Editing Action! (programming language) (section)

=== Example code ===
The following is example code for [[Sieve of Eratosthenes]] written in Action!. In order to increase performance, it disables the [[ANTIC]] graphics coprocessor, preventing its [[Direct memory access|DMA]] engine from "stealing" CPU cycles during computation.

 BYTE RTCLOK=20, ; addr of sys timer
      SDMCTL=559 ; DMA control
 
 BYTE ARRAY FLAGS(8190)
 
 CARD COUNT,I,K,PRIME,TIME
 
 PROC SIEVE()
 
   SDMCTL=0 ; shut off Antic
   RTCLOK=0 ; reset the clock to zero
 
   COUNT=0         ; init count
   FOR I=0 TO 8190 ; and flags
     DO
     FLAGS(I)='T ; "'T" is a compiler-provided constant for True
     OD
 
   FOR I=0 TO 8190 ; now run the sieve
     DO
     IF FLAGS(I)='T THEN
       PRIME=I+I+3
       K=I+PRIME
       WHILE K<=8190
         DO
         FLAGS(K)='F ; "'F" is a compiler-provided constant for False
         K==+PRIME
         OD
       COUNT==+1
     FI
     OD
   TIME=RTCLOK ; get timer reading
   SDMCTL=34   ; restore screen
 
   PRINTF("%E %U PRIMES IN",COUNT)
   PRINTF("%E %U JIFFIES",TIME)
 RETURN