Program to input number from user ( negative or positive ) calculate addition of only negative number

Using while loop ::

#include <stdio.h>

void main ()
{
int a ;
int sum = 0 ;
clrscr () ;
while ( a ! = 0 )
{
printf ("\n Enter a number:") ;
scanf ("%d", &a) ;
sum = sum + a ;
a-- ;
}
printf ("\n %d", sum) ;
getch () ;
}

Using for loop ::

#include <stdio.h>

void main ()

{

int a ;

int sum = 0 ;

clrscr () ;

for ( ; a != 0 : a-- )

{

printf ("\n Enter a number:") ;

scanf ("%d", &a) ;

sum = sum + a ;

}

printf ("\n %d", sum) ;
getch () ;
}

Output ::

Enter number :   5 , 6 , -7 ,-8 

sum =  -7 + -8 = -15

Enter a number : 5 , 6

output = nothing