View tc74hc257p datasheet:

TC74HC257P IL08D C-MOS 2-LINE-TO-1-LINE DATA SELECTOR/MULTIPLEXER —TOP VIEW— INH Y0 Y1 YC X0 X1 XC IN IN IN OUT IN IN OUT 2 V0 16 15 14 13 12 11 10 9 3 V1 VC 4 VDD OPEN 5 W0 6 W1 WC 7 OPEN 11 X0 10 X1 XC 9 GND 1 2 3 4 5 6 7 8 OPEN 14 Y0 A V0 V1 VC W0 W1 WC 13 Y1 YC 12 IN IN IN OUT IN IN OUT OPEN A INH CONT. IN ON 1 15 INH A CHANNEL 0 0 0 0 : LOW LEVEL 0 1 1 1 : HIGH LEVEL 1 x OPEN x : DON’T CARE