74HC ICs are high-speed CMOS ICs that merge the low power consumption found in the 4000 series ICs with the better speed found in TTL IC’s. Basically, they are CMOS ICs with the same pin outs as the older 74LS series. The 74HCT series are a little different in that the 74HCT ICs can be mixed with the 74LS series ICs.