#include<stdio.h>
void plus(float);
void minus(float);


int main(void)
{
  float p=0,a;
  int e;
  char c;
  
  printf("please input minuend p:\40");
  scanf("\40%f", &p);
  printf("please input'+'||'-':  ");
  scanf("%c", &c);
  e = c;
  
  
  if(43==e)
   plus(p);
  if(45==e)
   minus(p);
  return 0;
}

void plus(float p )
{
  float e,a;
  printf("please input minuend e:\40");
  scanf("\40%f", &e);
  printf("\40\40\40\40%-.1f\n", p);
  printf("\40\40+\40%-.1f\n", e);
  printf(".........\n");
  printf("\40\40\40%-.1f\n", a=(p+e));
  printf("please go on\n");
}
void minus(float p)
{
  float e,a;
  printf("please input minuend e:\40");
  scanf("\40%f", &e);
  printf("\40\40\40\40%-.1f\n", p);
  printf("\40\40-\40%-.1f\n", e);
  printf(".........\n");
  printf("\40\40\40%-.1f\n", a=(p-e));
  printf("please go on\n");
  
}

出了什么问题?

//scanf("%c", &c);
scanf("\40%c", &c);