[Question]
  [
# Introduction
[The Nineteenth Byte](https://chat.stackexchange.com/rooms/240/the-nineteenth-byte) is [CGCC](https://codegolf.stackexchange.com)'s official chatroom (go check it out!). Its name is a play on [the nineteenth hole](https://en.wikipedia.org/wiki/Nineteenth_hole), and it also refers to golf, which is appropriate for [CGCC](https://codegolf.stackexchange.com)'s chatroom's name. The name is also precisely \$19\$ bytes long, as its name states.
# Challenge
Your task is to write a program that outputs `Stack Exchange Chat - The Nineteenth Byte` exactly. However, if the nineteenth byte and only the nineteenth byte of your source code is removed, it should output only `Stack Exchange Chat`. Because of this, the best score you can get will be \$19\$ bytes. For example, if your code is `abcdefghijklmnopqrstuvwxyz`, then `abcdefghijklmnopqrstuvwxyz` must output `Stack Exchange Chat - The Nineteenth Byte` and `abcdefghijklmnopqrtuvwxyz` must output `Stack Exchange Chat`.
# Rules
* [Standard loopholes](https://codegolf.meta.stackexchange.com/questions/1061/loopholes-that-are-forbidden-by-default) are forbidden.
* Trailing whitespace is allowed.
* If possible, please link to an online interpreter (e.g. [TIO](https://tio.run)) to run your program on.
* Please explain your answer. This is not necessary, but it makes it easier for others to understand.
* Languages newer than the question are allowed. This means you could create your own language where it would be trivial to do this, but don't expect any upvotes.
* You are scored by the length of the program that outputs `Stack Exchange Chat - The Nineteenth Byte`.
* This is [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'"), so shortest code in bytes wins!
  
[Answer]
# [Jelly](https://github.com/DennisMitchell/jelly), 25 bytes
```
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°‚Å∏¬¢6·πÖ»Ø*·ªµ#K¬ªi∆á‚Äùh
```
[Try it online!](https://tio.run/##y0rNyan8//9Rw5xDC0OOTbQ8stHo4c62IDD/UeOOQ4vMHu5sPbFe6@Hurcreh3ZnHmt/1DA34/@hRf8B "Jelly ‚Äì Try It Online") or [Try it without `#`](https://tio.run/##y0rNyan8//9Rw5xDC0OOTbQ8stHo4c62IDD/UeOOQ4vMHu5sPbFe6@Hurd6Hdmcea3/UMDfj/6FF/wE)
# [Jelly](https://github.com/DennisMitchell/jelly), 25 bytes
```
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°T·∏üKY=…±√∏~¬ªt∆ë∆á‚Å∂K
```
[Try it online!](https://tio.run/##y0rNyan8//9Rw5xDC0OOTbQ8stHo4c62IAj/4Y753pG2Jzce3lF3aHfJsYnH2h81bvP@f2jRfwA "Jelly ‚Äì Try It Online") or [Try it without `~`](https://tio.run/##y0rNyan8//9Rw5xDC0OOTbQ8stHo4c62IAj/4Y753pG2Jzce3nFod8mxicfaHzVu8/5/aNF/AA)
## How they work
```
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°‚Å∏¬¢6·πÖ»Ø*·ªµ#K¬ªi∆á‚Äùh - Main link. No arguments
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°‚Å∏¬¢6·πÖ»Ø*·ªµ#K¬ª     - Pair of compressed strings ["Stack Exchange Chat", " - The Nineteenth Byte"]
                      ∆á   - Keep those for which the following is True:
                     i ‚Äùh - They contain "h"; ["Stack Exchange Chat", " - The Nineteenth Byte"]
                            Smash together and output
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°‚Å∏¬¢6·πÖ»Ø*·ªµK¬ªi∆á‚Äùh  - Main link. No arguments
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°‚Å∏¬¢6·πÖ»Ø*·ªµK¬ª      - Pair of compressed strings ["Stack Exchange Chat", "^Backets reamyappenzell"]
                     ∆á    - Keep those for which the following is True:
                    i ‚Äùh  - They contain "h"; ["Stack Exchange Chat"]
                            Smash together and output
```
And the second one:
```
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°T·∏üKY=…±√∏~¬ªt∆ë∆á‚Å∂K - Main link. No arguments
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°T·∏üKY=…±√∏~¬ª      - Pair of compressed strings ["Stack Exchange Chat", "- The Nineteenth Byte"]
                     ∆ë∆á   - Keep those where the following has no effect:
                    t  ‚Å∂  -   Removing spaces from the front and end; ["Stack Exchange Chat", "- The Nineteenth Byte"]
                        K - Join with spaces; "Stack Exchange Chat - The Nineteenth Byte"
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°T·∏üKY=…±√∏¬ªt∆ë∆á‚Å∂K  - Main link. No arguments
‚Äú¬°T∆ë9ƒ±2·πÜR‚Äú¬°T·∏üKY=…±√∏¬ª       - Pair of compressed strings ["Stack Exchange Chat", " Backets reamyappenzell"]
                    ∆ë∆á    - Keep those where the following has no effect:
                   t  ‚Å∂   -   Removing spaces from the front and end; ["Stack Exchange Chat"]
                       K  - Join with spaces; "Stack Exchange Chat"
```
[Answer]
# [Jelly](https://github.com/DennisMitchell/jelly), ~~25~~ 24 bytes
```
‚Äú√Ü√ß∆≤Bn∆•·∫à·πõ‚±Æ_·ª¥»∑O·πò·ªµ·∏äƒä¬ª¬ª·∏£19$
```
[Try it online!](https://tio.run/##ATsAxP9qZWxsef//4oCcw4bDp8ayQm7GpeG6iOG5m@Kxrl/hu7TIt0/huZjhu7XhuIrEisK7wrvhuKMxOST//w "Jelly ‚Äì Try It Online")
## Without the nineteenth byte
```
‚Äú√Ü√ß∆≤Bn∆•·∫à·πõ‚±Æ_·ª¥»∑O·πò·ªµ·∏äƒä¬ª·∏£19$
```
[Try it online!](https://tio.run/##ATkAxv9qZWxsef//4oCcw4bDp8ayQm7GpeG6iOG5m@Kxrl/hu7TIt0/huZjhu7XhuIrEisK74bijMTkk//8 "Jelly ‚Äì Try It Online")
It works no matter if you index from 0 or 1!
## Explanation
```
‚Äú√Ü√ß∆≤Bn∆•·∫à·πõ‚±Æ_·ª¥»∑O·πò·ªµ·∏äƒä¬ª¬ª·∏£19$   Main niladic link
‚Äú√Ü√ß∆≤Bn∆•·∫à·πõ‚±Æ_·ª¥»∑O·πò·ªµ·∏äƒä¬ª        "Stack Exchange Chat - The Nineteenth Byte"
                   ¬ª       [Calculate the byte-wise maximum with]*
                       $   (
                    ·∏£19      Get the first 19 characters
                       $   )
```
\*When indexing from 1, it's actually the first `¬ª` that is removed, but the result is the same.
