The VCC, VSS, VDD, and VEE notation are use in naming the voltage at various common voltage power supply terminal only a wire that point between exist power source of specified circuit. It change these general voltage terms map to transistor technology.
This terminology originated in some way from the terminal of different type of transistor and their common connections to the logic circuit for example the VCC is often applied to BJT (Bipolar Junction Transistor) Collector, VEE to BJT (Bipolar Junction Transistor) EMITERS, VDD to FET (Field Effect Transistor) DRAINS and VSS to FET (Field Effect Transistor) SOURCE. This notation carries across to integrated circuits TTL (Transistor-Transistor Logic) ICs were originally based on BJT (Bipolar Junction Transistor) technology and so often use the VCC/VEE terminology CMOS (Complementary Metal-Oxide Semiconductor) IS are base on FET (Field Effect Transistor) technology.
The distinction between these common supply terms has been unclear by the interchangeable application of TTL and CMOS logic families most CMOS 74HC & AC IC if you open the datasheets it using VCC and GND designate the positive and negative supply pins.
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