Here's an example of a BASIC program that calculates the square root of numbers from 20 to 64:
10 FOR I = 20 TO 64
20 S = SQR(I)
30 PRINT "The square root of "; I; " is "; S
40 NEXT I
This program uses a FOR loop to iterate through the numbers from 20 to 64. For each number, it calculates the square root using the SQR function and then prints out the result using the PRINT statement. The program uses a variable S to store the square root value.