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Bitwise Shift in C and Arithmetic Shift

If x is a singed char. Does x >> n still the same as the integer division of 2^n and x << n same as the multiplication of 2^n?

Why does it work/not work?

How does arithmetic shift work?
Let's say if I have a signed char of 1001 in binary, -1 in decimal.
With an arithmetic right shift by 1 become 1100? Would it means -4 in decimal? so the multiplication we mentioned above won't work even for arithmetic shift.

Thanks!

Kocil

8 bit signed char
x = 10000001 in binary, -1 in decimal.
x << 1 = 00000010 = 2 in decimal
x >> 1 = 01000000 = 64 in decimal

So yeah, they don't work for negative number.
For positive number, they work

y = 00010000 in binary, 16 in decimal.
y << 1 = 00100000 = 32 in decimal
y >> 1 = 00001000 = 16 in decimal

until ...
y << 4 = 1000000 = ... you know how many it is, don't you

ASKER CERTIFIED SOLUTION

honey_hamster

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TriG

You're right honey_hamster, but you're shifting by 1 too many in your examples.

/2 ---> >> 1
/16 ---> >> 4

--tri

honey_hamster

Thanks TriG - I shifted the binary number the correct number, but for some reason I put the wrong number after the ">>". Oops.

jmcg

Nothing has happened on this question in more than 9 months. It's time for cleanup!

My recommendation, which I will post in the Cleanup topic area, is to
accept answer by honey_hamster.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

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