Traditional programmable logic devices (PLD) and field programmable gate arrays allow circuit designers to implement logic circuits with fewer chips relative to standard gate level designs based on primitive gates and flip-flops. Design changes do not require physical changes to the printed circuit board as long as the revised functions fit onto the same programmable chip. The low cost of design revisions makes programmable chips very attractive for prototype design and low volume production. Designers often move up the design ladder once proven designs move into high volume production. Companies produce PLD devices in different technologies to meet varying design and market demands. "Programming technology” refers to the physics of chip programming and affects ease of programming and the ability to reprogram or to reconfigure chips. The dominant technologies in PLD devices are bipolar and CMOS. The programming technologies used in PLDs are virtually the same as the programming technologies available for read-only memories.