硬件部分比较简单，当键盘按键按下时它的那一行、那一列的端口为低电平。因此，只要扫描行、列端口是否都为低电平就可以确定是哪个键被按下。
二、主程序流程图
程序的主要思想是：将按键抽象为字符，然后就是对字符的处理。将操作数分别转化为字符串存储，操作符存储为字符形式。然后调用compute()函数进行计算并返回结果。具体程序及看注释还有流程图。
三、程序源代码#include <reg51.h>#include <intrins.h> #include <ctype.h> #include <stdlib.h>
#define uchar unsigned char #define uint unsigned int
uchar operand1[9], operand2[9]; uchar operator;
void delay(uint); uchar keyscan(); void disp(void); void buf(uint value); uint compute(uint va1,uint va2,uchar optor);
uchar code table[] = {0xc0,0xf9,0xa4,0xb0,0x99, 0x92,0x82,0xf8,0x80,0x90,0xff};
uchar dbuf[8] = {10,10,10,10,10,10,10,10};
void delay(uint z) { uint x,y; for(x=z;x>0;x--) for(y=110;y>0;y--); }
uchar keyscan() { uchar skey;
P1 = 0xfe; while((P1 & 0xf0) != 0xf0) { delay(3);
while((P1 & 0xf0) != 0xf0) { switch(P1) { case 0xee: skey = '7'; break; case 0xde: skey = '8'; break; case 0xbe: skey = '9'; break; case 0x7e: skey = '/'; break;
default: skey = '#'; }
while((P1 & 0xf0) != 0xf0) ; } }
P1 = 0xfd; while((P1 & 0xf0) != 0xf0) { delay(3);
while((P1 & 0xf0) != 0xf0) { switch(P1) { case 0xed: skey = '4'; break; case 0xdd: skey = '5'; break; case 0xbd: skey = '6'; break; case 0x7d: skey = '*'; break;
default: skey = '#'; }
while((P1 & 0xf0) != 0xf0) ; } }
P1 = 0xfb; while((P1 & 0xf0) != 0xf0) { delay(3);
while((P1 & 0xf0) != 0xf0) { switch(P1) { case 0xeb: skey = '1'; break; case 0xdb: skey = '2'; break; case 0xbb: skey = '3'; break; case 0x7b: skey = '-'; break;
default: skey = '#'; }
while((P1 & 0xf0) != 0xf0) ; } }
P1 = 0xf7; while((P1 & 0xf0) != 0xf0) { delay(3);
while((P1 & 0xf0) != 0xf0) { switch(P1) { case 0xe7: skey = '$'; break; case 0xd7: skey = '0'; break; case 0xb7: skey = '='; break; case 0x77: skey = '+'; break;
default: skey = '#'; }
while((P1 & 0xf0) != 0xf0) ; } }
return skey; }
void main() { uint value1, value2, value; uchar ckey, cut1 = 0, cut2 = 0; uchar operator; uchar i, bool = 0;
init:
buf(0); disp(); value = 0; cut1 = cut2 = 0; bool = 0; for(i = 0;i < 9;i++) { operand1 = '\0'; operand2 = '\0'; }
while(1) { ckey = keyscan(); if(ckey != '#') { if(isdigit(ckey)) { switch(bool) { case 0: operand1[cut1] = ckey; operand1[cut1+1] = '\0'; value1 = atoi(operand1); cut1++; buf(value1); disp(); break; case 1: operand2[cut2] = ckey; operand2[cut2+1] = '\0'; value2 = atoi(operand2); cut2++; buf(value2); disp(); break;
default: break; } } else if(ckey=='+'||ckey=='-'||ckey=='*'||ckey=='/') { bool = 1; operator = ckey; buf(0); dbuf[7] = 10; disp(); } else if(ckey == '=') { value = compute(value1,value2,operator); buf(value); disp(); while(1) { ckey = keyscan(); if(ckey == '$') goto init; else { buf(value); disp(); } } } else if(ckey == '$') { goto init;} } disp(); }
}
uint compute(uint va1,uint va2,uchar optor) { uint value;
switch(optor) { case '+' : value = va1+va2; break; case '-' : value = va1-va2; break; case '*' : value = va1*va2; break; case '/' : value = va1/va2; break;
default : break; } return value; }
void buf(uint val) { uchar i; if(val == 0) { dbuf[7] = 0; i = 6; }
else for(i = 7; val > 0; i--) { dbuf = val % 10; val /= 10; }
for( ; i > 0; i--) dbuf = 10; }
void disp(void) { uchar bsel, n;
bsel=0x01; for(n=0;n<8;n++) { P2=bsel; P0=table[dbuf[n]]; bsel=_crol_(bsel,1); delay(3); P0=0xff; } } | 
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