$ZCYC(string) computes and returns the cyclical-redundancy check value for the string. It allows two intercommunicating programs to check for data integrity.
The sending program transmits a piece of data along with a matching check value that it calculates using $ZCYC. The receiving program verifies the transmitted data by using $ZCYC to calculate its check value. If the two check values match, the received data is the same as the sent data.
$ZCYC calculates the check value by performing an exclusive OR (XOR) on the binary representations of all the characters in the string.
Note that the $ZCYC value of an 8-bit string is identical to the $ZCRC mode 1 value.
A string. Can be specified as a value, a variable, or an expression. String values are enclosed in quotation marks.
In this example, the first $ZCYC returns 65; the second returns 3; and the third returns 64.
SET x= $ZCYC("A") ; 1000001 (only one character; no XOR ) SET y= $ZCYC("AB") ; 1000001 XOR 1000010 -> 0000011 SET z= $ZCYC("ABC") ; 1000001 XOR 1000010 -> 0000011 | 1000011 -> 100000 WRITE !,"x=",x," y=",y," z=",z