#include<reg52.h>
sbit PWM=P1^0;
sbit key1=P3^0;
sbit key2=P3^1;
sbit key3=P3^2;
sbit key4=P3^3;
char temp;
void key();
void delay(int z)
{
int i,j;
for(i=0;i<10;i++)
for(j=z;j>0;j--);
}
void main()
{
int a;
temp=0;
while(1)
{
key();
for(a=0;a<100;a++)
{
key();
if(a<temp)
PWM=1;
else
PWM=0;
delay(1);
}
}
}
void key()
{
if(key1==0)
{
delay(10);
if(key1==0) temp=20;
}
if(key2==0)
{
delay(10);
if(key2==0) temp=40;
}