[Answer]
# [JavaScript (V8)](https://v8.dev/), 66 bytes
The nineteenth byte is the `X`.
```
print("Stack",(s="X"&&" - The Nineteenth Byte","Exchange Chat"+s))
```
[Try it online!](https://tio.run/##BcGxCoAgEADQXzluECXdW1qK1pYaWg850gIRPaS@3t67qVH1JWZxbew9l5hE4y7kH7S6TniiUggOjsCwxcTCnCTA/AmjxfX1gdLFsAQSHKoxvf8 "JavaScript (V8) ‚Äì Try It Online")
[Try it online!](https://tio.run/##BcHBCoAgDADQXxk7hJLeu3QpunapHxgy0gIRHVJfv967qVMLNRXxfVItNWUxeAiFB51pM@IwIHg4I8OeMgtzlgjLJ4wOtzdEyhfDGklwbNaq/g "JavaScript (V8) ‚Äì Try It Online") (nineteenth byte removed)
### Commented
```
print(                            // print:
  "Stack",                        //   the first word followed by an implicit space
  (                               //
    s = "X" &&                    //   define s as either " - The Nineteenth Byte"
        " - The Nineteenth Byte", //   or an empty string if the 'X' is removed
    "Exchange Chat" + s           //   append "Exchange Chat" followed by s
  )                               //
)                                 // end
```
[Answer]
# [Python 2](https://docs.python.org/2/), 66 bytes
```
s,y='Stack Exch',01
print s+'ange Chat'+' - The Nineteenth Byte'*y
```
[Try it online!](https://tio.run/##K6gsycjPM/r/v1in0lY9uCQxOVvBtSI5Q13HwJCroCgzr0ShWFs9MS89VcE5I7FEXVtdQVchJCNVwS8zL7UkNTWvJEPBqbIkVV2r8v9/AA "Python 2 ‚Äì Try It Online")
Not really a smart answer. :p
The nineteenth byte here is the `1`.
y is `0` or `1` depending on if the nineteenth byte is removed.
*thanks to pxeger for -2 bytes*
[Answer]
# [Zsh](https://www.zsh.org/), 54 bytes
```
set Exchange Chat \
- The Nineteenth Byte
<<<Stack\ $@
```
[Try it online!](https://tio.run/##qyrO@P@/OLVEwbUiOSMxLz1VwTkjsUQhhktXISQjVcEvMy@1JDU1ryRDwamyJJXLxsYmuCQxOTtGQcXh/38A "Zsh ‚Äì Try It Online")
`set` assigns the given words to the default variable `$@`. As with the previous one, `\` joins the two lines into one call to set, instead of treating `- The Nineteenth Byte` as a command (which does nothing).
---
## [Zsh](https://www.zsh.org/), 55 bytes
```
1=" Exchange Chat"\
" - The Nineteenth Byte"
<<<Stack$1
```
[Try it online!](https://tio.run/##qyrO@P/f0FZJwbUiOSMxLz1VwTkjsUQphktJQVchJCNVwS8zL7UkNTWvJEPBqbIkVYnLxsYmuCQxOVvF8P9/AA "Zsh ‚Äì Try It Online")
Idea boringly copied from [@xnor's genius answer](https://codegolf.stackexchange.com/a/221334). The `\` escapes the newline, which concatenates the two strings; without it, the second line is ignored as an undefined command.
---
## [Zsh](https://www.zsh.org/), 58 bytes
```
1=Stack\ Exchang
2=" - The Nineteenth Byte"
<<<$1e\ Chat$2
```
[Try it online!](https://tio.run/##qyrO@P/f0Da4JDE5O0bBtSI5IzEvncvIVklBVyEkI1XBLzMvtSQ1Na8kQ8GpsiRVicvGxkbFMDVGwTkjsUTF6P9/AA "Zsh ‚Äì Try It Online")
The 19th byte is the second `=`, which changes that line from a variable assignment to an undefined command which does nothing. Then, when printing, `$2` defaults to empty.
[Answer]
# [Emotion](https://github.com/Quantum64/Emotion), 34 [bytes](https://quantum64.github.io/EmotionBuilds/1.1.0///?state=JTdCJTIybW9kZSUyMiUzQSUyMmNvZGVwYWdlJTIyJTdE)
```
üòáüòòüßñüöµüßñüí´üòãüßñüíôü§ôüíÅü§π‚òùüçìüßñüíñüç∏üòöü§ïüòîüòòüòâüíöüôåüôéü••ü§§üë®ü§ëüíáüë±üíîüòØüò®
```
The nineteenth byte is ü§ï.
[Try it online!](https://quantum64.github.io/EmotionBuilds/1.1.0///?state=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)
[Answer]
# [C (gcc)](https://gcc.gnu.org/), 69 bytes
Without the removal of the 19th byte, the full string (which is much less than 119 characters) is printed; if the 19th byte is removed, only 19 characters are printed instead.
```
main(){printf("%.119s","Stack Exchange Chat - The Nineteenth Byte");}
```
[Try it online!](https://tio.run/##S9ZNT07@/z83MTNPQ7O6oCgzryRNQ0lVz9DQslhJRym4JDE5W8G1IjkjMS89VcE5I7FEQVchJCNVwS8zL7UkNTWvJEPBqbIkVUnTuvb/fwA "C (gcc) ‚Äì Try It Online")
With the 19th byte removed: [Try it online!](https://tio.run/##S9ZNT07@/z83MTNPQ7O6oCgzryRNQ0lVz9CyWElHKbgkMTlbwbUiOSMxLz1VwTkjsURBVyEkI1XBLzMvtSQ1Na8kQ8GpsiRVSdO69v9/AA "C (gcc) ‚Äì Try It Online")
[Answer]
# [Python 2](https://docs.python.org/2/), 58 bytes
```
s="Exchange Chat "\
"- The Nineteenth Byte"
print"Stack",s
```
[Try it online!](https://tio.run/##K6gsycjPM/r/v9hWybUiOSMxLz1VwTkjsURBKYZLSVchJCNVwS8zL7UkNTWvJEPBqbIkVYmroCgzr0QpuCQxOVtJp/j/fwA "Python 2 ‚Äì Try It Online") ([no 19th byte](https://tio.run/##K6gsycjPM/r/v9hWybUiOSMxLz1VwTkjsURBiUtJVyEkI1XBLzMvtSQ1Na8kQ8GpsiRViaugKDOvRCm4JDE5W0mn@P9/AA "Python 2 ‚Äì Try It Online"))
The 19th byte is the `\` at the end of the first line. It acts as a line continuation character to make the full line be `"Exchange Chat ""- The Nineteenth Byte"` using Python's automatic concatenation of adjacent string literals.
Without the `\`, the line ends there, and the second line is lonely string value that doesn't do anything. The truncated string ends in a space, which is fine because the challenge allows for trailing whitespace.
