Randomness

Ever since the 1950s, a function to generate a random number has been built into most computer systems. The earliest version of BASIC included such a function, the familiar RND command, which produced a "new and different random number" between 0 and 1 "each time it is used in a program" (39). As noted by the manual, however, each time a program was run, "the same sequence" of random numbers is generated. If a BASIC program generated a string of random digits such as 9, 0, 4, 1, 6, 4, it would produce the exact same numbers the next time the program ran. This lack of variation is an extreme example of what mathematicians call "pseudo-randomness"--a process or algorithm that appears to be random, but which, if left running long enough, will reveal itself to be a pattern. While the "pseudo" prefix would seem to denigrate this type of randomness as "not really" random, pseudo-randomness is generally acceptable, and in fact, desirable in many situations. For example, engineers running a computer simulation often need random variables, but they need those random variables ''to be the same'' with every run of the simulation; otherwise it is impossible to narrow down what process is actually being modeled in the simulation.

By the time of the Commodore 64, random number generation was more sophisticated than the original BASIC. The random numbers generated by the RND function on the Commodore 64 repeat themselves every 58,078 cycles--certainly a large enough that the pseudo-randomness is undetectable to the average observer. Because the random numbers begin repeating themselves after 58,078 cycles, the slashes that comprise the walls of the 10 PRINT maze begin repeating themselves after 58,078 times. After approximately 40,000 screenfuls, then, 10 PRINT begins to repeat itself.