Real Basic Question pic microcontrollers

Code C - [expand]
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[CODE]
//Using 20MHz clock
#include <16F877.h>
#use delay(clock=20M)
 
boolean a;
int32 rise, rise2, value;
float freq, period;
 
#int_ccp1
void isr2()
{
  rise=CCP_1; 
} 
 
#int_ccp2
void isr()
{
  rise2 = CCP_2;
  value = rise2 - rise;
  a=1;
} 
void main()
{
   #priority ccp2,ccp1
   setup_ccp1(CCP_CAPTURE_RE); // Configure CCP1 to capture rise
   setup_ccp2(CCP_CAPTURE_RE); // Configure CCP2 to capture rise
   setup_ccp2(CCP_CAPTURE_DIV_4);
   setup_timer_1(T1_INTERNAL); // Start timer 1
   enable_interrupts(INT_CCP2); // Setup interrupt on falling edge
  enable_interrupts(INT_CCP1); // Setup interrupt on falling edge
  enable_interrupts(GLOBAL);
  a=0;
  while(TRUE) 
  {
    if(a==1)
    {
      period=value/5; //Doesn't need to divide if 4MHz
      if(period<1000)
      {
        freq=1000000/period;
        freq=freq/1000;
      }
      else
      {
        freq=1000000/period;
      }
 
      a=0;
    } 
  }
}
[/CODE]