---
**[Python 2](https://docs.python.org/2/), 61 bytes**
```
s="Exchange Chat"+--1*" - The Nineteenth Byte"
print"Stack",s
```
[Try it online!](https://tio.run/##K6gsycjPM/r/v9hWybUiOSMxLz1VwTkjsURJW1fXUEtJQVchJCNVwS8zL7UkNTWvJEPBqbIkVYmroCgzr0QpuCQxOVtJp/j/fwA "Python 2 ‚Äì Try It Online") ([no 19th byte](https://tio.run/##K6gsycjPM/r/v9hWybUiOSMxLz1VwTkjsURJW9dQS0lBVyEkI1XBLzMvtSQ1Na8kQ8GpsiRViaugKDOvRCm4JDE5W0mn@P9/AA "Python 2 ‚Äì Try It Online"))
The 19th byte is a `-`. Originally we append `--1` (so, `1`) copies of the string `" - The Nineteenth Byte"`, with the 19th byte is removed, this is `-1` copies which is nothing.
[Answer]
# [Husk](https://github.com/barbuz/Husk), ~~25~~ 23 bytes
```
Œ£√ºL¬Ω¬®·∏üK»¶Œû√óƒóC»ßt-Œæ·∏ü%NhŒ≤/y
```
[Try it online!](https://tio.run/##AS4A0f9odXNr///Oo8O8TMK9wqjhuJ9LyKbOnsOXxJdDyKd0Lc6@4bifJU5ozrIvef// "Husk ‚Äì Try It Online")
[Try it online without the 19th byte!](https://tio.run/##AS0A0v9odXNr///Oo8O8TMK9wqjhuJ9LyKbOnsOXxJdDyKd0Lc6@4bifJWjOsi95//8 "Husk ‚Äì Try It Online")
### Explanation
`¬®·∏üK»¶Œû√óƒóC»ßt-Œæ·∏ü%NhŒ≤/y` is a compressed string, equivalent to `"Stack Exchange Chat - The Nineteenth Byte"`. If we remove `N` (the nineteenth byte of the program) we get `¬®·∏üK»¶Œû√óƒóC»ßt-Œæ·∏ü%hŒ≤/y`, which is equivalent to `"Stack Exchange Chat - Thefischer\n Byte"` (`\n` being a newline character).
Now, starting from one of these two strings:
```
  "Stack Exchange Chat - The Nineteenth Byte"    "Stack Exchange Chat - Thefischer\n Byte"
¬Ω   Split the string in half
  ["Stack Exchange Chat -",                      ["Stack Exchange Chat",
   " The Nineteenth Byte"]                        " - Thefischer\n Byte"]
√ºL   nub by length: remove strings with the same length as previous ones
  ["Stack Exchange Chat -",                      ["Stack Exchange Chat"]
   " The Nineteenth Byte"]
Œ£   Join the strings together
  "Stack Exchange Chat - The Nineteenth Byte"    "Stack Exchange Chat" 
```
[Answer]
# Scala 3, 90 bytes
```
val x="Stack Ex"+a/*/ */+" - The Nineteenth Byte"
def a="change Chat"
@main def m=print(x)
```
[Try it in Scastie!](https://scastie.scala-lang.org/RIMt9dBVSaGLXFopkJpO3Q)
With the nineteenth byte removed:
```
val x="Stack Ex"+a// */+" - The Nineteenth Byte"
def a="change Chat"
@main def m=print(x)
```
[Try it in Scastie!](https://scastie.scala-lang.org/dlYCNGoWRmCBsKFUxvUclw)
The syntax highlighting should show what happens. This would be a byte shorter in a language without nested comments, since the space in `/*/ */` wouldn't be needed, but I just like Scala :P
A possible solution with a newline that doesn't work because of parsing rules:
```
val x="Stack E"+a//
+" - The Nineteenth Byte"
def a="xchange Chat"
@main def m=print(x)
```
[Answer]
# [Python 2](https://docs.python.org/2/), 65 bytes
```
b='Stack Excha'
n=88
print b+'nge Chat - The Nineteenth Byte'[:n]
```
**[Try all of it](https://tio.run/##K6gsycjPM/r/P8lWPbgkMTlbwbUiOSNRnSvP1sKCq6AoM69EIUlbPS89VcE5I7FEQVchJCNVwS8zL7UkNTWvJEPBqbIkVT3aKi/2/38A "Python 2 ‚Äì Try It Online")**  
**[Try it without the 19th byte](https://tio.run/##K6gsycjPM/r/P8lWPbgkMTlbwbUiOSNRnSvP1oKroCgzr0QhSVs9Lz1VwTkjsURBVyEkI1XBLzMvtSQ1Na8kQ8GpsiRVPdoqL/b/fwA "Python 2 ‚Äì Try It Online")**
Works in Python 3 trivially for [66 bytes](https://tio.run/##K6gsycjPM7YoKPr/P8lWPbgkMTlbwbUiOSNRnSvP1sKCq6AoM69EI0lbPS89VcE5I7FEQVchJCNVwS8zL7UkNTWvJEPBqbIkVT3aKi9W8/9/AA "Python 3.8 ‚Äì Try It Online")
[Answer]
# Scratch 3.0, 10 blocks/160 bytes
```
define
set[outpuuut v]to[Stack Exchange Chat - The Nineteenth Byte
set[outpuuu v]to[Stack Exchange Chat
if<(outpuuut)>(0)>then
say(outpuuut
else
say(outpuuu
end
```
This outputs `Stack Exchange Chat - The Nineteenth Byte`
Because Scratch is a block-based language, it may not seem obvious on how to remove a byte at first. But thankfully, there exists a text format called ScratchBlocks which [we seem to allow for scoring](https://codegolf.meta.stackexchange.com/a/5013/78850). The above ScratchBlocks corresponds to the following real blocks:
[![This actually wasn't as painful as I thought it'd be](https://i.stack.imgur.com/FvKCN.png)](https://i.stack.imgur.com/FvKCN.png)
[Try it on Scratch!](https://scratch.mit.edu/projects/506212911/)
Removing the 19th byte of this program gives
```
define
set[outpuuu v]to[Stack Exchange Chat - The Nineteenth Byte
set[outpuuu v]to[Stack Exchange Chat
if<(outpuuut)>(0)>then
say(outpuuut
else
say(outpuuu
end
```
This outputs `Stack Exchange Chat`
[![enter image description here](https://i.stack.imgur.com/Pt11k.png)](https://i.stack.imgur.com/Pt11k.png)
[Try it on Scratch!](https://scratch.mit.edu/projects/506216881/)
Explanation coming soon
[Answer]
# [Python 3.8 (pre-release)](https://docs.python.org/3.8/), 72 bytes
```
print('Stack Exch{1}'.format(x:='ange Chat',x+' - The Nineteenth Byte'))
```
[Try it online!](https://tio.run/##K6gsycjPM7YoKPr/v6AoM69EQz24JDE5W8G1Ijmj2rBWXS8tvyg3sUSjwspWPTEvPVXBOSOxRF2nQltdQVchJCNVwS8zL7UkNTWvJEPBqbIkVV1T8/9/AA "Python 3.8 (pre-release) ‚Äì Try It Online")
Different approach than @ManishKundu solution
Nineteenth byte is `1` removing it will result `0` to only suffix `hange Chat`
Thanks to @ZaelinGoodman for insight
-6 bytes to @Makonede
[Answer]
# [><>](https://esolangs.org/wiki/Fish), 62 bytes
```
"Stack Exch"\" - "<
" tahC egna"/r>o<r/
eeteniN ehT"\"etyB htn
```
[Try it online!](https://tio.run/##S8sszvj/Xym4JDE5W8G1IjlDKUZJQVdByYZLSaEkMcNZITU9L1FJv8gu36ZInys1tSQ1L9NPITUjBKgutaTSSSGjJO//fwA "><> ‚Äì Try It Online")
[Try it without the Nineteenth byte](https://tio.run/##S8sszvj/Xym4JDE5W8G1IjlDKUZJQVdBiUtJoSQxw1khNT0vUUm/yC7fpkifKzW1JDUv008hNSMEqCy1pNJJIaMk7/9/AA "><> ‚Äì Try It Online")
I've been playing around with ><> this week and this one was kind of a freebie, although it still turned out to be an interesting packing problem that ended up getting quite lucky at the end.
