Rectification Notice of CS50: How does (buffer[3] & 0xf0) == 0xe0 work?

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I've created the above video because to answer the question of my students. I was doing it in a rush and I've inevitably made a mistake at 0:36. 

Below is what I wrote. 

0xe0 = 1110 0000
0xe1 = 1110 0001
0xe2 = 1110 0010
0xe3 = 1110 0011
0xe4 = 1110 0100
0xe5 = 1110 0101
0xe6 = 1110 0110
0xe7 = 1110 0111
0xe8 = 1110 1000
0xe9 = 1110 1001
0xea = 1110 1010
0xeb = 1110 1011
0xec = 1110 1100
0xed = 1110 1101
0xef = 1110 1110

I've made a mistake. I've skipped 0xee which is 1110 1110. The correct sequence is as below. 

0xe0 = 1110 0000
0xe1 = 1110 0001
0xe2 = 1110 0010
0xe3 = 1110 0011
0xe4 = 1110 0100
0xe5 = 1110 0101
0xe6 = 1110 0110
0xe7 = 1110 0111
0xe8 = 1110 1000
0xe9 = 1110 1001
0xea = 1110 1010
0xeb = 1110 1011
0xec = 1110 1100
0xed = 1110 1101
0xee = 1110 1110
0xef = 1110 1111

I am sorry for my careless mistake and special thanks to Bonnie Tseng for pointing it out. 

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