Balancing of Symbols

#include<stdio.h>
#include<malloc.h>
struct stack
{
	char *array;
	int capacity;
	int top;
};

int isStackEmpty(struct stack S)
{
	if(S.top==0)
	return 1;
	else
	return 0;
}

void stackPush(struct stack *S,char element)
{
if(isStackFull(*S))
   return ;
   S->array[S->top]=element;
   S->top++;	
}

int isStackFull(struct stack S)
{
	if(S.top==S.capacity)
	return 1;
	else
	return 0;
}

char stackPop(struct stack *S)
{
	if(isStackEmpty(*S))
	return '\0';
	S->top--;
	return S->array[S->top];
}

int checkBalance(char array[])
{
	int i;
	struct stack S;
	S.top=0;
	S.capacity=10;
	S.array=(char*)malloc(S.capacity*sizeof(char));
	for(i=0;array[i]!='\0';i++)
	{
		  if((array[i]=='{')||(array[i]=='[')||(array[i]=='('))
		  {
		    stackPush(&S,array[i]);
		}
	    	else if(array[i]=='}')
		    {
		       if(stackPop(&S)!='{')
		     return 0;	
			}
		  else if(array[i]==']')
		  {
		  	if(stackPop(&S)!='[')
		  	 return 0;
		  }
		                            
		  else if(array[i]==')' )
		  {
		  	if(stackPop(&S)!='(')
		  	 return 0;
		  }
		            
	}
	    if(isStackEmpty(S))
	           return 1;
	    else 
	           return 0;
}

void main()
{
	int result=0;
	char expr[20];
    struct stack S;
	S.top=0;
	S.capacity=10;
	S.array=(char*)malloc(S.capacity*sizeof(char));
	printf("Enter the expression:");
	scanf("%s",expr);
	result=checkBalance(expr);
	if(result)
	{
	printf("\n Expression is  balanced in terms of Symbols");
    }
	else
	{
	printf("\n Expression is not balanced in terms of Symbols");
    }
}