The Nineteenth byte is unsurprisingly the `<` at the end of the first row. With or without it, we'll execute `"Stack Exchange Chat "`, pushing that string onto the stack (in reverse order; usually we want to push strings backwards but here it's convenient to start with the prefix so we'll just reverse the stack later instead).
At this point, the program encounters the `/` at the end of the second row, hitting it from the right and heading down, *conveniently going through the space between "Nineteenth" and "Byte"*, then wrapping around vertically and either heading leftwards on the first or second row. With the `<`, we execute `"The Nineteenth Byte"`, pushing that string on the stack and then head to the output gadget, and without it we head directly to the output.
The output is done by first reversing the stack with `r`, and then heading into the bottomless pit of `>o<` which executes the output instruction `o` endlessly until the stack is emptied and the program exits via error.
[Answer]
# [Factor](https://factorcode.org/), ~~95 94~~ 87 bytes
Saved 1 precious byte thanks to @OriginalOriginalOriginalVI!
Saved 7 more bytes thanks to @Bubbler!
```
"Stack Exchange C"f " - The Nineteenth Byte""hat"rot [ prepend nip ] [ glue ] if* print
```
[Try it online!](https://tio.run/##HY0xDsIwEAS/sroSiQ9AB0KIJk2giigss46tRBfjXCTyehPoZpqZ4LxNpT7aW3M9YGBRjsiFZmsuSQ0z3wvVc0aacKzSmvMDLh8fnfbEWQIEe9wj0SSlkWoRp9UoEp1JmQzdr5ipL2jKeG7ejws3SGGH/6bWLw "Factor ‚Äì Try It Online")
Explained:
```
"Stack Exchange C"f " - The Nineteenth Byte""hat"  ! push items on the stack,
                                                   ! f (false) value is 19th char
rot                                                ! rotate, f now at top of stack
                                                   ! if f is missing, "Stack Exchange C"
                                                   ! is at the top
[ prepend nip ] [ glue] if* print                  ! if* f is found, glue the strings and print.
                                                   ! if* a string is found, it is considered to
                                                   ! be true, retain it on the stack, swap & glue
                                                   ! the top strings, drop the "19th Byte" string,
                                                   ! append and print.
```
Old version:
```
"Stack Exchange C"f "hat"" - The Nineteenth Byte"rot [ nip swap append ] [ 3append ] if* print
```
[Try it online!](https://tio.run/##Pc2xCgIxEEXRX3mkFKzstFNEbLZZrcRiiC8mrMxmkxHdr49iYXc5zQ3ibSzt3B@7wxoDi/KBXGg255LUUDk9qZ4VacSmud7ED9i/fRS9EzsX4KKYc1jiFIkuKY1Ui9jORldGwwWaMupLMiRn6g3Xr63@ncICv1trHw "Factor ‚Äì Try It Online")
Explained:
```
"Stack Exchange C"f "hat"" - The Nineteenth Byte"  ! push items on the stack,
                                                   ! f (false) value is 19th char
rot                                                ! rotate, f now at top of stack
                                                   ! if f is missing, "Stack Exchange C"
                                                   ! is at the top
[ nip swap append ] [ 3append ] if* print          ! if* f is found, append the strings and print.
                                                   ! if* a string is found, it is considered to
                                                   ! be true, retain it on the stack, drop the
                                                   ! "19th Byte" string, swap stack strings,
                                                   ! append and print.
```
[Answer]
# PowerShell 7, 60 bytes
```
'Stack Exchange'+(!0 ?' Chat - The Nineteenth Byte':' Chat')
#                 ^
#                 19th byte
```
No TIO because the ternary operator is not supported in powershell 6 and below
## Alternate Solutions
### PowerShell 7, 60 bytes
```
"Stack Exchan$($x=!0 ?' - The Nineteenth Byte':'')ge Chat$x"
#                 ^
#                 19th byte
```
### PowerShell, 61 58 bytes
-3 bytes thanks to @mazzy!!
```
"Stack Exchange {01}"-f'Chat','Chat - The Nineteenth Byte'
#                 ^
#                 19th byte
```
[Try it online!](https://tio.run/##K8gvTy0qzkjNydFNzi9K/f9fKbgkMTlbwbUiOSMxLz1VodrAsFZJN03dOSOxRF0HTCnoKoRkpCr4ZeallqSm5pVkKDhVlqSqc2FqJVLn//8A)
[Answer]
# [SNOBOL4 (CSNOBOL4)](http://www.snobol4.org/csnobol4/), 90 bytes
```
              Y =1
	X =GT(Y) ' - The Nineteenth Byte'
	OUTPUT ='Stack Exchange Chat' X
END
```
[Try it online!](https://tio.run/##VcGxDkAwFAXQuf2Ku5XBILF2QWNDohLGkhcVUoM38PU1O@cO13KdRYz4maFzKSboxiZzCoUM1hPaPRATBfYoXyYlRTfafrTQamC3HjDP6l3YCJV3rDBJ09Yxfg "SNOBOL4 (CSNOBOL4) ‚Äì Try It Online")
The nineteenth byte here is the `1`. SNOBOL treats an empty string as `0`, and an empty right-hand assignment as an empty string. So when the byte is removed, the program assigns a value of `0` to `Y`, and the comparison `Y GT` (implicit 0) fails, hence `X` is assigned an empty value as well.
