Infix to Prefix and Evaluation of Prefix

Programs.c

/* Infix to prefix*/
#include<stdio.h>
#include<ctype.h>
#include<string.h>

# define max 100

void push(char stack[],int * top,char c)
{
	if(*top==max-1)
		printf("Overflow\n");
	else
		stack[++(*top)]=c;
}

char pop(char stack[], int *top)
{
	if(*top==-1)
		printf("Underflow\n");
	else
		return stack[(*top)--];
}

int priority(char c)
{
	if(c==')')
		return 0;
	if(c=='+'||c=='-')
		return 1;
	if(c=='*'||c=='/'||c=='%')
		return 2;
	if(c=='^')
		return 3;
}

display(char stack[],int top)
{
	while(top>-1)
		printf(" %c",stack[top--]);
	printf("\n");
}

void main()
{
	char infix[max],prefix[max],stack[max];
	int top=-1,i=0,j=0;

	printf("Enter infix\t");
	scanf("%s",infix);
	for(i=strlen(infix)-1;i>=0;i--)
	{
		char c=infix[i];
		if(isalnum(c))
			prefix[j++]=c;
		else if(top==-1||c==')')
			push(stack,&top,c);
		else if(c=='(')
			{while(stack[top]!=')')
				prefix[j++]=pop(stack,&top);
			char w=pop(stack,&top);}
		else if(stack[top]=='^' && c=='^')
			{prefix[j++]=pop(stack,&top);
			 push(stack,&top,c);}
		else 
			{while(priority(stack[top])>priority(c))
				prefix[j++]=pop(stack,&top);
				push(stack,&top,c);}
		
	}
	while(top>-1)
		prefix[j++]=pop(stack,&top);

	prefix[j]='\0';
	for(i=strlen(prefix)-1;i>=0;i--)
	printf("%c",prefix[i]);

	
}

/****
****
*****Evaluation of Prefix*
***/

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

#define MAX 50

int stac[MAX];
int top=-1;

push(int ele)
{
    stac[++top]=ele;
}

int pop()
{
    return stac[top--];
}

main()
{
    char postfix[50],c;
    int i,op1,op2;
    printf("Enter expression \n");
    scanf("%s",postfix);
    i=strlen(postfix)-1;
    while(i!=-1)
    {   c=postfix[i--];
        if(isdigit(c))
            push(c-'0');
        else
        {
            op1=pop();
            op2=pop();
            switch(c)
            {
                case '+':push (op1+op2);
                         break;
                case '-':push (op1-op2);
                         break;
                case '*':push (op1*op2);
                         break;
                case '/':push (op1/op2);
                         break;
                case '%':push (op1%op2);
                         break;
                case '$':push (pow(op1,op2));
                         break;

            }
        }
    }
    printf("Ans is %d",stac[top]);

}