Update comment to resolve ambiguity

[mahmudsudo]

The documentation is incorrect as the determinant for lower or upper case is the 5th bit not the 6th bit as written in the codebase.
An excerpt from the book the art of assembly language lays credence to this :
"Upper case characters always contain a zero in bit five; lower case alphabetic characters always contain a one in bit five. You
can use this fact to quickly convert between upper and lower case. If you have an upper
case character you can force it to lower case by setting bit five to one."

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[klensy]

For ref #118236

[slanterns]

Simply wrong. 'O' = 79 = 0b01001111, 'P' = 80 = 0b01010000. Don't rely on the book without actually checking it :)
(And if you read the code, it's also const ASCII_CASE_MASK: u8 = 0b0010_0000 masking the 6th bit.)

[mahmudsudo]

E = 0 1 0 0 0 1 0 1
e = 0 1 1 0 0 1 0 1
The bit that determines the case of an ascii letter is the FIFTH BIT counted from the low order bit , this is further explained in the example given above

[mahmudsudo]

Incase we are still not clear ,the low order bit is the rightmost bit ,it has a place value of zero , hence called the zero bit , any bit number is counted from the zero bit as origin .

[slanterns]

I get what makes you confused and apologize for my misunderstanding. However I just found that most people will call it the 6th bit by https://www.google.com/search?q=ascii+capital+bit+xor.

[mahmudsudo]

Simply wrong. 'O' = 79 = 0b01001111, 'P' = 80 = 0b01010000. Don't rely on the book without actually checking it. (And if you read the code, it's also const ASCII_CASE_MASK: u8 = 0b0010_0000 masking the 6th bit.)

nothing i said is actually wrong as pointed out by you ,
O = 01001111
o= 01101111
as shown the fifth bit (with the Low order bit as zero bit ) is the distinguishing factor not 6th bit )

[mahmudsudo]

I get what makes you confused. However I just found most people will call it the 6th bit by https://www.google.com/search?q=ascii+capital+bit+xor.

The usage by people doesnt make the counting standard
An 8 bit value is numbered X_0_ -- X_7_ even though there are 8 bits , the academia uses the fifth bit as the distinguisher between lowercase and uppercase .

[mahmudsudo]

Simply wrong. 'O' = 79 = 0b01001111, 'P' = 80 = 0b01010000. Don't rely on the book without actually checking it. (And if you read the code, it's also const ASCII_CASE_MASK: u8 = 0b0010_0000 masking the 6th bit.)

nothing i said is actually wrong as pointed out by you , O = 01001111 o= 01101111 as shown the fifth bit (with the Low order bit as zero bit ) is the distinguishing factor not 6th bit )

https://www.geeksforgeeks.org/program-toggle-characters-string/

[Teapot4195]

Honestly we shouldn't be arguing over whether to call it 5th or 6th bit, both are equally confusing unless a labeled byte diagram is provided both 5 and 6 are valid. If you really wanted to know which bit was being masked a quick google search would tell you which bit is being masked

[slanterns]

The usage by people doesnt make the counting standard

If you prefer standards, in ISO-IR-6: ASCII Graphic character set or ANSI INCITS 4-1986 they are called b1..b7 (since b8 is not used).
I feel arguing for things like that is just not so meaningful, and at least the comments are in a consistent state now while the edit will break it again :(

[Mark-Simulacrum]

r=me with suggestion or equivalent text applied and squashed into one commit. Otherwise I'm not inclined to change one number to the other; both seem equally not helpful to me.

[Teapot4195]

Squash please

[Dylan-DPC]

@mahmudsudo any updates on this?

[mahmudsudo]

I have resolved the suggested change to the commit

[Mark-Simulacrum]

This still needs to be squashed.

@rustbot author