR; \
			break; \
		} \
		bstrtmp_sz = -bstrtmp_r; /* Doubled or target size */ \
	} \
	ret = bstrtmp_r; \
}
 

[code=c]	char cedula[11], c; 

	for(i=0;i<9;i++) { 

	char cedula[11], c;

	scanf("%s",&cedula);

			n[i] = atoi(cedula[i]);

	digito10 = suma%10;
	if (suma%10==0)
		digito10=0;

	if (digito10 = n[10])

void validacion() {
	int i, digito10, suma, n[10], pares=0, impares=0, mul;
	char cedula[10], c;
	bool valid=true; /* #include <stdbool.h> */
 
	scanf("%s",cedula);
 
	for(i=0;i<9;i++) {
		c = cedula[i];
		if (isdigit(c))
			n[i] = atoi(cedula);
		else {
			printf("numero de cedula incorrecto\n");
			valid = false;
			break;
		}
	}
 
	if(valid) {
		for(i=0; i<9; i++) {
			if (n[i]%2 == 0) {
				mul = 0;
				mul = n[i]*2;
				if (mul>9)
					mul = mul-9;
				pares = pares+mul;
			} else
				impares = impares+n[i];
		}
 
		suma = impares+pares;
 
		digito10 = suma%10;
		if (digito10 == n[9])
			printf("\n\n\n Numero de cedula valida");
		else {
			printf("\n\n\n Numero de cedula NO valida ");
			printf("\n\n %d = %d\n",digito10,n[9]);
		}
	}
}