[Answer]
# [05AB1E](https://github.com/Adriandmen/05AB1E), 27 bytes
```
‚Äù -‚Ç¨‚Ç¨¬•≈†teenth√Ñ√Å‚Äù √µs‚Äù√Ç‚Äö‚Äπ¬∫≈†√Ü√ø
```
[Try it online!](https://tio.run/##yy9OTMpM/f//UcNcBd1HTWuA6NDSowtKUlPzSjIOtxxuBEkc3loMpA43PWqY9ahh56FdRxccbju8//9/AA "05AB1E ‚Äì Try It Online") and [Try it without `s`](https://tio.run/##yy9OTMpM/f//UcNcBd1HTWuA6NDSowtKUlPzSjIOtxxuBEkc3gokDzc9apj1qGHnoV1HFxxuO7z//38A)
```
‚Äù -‚Ç¨‚Ç¨¬•≈†teenth√Ñ√Å‚Äù # Compressed string " - The Nineteenth Byte"
 √µ               # push the empty string
 (s)             # (swap back to the other string)
   ‚Äù√Ç‚Äö‚Äπ¬∫≈†√Ü√ø      # push compressed string "Stack Exchange Chat√ø"
                 # where √ø is replaced by the string on the top of the stack
```
[Answer]
# Java, ~~104~~ ~~83~~ 72 bytes
```
$->"Stack ExchangeA Chat".replaceAll("A(.*)","$1 - The Nineteenth Byte")
```
The nineteenth byte is `A`.
*Saved 21 bytes thanks to [79037662](https://codegolf.stackexchange.com/users/89930).*
*Saved 11 bytes thanks to [Olivier Gr√©goire](https://codegolf.stackexchange.com/users/16236).*
[Try it online!](https://tio.run/##PU09a8MwEN3zKw6RQSqxoHPagBOSLV1cuoQOV0W25VxkYZ1CTclvd1Vi@pb3uHsfHd6w6M6XKaQvcgYMYYxwROfhZwEZ8z0ycqZb785wzV9Z8eB8c/oEHJqoZvMfutyoEzvSdfKGXe/1YRYvHzm@eiQ3UL9Oy2IjKkZzgf23adE3toRdiyz0YAOhsSWRFKXUT0qsxPIZCnhvLbw5b9lazy1sR7ZCTev/@WqMbK@6T6xD3mHystYYAo3SJyKlHtb74j79Ag)
[Try it online (without the nineteenth byte)!](https://tio.run/##PU09T8MwEN37K05WBxs1lpiBSi2CDZYgFsRwuJfE6dWx4nNFhPrbg1Ej3vKe7t5Hj2es@sNxjvmLvQPHmBK8oA/ws4KC5Z4EpdB58Ac4la@uZfSh/fgEHNtkFvMf@tJos3i2TQ5O/BDs8yLu30t8c01uoXmY19VW1YLuCE/frsPQEjx2KMqOFBkd7Zi12ml7Y9RGrW@hgreO4NUHEqIgHewnIWXmu//1ekpCJztksbHMCAfdWIyRJx0yszFX62V1mX8B)
[Answer]
# [shortC](https://github.com/aaronryank/shortC), 54 bytes
```
Ds"Exchange Chat\x20- The Nineteenth Byte"
AJ"Stack "s
```
[Try it online!](https://tio.run/##K87ILypJ/v/fpVjJtSI5IzEvPVXBOSOxJKbCyEBXISQjVcEvMy@1JDU1ryRDwamyJFWJy9FLKbgkMTlbQan4/39DAA "shortC ‚Äì Try It Online")
### Without the Nineteenth byte
```
Ds"Exchange Chat\x0- The Nineteenth Byte"
AJ"Stack "s
```
[Try it online!](https://tio.run/##K87ILypJ/v/fpVjJtSI5IzEvPVXBOSOxJKbCQFchJCNVwS8zL7UkNTWvJEPBqbIkVYnL0UspuCQxOVtBqfj/f0MA "shortC ‚Äì Try It Online")
`\x20` denotes a space character, removing the `2` we get `\x0` (null character) which in C is the string terminator.
[Answer]
# [R](https://www.r-project.org/), ~~72~~ ~~68~~ 63 bytes
-4 bytes thanks to Dominic van Essen.
```
cat(scan(,"",3+0004))
Stack Exchange Chat - The Nineteenth Byte
```
[Try it online!](https://tio.run/##K/r/PzmxRKM4OTFPQ0dJScdY28DAwERTkyu4JDE5W8G1IjkjMS89VcE5I7FEQVchJCNVwS8zL7UkNTWvJEPBqbIk9f9/AA "R ‚Äì Try It Online")
The 19th byte is the `4`. In the unaltered version, `scan` will read 7 words from the next line, and then print them. If you remove the `4`, `scan` will read only 3 words and then print them.
[Answer]
# Excel, ~~73~~ 70 bytes
*Updated thanks to @EngineeringToast*
```
=LET(a,"Stack ",b,1,a&"Exchange Chat"&IF(b," - The Nineteenth Byte",))
```
*Original*
```
=LET(s,"Sta",n,30--11,LEFT(s&"ck Exchange Chat - The Nineteenth Byte",n))
```
Shows all characters as is; the left 19 characters if the 19th byte (-) is deleted.
[Answer]
# [Foo](https://esolangs.org/wiki/Foo), 46 bytes
```
"Stack Exchange Ch"at"at - The Nineteenth Byte
```
[Try it online!](https://tio.run/##S8vP//9fKbgkMTlbwbUiOSMxLz1VwTlDKbEEiBR0FUIyUhX8MvNSS1JT80oyFJwqS1L//wcA "Foo ‚Äì Try It Online")
[Try it online!](https://tio.run/##S8vP//9fKbgkMTlbwbUiOSMxLz1VwTkjsUQpsURBVyEkI1XBLzMvtSQ1Na8kQ8GpsiT1/38A "Foo ‚Äì Try It Online")
Output the quoted strings, which don't have to be closed. Other commands don't matter.
[Answer]
# [Haskell](https://www.haskell.org/), 63 bytes
```
main=putStr$take 119"Stack Exchange Chat - The Nineteenth Byte"
```
[Try it online!](https://tio.run/##LcY7CoAwDADQq4TiWrD@HVwUVxe9QCjBlGoRjaCnr4tveoyXp22LWudFWdVNm5rsX9zRhe64ZZYzEfQExrRqFrQexscyhpVgYBTQsDDB5AIJURCG/hVSMX4 "Haskell ‚Äì Try It Online")
The 19th byte is the center `1` in `119`.
[Answer]
# [Wolfram Language (Mathematica)](https://www.wolfram.com/wolframscript/), 60 bytes
```
"Stack Exc"~Print~##&["hange Chat"," - The Nineteenth Byte"]
```
[Try it online!](https://tio.run/##VYyxCsIwEEB3vyJcxakOjg6CqB1cREi30OEIlyZILyE9oSL216Po5PLgweMNKJ4GlGCxuN1S2xySnDndRUsO3Jfrh2Jct2hjM6VM4xgi792//tpTjsm4@rnZvrpSQAvam2omC/N3MlfVyoBH7kkdPQrUoNaq9aQugUmIWLw6PISgewM "Wolfram Language (Mathematica) ‚Äì Try It Online")
The 19th byte is one of the `#`s. `##` represents a sequence of all arguments, but `#` represents only the first argument.
