Mega16 keypad and digital display program

#include  
#define No_key 255 
#define K1_11 
#define K1_22 
#define K1_33 
#define K1_4    4 
#define K2_15 
#define K2_26 
#define K2_37 
#define K2_4    8 
#define K3_19
#define K3_20
#define K3_310
#define K3_4 11
#define K4_112
#define K4_213
#define K4_314
#define K4_4 15
#define Key_mask0b00001111   
#define data PORTB.0 
#define clk PORTB.1  
flash unsigned char led[16]={0x28,0xeb,0x19,0x89,0xca,0x8c,0x0c,0xe9,0x08,0x88, 
                             0xdf,0x4a,0x1c,0x3e,0x7e,0x2a}; 
unsigned charkey_stime_counter; 
unsigned char   key_temp; 
bitkey_stime_ok;  
//D0 is connected to the keyboard, the lower 4 bits are column line input, and the upper 4 bits are row line output
unsigned char read_keyboard() 
{ 
 static unsigned char key_state = 0, key_value, key_line; 
 unsigned char key_return = No_key,i; 
 switch (key_state) 
 { 
  case 0: 
  key_line = 0b00010000; 
  for (i=1; i<=4; i++) // Scan the keyboard
  { 
         PORTA = ~key_line; // Output line level
 PORTA = ~key_line; // Must be sent twice!!!
 key_value = Key_mask & PINA; // Read column level
 if (key_value == Key_mask) 
 key_line <<= 1; // No key pressed, continue scanning
 else 
 {
  key_state++; // Stop scanning when a key is pressed
  break; // Switch to debounce confirmation state
 } 
} 
break; 
  case 1: 
        if (key_value == (Key_mask & PINA)) // Read the column level again,
{
 switch (key_line | key_value) // Same as state 0, confirm key
 {//Keyboard encoding, return encoding value  
  case 0b00011110: 
       key_return = K1_1; 
       break; 
  case 0b00011101: 
       key_return = K1_2; 
       break;
          case 0b00011011: 
       key_return = K1_3; 
       break;
  case 0b00010111: 
       key_return = K1_4; 
       break;      
  case 0b00101110: 
       key_return = K2_1; 
       break;
   case 0b00101101: 
       key_return = K2_2; 
       break;
  case 0b00101011: 
       key_return = K2_3; 
       break;
  case 0b00100111: 
       key_return = K2_4; 
       break;
   case 0b01001110: 
       key_return = K3_1; 
       break;
   case 0b01001101: 
       key_return = K3_2; 
       break;
  case 0b01001011: 
       key_return = K3_3; 
       break;  
  case 0b01000111: 
       key_return = K3_4; 
       break;
   case 0b10001110: 
       key_return = K4_1; 
       break;
   case 0b10001101: 
       key_return = K4_2; 
       break;
  case 0b10001011: 
       key_return = K4_3; 
       break;  
  case 0b10000111: 
       key_return = K4_4; 
       break;
 }
key_state++; // Enter the state of waiting for key release
       } 
       else 
 {
  key_state--; 
  delay_ms(5); 
 }// The two column levels are different and return to status 0 (debounce processing)
 break; 
  Case 2: Waiting for the button to be released
      PORTA = 0b00001111; // All lines output low level
      PORTA = 0b00001111; // repeat once
      if ( (Key_mask & PINA) == Key_mask) 
      key_state=0; // All column lines are high level and return to state 0
      break; 
 }
 return key_return; 
}
//Send data to the digital tube
void sendbyte(unsigned char byte) 
{     
 unsigned char num,c;  
 num=led[byte]; 
 for(c=0;c<8;c++) 
 {
  clk=0; 
  data=num&0x01; 
  clk=1; 
  num>>=1; 
 }
}
void display(void) 
{
 if (key_stime_ok) 
  {
   key_stime_ok = 0; // 10ms to
   key_temp = read_keyboard(); // Call the keyboard interface function to read the keyboard
   if (key_temp != No_key) 
   {// A key is pressed
    sendbyte(key_temp); 
    delay_ms(10); 
   } 
  } 
}
void main(void) 
{
 DDRB = 0xFF; 
 //PORTC = 0xFF; //Keyboard interface initialization
 DDRA = 0xF0; // PD2, PD1, PD0 column lines, input mode, pull-up valid
 //T/C0 initialization  
 TCCR0=0x0B; // Internal clock, 64 division (4M/64=62.5KHz), CTC mode
 TCNT0=0x00; 
 OCR0=0x7C;// OCR0 = 0x7C(124),(124+1)/62.5=2ms 
 TIMSK=0x02; // Enable T/C0 compare match interrupt
 #asm("sei")// Open global interrupt
 while (1) 
 { 
  display(); 
 } 
}      
// Timer 0 compare match interrupt service, 2ms timing
interrupt [TIM0_COMP] void timer0_comp_isr(void) 
{ 
 //display();// Call LED scan display
 if (++key_stime_counter >=5) 
 {
  key_stime_counter = 0; 
  key_stime_ok = 1; // 10ms to
 }
}