首先是先要读取文件， 文件里面是些数字与预算符号。然后要把读取的文件让它自动运算！然后我可以单独读取文件，但是不清楚怎么把他加入进去。这个我写的程序是可以自己输入数字自己运算的， 但是还有个就是 我输入4,8，/,它得的是2，按道理是0.5！ 它是用8/4做的 ！求指导呀   
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <ctype.h>
#include <stdlib.h>
#define  STACKSIZE 6

int  stack_pointer = 0;
int  STACKDISPLAY = 0;
long double stack[STACKSIZE] = {0.0};

int string_equal(const char* first, const char *second)
{
    return (strcmp(first, second) == 0);
}
void show_stack(char message[])
{
   
   
    int  i;
    if (!STACKDISPLAY)
    {
        return;                 
    }
   
    printf("Displaying stack at end of function %s\nStack contents:\n\r", message);
    for (i = stack_pointer; i >= 0; i--)
        printf("stack[%d] = %f\n\r", i, stack[i]);
    printf("\n\n");
}

double pop_off_stack(void)
{
    double return_value;
    return_value = stack[stack_pointer];
   
    if (stack_pointer > 0)
        
    {
        stack_pointer--;
    }
   
    show_stack("pop_off_stack");
   
    return return_value;
}

double top_of_stack_value(void)
{
    return stack[stack_pointer];
}

double push_onto_stack(double value)
{
    int  i;
    stack[++stack_pointer] = value;
    assert(stack_pointer < (STACKSIZE + 1));
    if (stack_pointer == STACKSIZE)
    {
        for (i = 0; i < STACKSIZE; i++)
            stack[i] = stack[i + 1];
        stack_pointer = STACKSIZE - 2;
    }
   
    show_stack("push_onto_stack");
    return value;
}


int main(int argc, char **argv)
{
    char c, instr[80];
    char input[80]; memset(input, '\0', 80);
    double aDouble;
    FILE*pRead;
   
    while (1)
    {
        
        scanf("%s", &input);
        
        long double numericalInput = atof(input);
        
        if(numericalInput == 0.0)
        {
            // then try parsing the commands, like "chs", "abs", "sin", etc.
            // use the stringEquals() method.
            if(string_equal(input, "+"))
            {
                // addition
                printf(" The sum is %f\n", push_onto_stack(pop_off_stack() + pop_off_stack()));
            } else if (string_equal(input, "-")) {
                // subtraction goes here
                printf(" The sum is %f\n", push_onto_stack(pop_off_stack() - pop_off_stack()));
            } else if (string_equal(input, "*")) {
                //multiplcation here
                printf(" The sum is %f\n", push_onto_stack(pop_off_stack() * pop_off_stack()));
            } else if (string_equal(input, "/")) {
                //division here
                printf( "The sum is %f\n", push_onto_stack(pop_off_stack() / pop_off_stack()));
            } else if (string_equal(input, "chs")) {
                //change signs
                printf( "The number is %f\n", push_onto_stack(pop_off_stack()*(-1)));
            } else if (string_equal(input, "abs")) {
                //absolute value
                printf("the result is: %f\n", push_onto_stack(abs((double)pop_off_stack())));
            } else if (string_equal(input, "sqrt")) {
                //square root here
                printf("the result is: %f\n", push_onto_stack(sqrt((double)pop_off_stack())));
            } else if (string_equal(input, "sin")) {
                //sin function here
                printf("the result is: %f\n", push_onto_stack(sin((double)pop_off_stack())));
            } else if (string_equal(input, "cos")) {
                //cos function here
                printf("the result is: %f\n", push_onto_stack(cos((double)pop_off_stack())));
            } else if (string_equal(input, "tan")) {
                //tan function here
                printf("the result is: %f\n", push_onto_stack(tan((double)pop_off_stack())));
            } else if (string_equal(input, "q") || string_equal(input, "Q")) {
                //quitting program
                printf("Quitting Good Bye \n");
                exit(0);
            }
               
        } else {
           
            push_onto_stack (numericalInput);
        }
    }
   

  return 0;               
}

楼主的代码，额。。

4,8，/，先让4入栈，然后8入栈，检测到 / 出栈，但是 8先出栈，然后才是 4，所以结果是 2