[Answer]
# [APL (Dyalog Classic)](https://www.dyalog.com/), 61 bytes
```
¬Ø12‚åΩ‚àä('ge Chat'{‚ç∫ ‚çµ}' - The Nineteenth Byte'),'Stack Exchan'
```
```
¬Ø12‚åΩ‚àä  ‚çù Rotate right 12
{‚ç∫ ‚çµ}  ‚çù Concatenate
,      ‚çù Concatenate
```
[Try it online!](https://tio.run/##SyzI0U2pTMzJT9dNzkksLs5M/v//0HpDo0c9ex91dGmop6cqOGcklqhXP@rdpfCod2utuoKuQkhGqoJfZl5qSWpqXkmGglNlSaq6po56cElicraCa0VyRmKeOhe1zMFpCvFGAAA "APL (Dyalog Classic) ‚Äì Try It Online")
[Answer]
# [Retina 0.8.2](https://github.com/m-ender/retina/wiki/The-Language/a950ad7d925ec9316e3e2fb2cf5d49fd15d23e3d), 51 bytes
```
Stack Exchange Chat - The Nineteenth Byte
ht.*
hat
```
[Try it online!](https://tio.run/##K0otycxL/P@fK7gkMTlbwbUiOSMxLz1VwTkjsURBVyEkI1XBLzMvtSQ1Na8kQ8GpsiSVK6NET4sLKP3/PwA "Retina 0.8.2 ‚Äì Try It Online") Explanation: Tries to insert the whole string, but if the 19th byte (the `a`) is deleted, then replaces everything after the `C` with `hat`.
[Answer]
# [Pxem](https://esolangs.org/wiki/Pxem), filename: 2 bytes + content: 64 bytes = 66 bytes.
Thank you for commenting me that I need to use content of the file.
## Filename
```
.e
```
## Content
```
Stack Exchange Cha.p.c.c.zt - The Nineteenth Byte.p.d.a.v.st.v.p
```
## How it works
* Every command substring consists of a dot and a char.
* Every non-command substring is considered to be a command to push each of the string from backwards.
	+ I.e. literals.
* Filename is main routine; content is subroutine.
* `.e` calls subroutine.
* 19th byte on content is `.` of `.p` --- a command to pop each to putchar().
	+ Then the stack would be empty.
* `.c` is dup() iff not empty; nop() otherwise.
* `.z ... .a` is `while size<2 || pop!=pop; do ... ;done`.
* `.d` is exit() on filename; `return` on content.
* `.v` reverses entire stack.
## Links to TIO
* [Try it online!](https://tio.run/##nRhrV@JG9Ht/xTAFMgOEAOKuyzhaRXdLq6xVu90VqCdCkGhIAgkKAvvXt/dOEgTXnj6Ox2Ry5859v4aeGQy@/UgGYegHNcO4tcPB5KbY9YbGh5/1S9@03puPT5Zr@FNrWPS9wJ7awdC4cbwbY2jaEdwuVopD211t/xBYIdGtiZgMzeCelEqVirCmvjcOyUn9@uDkRNYFC2e@RW6tsOu5/WxWfQHXoen2@J7Rsx4Md@I4pLKXLWez8eGzg8ufJU2zGI/ofkJAbfH0HF/52jJa6EuasP292fh8fXF5JCul0lYCPPt40fh88uW6/vH8/Lh@KcuiRXSX0PT88ODi5@tPx@cXjY/NGpAhnWx2TpRWHlFaCvzIH4rl6szVa0es4cQxQ4sEAzzg@SGsHr1xL/AdOxSmY5sB0W@Jlp6X8zT9E11qUsO3Jpq/n5zUT49kTbEApZFhTwQDux8q5j2CiDHA6g48kv6RUyJJGVkzBQkGFtgw9DziOb29LHrBDkmZC@vBdAhNkb7pBBZdLF5BJ@v4SgKFM10EVo9ogTE1ZoYI4PFkaIrvE@ksFqCyogQ437EFTcACzoN8906AC33bsRhnfVkSXTOwgEOZEtslrJ/jpA/eEFZgdoUZBNbwxpmh4z3w@YFL9IdwUl6EY6LXA1IqV7aq22/e7rwjWqvt5jra4nZs@aS4MB/viXZ4/KHRnDvApCerbwRYl/lj2w37RPPPvI9u025cd@vBxcOn/nvreHz@@Mf08@zL05V5EF4OT3tHeT2VzmS0xf9gnS5JWm9Rki4R2pFtSsEkjvdojVkQicBopksL6RLnhLapoAIMqanQYJQWLgq0RrlA0fsykJSKvjdmAiLesV2L9PdKgs/tPksAwa4scYUHwAAtWc9m@1L2@PyYcaFYknor6IilBV4niKV2HwfoiWh9wvoc2YmXhKMdJKScWRLL5YrN9wwUh@jICQs4ABBj2Z@43dD2XHLCukr2bgrk5UFodu9bTj7fkd01JDiCOA6fxx6jTmwDB3R3dJ0ncPiLaejlTiwI2GG51JQn9AfiQfio4KNJSERaxzrugYJuXhqtx@nsqWPohmmgBdzdUsycFk1yWCXFCIEuaNeEiIbYpqvgVnjgaxZRMTvGPiU/gWhuHsjVQE8k6SmdjJ6RzaZcHtsygvD5RLp6WUSSuXuTdfcqH8SiREKQR8MjRfNVWV7qEglHzVgewFDuc/8DycTtEKMitnsmaLex9iUpShesRSIzE90JSQUrEVBaJF4wZQlfEKTpPsXVAABakAOT@Z7bDR7GYcfIMXO3zPNGKw@Zp0ffFQ7@saahWBq@MQcyIoACsQx2ywL@460BrAageGjkUilTLOeBTBmtvhV7Q5hoFPu6Y@QNB6g23@vAhpngexCgC4ZqeW4AAgBwgEBjaOiwXYZVIotYliFJX6i5taGmNj9r2flSR6bBr/m88CV86xVICv8rBHA2C8znEUj6UehOboJwzNKlwhYXPcuxoGGctXTd7ohIMTj4p0Naf5JOHs93jTkcYVQB0rRAsyRLCxHJfySQRgqBMbd1WXmB@zcnnfiE4klWTP81x2fBEytC6IPH0xlcASIjpQUpRWg8TfncQ9tB9fTFVKab7wWZyXTkLrEmxLooPkd8DxNpuitnfH4tp3B4JmbyWiw3rA2Ry4x23tif5mc1cPr@VId3Ct45eGfgnZnVoLm9rtdx82iOJegOQvBu1xZ3@XxUhQDtroPZkfRHSLViLm0YWgQwwBxgQ8PApomS54wzluXCuIVvAoOXuIH@qPLAvoZM6FvjcNgBuxtZqJyGCEWS0ACKKgRs8LnaMRG4VMseLrHLYcvur@YB1ZU1zGFW4tpiEX33gPTYCidjFztPxCWPBMxeL@Gq43dwEybfKfyGsSb5bqcR0LMfEkBGIXgJgcAo5ow/Lt8zmoUKCOZ4IdmqHUdl@aJ1LyF5IMGTPjiI@qAGU0KYVB4NDb1YHV21DIsd8vk9ZB2Q6Uh4YD9Afx0CxcNdhIpDcBksCocxAixeEEfRgQFXfb5HoMhxAakddMe2H8pYUOx@ltX7SovQwMYwjqrP9SZ3xo446lP4lfGOPFIygWibDS4yf@rXjfb4y2qDwMZeeW3r1@ctpc3zzuXGDjJF5Z/3P7NzPj@XgKYk0fXY9eR8DWnC6nFPYHp5FwaI@m5l@w3fr9ewn67QPiAtsMDE/WoUDSQ7ccXExeHjmWi8WrXY/XSppq/r8jsyg1P1NdgBO02a0sENTOk1SNnT1/rR6oTPkhEmBQblE/YZnmv7XjRGvL7pskZhVDgqOM8485EEJJi7HMu9DQdsxFUENaDhNHalIxoQPxPGjmRct0eFRqHM@VfaKunvOnT/KF/dqVW3cehZsbFBhjP2YZP3NTst1AtXhS98fipp8bpGml6I9cm6tcZU1CXgiytgq2aeaNirvo2csr3Db8aWeY8Vrw61ttra2u5g7byS1apejw9HKNjp2U50rlyF7laXcgs7aoQE96fQdieWWKLtI@z6bnUHEfe233KuwEqGZ@4RA/5FfiGsrgOyQGeKM3aV@7KuY3fN@GfsctMAwdrm540EeAC33BU@cVVrwfQlyPY7qUIanHAHtviEyVtodIR64eiIi7vo@07XO/LTugPGa6xwMYZbnOc6s2wWZMLZ6oDR4rhGYElRDUwAldQ8hxGz4czH50QDclCGACMFJNbkn7LfCqOII@Qyj7HL4jcVWlGAxcDfdkdrB2f/4eDe@sGnlVAsOprIFYu/QgzXLDHAKrlp@WG0fY@D/QBchijr@z30zDpK3CURT9xDUdnwmCpRDay7eahFDFMH5LqLXlE95DxynFRI6NFnZqoNIa9fVPiApPkX@YuNqbFCgRwD1oCiI9puaV9v1BobvlONa4Ni7gVF7GSjuB78EkcLU4aHMdFRbxnHS7pGrqyxl1pFzGjP2R8ZTs0xRpyvc4Vu@C9pZl6lmQGaGUUTW/u3982D02NZtH6of2xeHjcvpXaB1x9yPO0OTPfWIvWBWfSLXfh7ColOLgcWaUINDi3LDQfkcBZasN0rmsWHYhDCw9e@JXeptCJOyYLEd3TSh4drDi2Szf7wPdZjl@hdqMwbu7Fc61SwzAD3v0N7jczKfn3w2ere/nzsf17Km@dqEIQZE2Yz/CFIvydld1woJ6Pbn6qS50ibFXNtnoZBrV3G0YUvKVx@sM1LNWDpXaJ@qZpgpfCGOM0AcPwd8FnMXpXozeoGAo4xAex7xLd7BSu0h1bB7/qTwkPwJHpmaPF1Nav/rGZo2g7R3WolUQeUYMX2fKe9RGXaZUN7vo/plXL1bXVn6011B24ucEMCq6ghNxpqzei@99/tjLe8yE74onhJTAYomiCMZFvD98fzC6lpyQCI9cOGac3GwQNvULzbsjty9ZNJu53xaMGGlG2eZ7ZLUpZjWQNCV78HjOB@OCK07cLQEm93W@lSJ9INR7d4ak@QIBIGRA@@/QU "Dash ‚Äì Try It Online")
* [Without 19th byte](https://tio.run/##nRhrV@JG9Ht/xTAFMgOEAOKuyzhaRXdLq6xVu90VqCdCkGhIAgkKAvvXt/dOEgTXnj6Ox2Ry5859v4aeGQy@/UgGYegHNcO4tcPB5KbY9YbGh5/1S9@03puPT5Zr@FNrWPS9wJ7awdC4cbwbY2jaEdwuVopD211t/xBYIdGtiZgMzeCelEqVirCmvjcOyUn9@uDkRNYFC2e@RW6tsOu5/WxWfQHXoen2@J7Rsx4Md@I4pLKXLWez8eGzg8ufJU2zGI/ofkJAbfH0HF/52jJa6EuasP292fh8fXF5JCul0lYCPPt40fh88uW6/vH8/Lh@KcuiRXSX0PT88ODi5@tPx@cXjY/NGpAhnWx2TpRWHlFaCvzIH4rl6szVa0es4cQxQ4sEAzzg@SGsHr1xL/AdOxSmY5sB0W@Jlp6X8zT9E11qUsO3Jpq/n5zUT49kTbEApZFhTwQDux8q5j2CiDHA6g48kv6RUyJJGVkzBQkGFtgw9DziOb29LHrBDkmZC@vBdAhNkb7pBBZdLF5BJ@v4SgKFM10EVo9ogTE1ZoYI4PFkaIrvE@ksFqCyogQ437EFTcACzoN8906AC33bsRhnfVkSXTOwgEOZEtslrJ/jpA/eEFZgdoUZBNbwxpmh4z3w@YFL9IdwUl6EY6LXA1IqV7aq22/e7rwjWqvt5jra4nZs@aS4MB/viXZ4/KHRnDvApCerbwRYl/lj2w37RPPPvI9u025cd@vBxcOn/nvreHz@@Mf08@zL05V5EF4OT3tHeT2VzmS0xf9gnS5JWm9Rki4R2pFtSsEkjvdojVkQicBopksL6RLnhLapoAIMqanQYJQWLgq0RrlA0fsykJSKvjdmAiLesV2L9PdKgs/tPksAwa4scYUHwAAtWc9m@1L2@PyYcaFYknor6IilBV4niKV2HwfoiWh9wvoc2YmXhKMdJKScWRLL5YrN9wwUh@jICQs4ABBj2Z@43dD2XHLCukr2bgrk5UFodu9bTj7fkd01JDiCOA6fxx6jTmwDB3R3dJ0ncPiLaejlTiwI2GG51JQn9AfiQfio4KNJSERaxzrugYJuXhqtx@nsqWPohmmgBdzdUsycFk1yWCXFCIEuaNeEiIbYpqvgVnjgaxZRMTvGPiU/gWhuHsjVQE8k6SmdjJ6RzaZcHtsygvD5RLp6WUSSuXuTdfcqH8SiREKQR8MjRfNVWV7qEglHzVgewFDuc/8DycTtEKMitnsmaLex9iUpShesRSIzE90JSQUrEVBaJF4wZQlfEKTpPsXVAABakAOT