Hex, decimal and binary
0x3C means nothing until you can see that it is 0011 1100 and that bit 0 is clear. The three conversions are one function call; the bits are the reason this is a page.
60
3C base 16 = 60 = 0x3C = 0b0011 1100
Decimal
60
Hex
0x3C
Octal
0o74
Binary
0011 1100
0x3C fits in 8 bits, with bits 5, 4, 3, 2 set. Hex is grouped in fours because each digit is exactly one nibble, which is why a datasheet writes a register as 0x3C and not as 60 — the digits line up with the bits and the decimal does not. This is also in the range a 7-bit I2C address lives in, if that is what you are holding.