[Tutor] how to read one bit of a byte

Kent Johnson kent37 at tds.net
Wed Feb 21 14:05:54 CET 2007

Luke Paireepinart wrote:
> shawn bright wrote:
>> lo there all,
>> i am reading a binary file with open('myfile', 'rb')
>> then i do a read(1) to read one byte. cool so far.
>> but how do i read the individual bits of a byte
>> i mean if i have a = read(1)
>> how do i know what the msb of a is ?
>> i need to know because i have to see if the msb is set and i also need 
>> to know the value of the next bit.
> Well, you know the value of the MSB is...
> 1 2 4 8 16 32 64 128
> so if you divide the value by 128, and get a 1 and not a 0, then it's set.
> People commonly write functions to make binary lists from values.

This is also a good application of bitwise operations.

a & 128 will be 128 if the high bit in a is set, 0 if it is not.


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