The designation for more than 400 different digital logic integrated circuits, including NAND and NOR gates, inverters, buffers, decoders, frequency dividers, shift registers, flip-flops and binary adders. Introduced in the early 1960s by Texas Instruments for the first bipolar transistor-based TTL chips, the numbers are widely used by all manufacturers. CMOS versions of the 7400 series subsequently became available.