Another method, used on CDC mainframes and some micros, can only be used if memory for a job is allocated contiguously as shown in Fig. 11.2.1 (and again in Fig. 11.5.2 below). Another register, the field length register, exists to compare the memory address generated by a program with the maximum address that this program can reach. If the generated address is less than, all is well. Otherwise, the program is trying to reach beyond the end of its memory and an error is signaled. Programs that suffer these errors are halted by the hardware and punished by the operating system.