@Z7bDR7GYcfIMXO3zPNGKw@Zp0ffFQ7@saahWBq@MQcyIoACsQx2ywL@460BrAageGjkUilTLOeBTBmtvhV7Q5hoFPu6Y@QNB6g23@vAhpngexCgC4ZqeW4AAgBwgEBjaOiwXYZVIotYliFJX6i5taGmNj9r2flSR6bBr/m88CV86xVICv8rBHA2C8znEUj6UehOboJwzNKlwhYXPcuxoGGctXTd7ohIMTj4p0Naf5JOHs93jTkcYVQB0rRAsyRLCxHJfySQRgqBMbd1WXmB@zcnnfiE4klWTP81x2fBEytC6IPH0xlcASIjpQUpRWg8TfncQ9tB9fTFVKab7wWZyXTkLrEmxLooPkd8DxNpuitnfH4tp3B4JmbyWiw3rA2Ry4x23tif5mc1cPr@VId3Ct45eGfgnZnVoLm9rtdx82iOJegOQvBu1xZ3@XxUhQDtroPZkfRHSLViLm0YWgQwwBxgQ8PApomS54wzluXCuIVvAoOXuIH@qPLAvoZM6FvjcNgBuxtZqJyGCEWS0ACKKgRs8LnaMRG4VMseLrHLYcvur@YB1ZU1zGFW4tpiEX33gPTYCidjFztPxCWPBMxeL@Gq43dwEybfKfyGsSb5bqcR0LMfEkBGIXgJgcAo5ow/Lt8zmoUKCOZ4IdmqHUdl@aJ1LyF5IMGTPjiI@qAGU0KYVB4NDb1YHV21DIsd8vk9ZB2Q6Uh4YD9Afx0CxcNdhIpDcBksCocxAixeEEfRgQFXfb5HoMhxAakddMe2H8pYUOx@ltX7SovQwMYwjqrP9SZ3xo446lP4lfGOPFIygWibDS4yf@rXjfb4y2qDwMZeeW3r1@ctpc3zzuXGDjJF5Z/3P7NzPj@XgKYk0fXY9eR8DWnC6nFPYHp5FwaI@m5l@w3fr9ewn67QPiAtsMDE/WoUDSQ7ccXExeHjmWi8WrXY/XSppq/r8jsyg1P1NdgBO02a0sENTOk1SNnT1/rR6oTPkhEmBQblE/YZnmv7XjRGvL7pskZhVDgqOM8485EEJJi7HMu9DQdsxFUENaDhNHalIxoQPxPGjmRct0eFRqHM@VfaKunvOnT/KF/dqVW3cehZsbFBhjP2YZP3NTst1AtXhS98fipp8bpGml6I9cm6tcZU1CXgiytgq2aeaNirvo2csr3Db8aWeY8Vrw61ttra2u5g7byS1apejw9HKNjp2U50rlyF7laXcgs7aoQE96fQdieWWKLtI@z6bnUHEfe233KuwEqGZ@4RA/5FfiGsrgOyQGeKM3aV@7KuY3fN@GfsctMAwdrm540EeAC33BU@cVVrwfQlyPY7qUIanHAHtviEyVtodIR64eiIi7vo@07XO/LTugPGa6xwMYZbnOc6s2wWZMLZ6oDR4rhGYElRDUwAldQ8hxGz4czH50QDclCGACMFJNbkn7LfCqOII@Qyj7HL4jcVWlGAxcDfdkdrB2f/4eDe@sGnlVAsOprIFYu/QgzXLDHAKrlp@WG0fY@D/QBchijr@z30zDpK3CURT9xDUdnwmCpRDay7eahFDFMH5LqLXlE95DxynFRI6NFnZqoNIa9fVPiApPkX@YuNqbFCgRwD1oCiI9puaV9v1BobvlONa4Ni7gVF7GSjuB78EkcLU4aHMdFRbxnHS7pGrqyxl1pFzGjP2R8ZTs0xRpyvc4Vu@C9pZl6lmQGaGUUTW/u3982D02NZtH6of2xeHjcvpXaB1x9yPO0OTPfWIvWB6Re78PcUEp1cDizShBIcWpYbDsjhLLSKfrFXNIsPxSCEh699S65SaUWbkgWJr@ikDw/XHFokm/3he6zHLtG7UJg3dmOx1qlglQHuf4f2GpmV@frgstW1/fnY/7yTN8/VHAgjJoxm@DuQfk/K7rhQTia3P1Uhz5E2K@baPA1zWruMkwtfUrj7YJeXar7Su0T9UDXBQuENcZgB4Pg74LOYvSrRm9UNBJxiAtj3iG/3ClZoD62C3/UnhYfgSfTM0OLralb/Wc3QtB2iu9VKog4owYrt@U57icq0y4b2fB3TK@Xq2@rO1pvqDlxc4IIEVlEzbjTTmtF177/bGS95kZ3wRfGOmMxPNEEYybaG74/nF1LTkvkPy4cNw5qNcwdeoHi3ZXfk6heTdjvj0YINGds8z2yXpCzHsgaErn4OGMH1cERo24WZJd7uttKlTqQbTm7x0J4gQSQMiB58@ws)
[Answer]
# [Python 2](https://docs.python.org/2/), 65 bytes
```
a="Exchange Chat"
"#";a+=" - The Nineteenth Byte"
print"Stack",a
```
The nineteenth byte is the quotation mark before the hashtag. Removing it turns line 2 into a comment.
Works in Python 3 for 67 bytes, by adding brackets for the `print()` function.
[Answer]
# [Rust](https://www.rust-lang.org/), 63 bytes
```
||print!("Stac{:.105}","k Exchange Chat - The Nineteenth Byte")
```
The nineteenth byte is the `0` in the formatting parameter.
Removing it changes the format string in the closure to print 15 characters from the argument instead of up to 105.
With the 19th byte: [Try it online!](https://tio.run/##KyotLvmflqeQm5iZp6GpUK2g8b@mpqAoM69EUUMpuCQxudpKz9DAtFZJRylbwbUiOSMxLz1VwTkjsURBVyEkI1XBLzMvtSQ1Na8kQ8GpsiRVSfO/poamNVftfwA "Rust ‚Äì Try It Online")  
Without the 19th byte: [Try it online!](https://tio.run/##BcGxDkAwFAXQ3VdcndoEicHCRqwWfqCRRxvxIjwJwbfXOft5SJgYq/WsDR7o8L7b7llirXqx41NmefGpRC1or9FZngmNs4IUgyN0nkmIWBzqW0iZYLSpoi/8 "Rust ‚Äì Try It Online")
*Thanks to @ErikF for his inspiring [C solution](https://codegolf.stackexchange.com/a/221206/101806)*
]