ruby, 46 bytes

Result

AC

Duration

1485ms

Code [DL]

puts $<.chars.map{|c|c<'['?'1':'0'}.join.chop!

stdin

abcDefghIjklmNOpqRstuvwxyz

stdout

00010000100001100100000000

stderr

/volume/CODE:1: warning: ARGF#chars is deprecated; use #each_char instead

strace

10    execve("/bin/sh", ["/bin/sh", "/root/script", "/volume/CODE"], 0x7ffcf1d1e470 /* 9 vars */) = 0
11    execve("/bin/cat", ["cat", "-"], 0x555fbb3fed40 /* 9 vars */) = 0
12    execve("/usr/local/ruby-2.7.1/bin/ruby", ["/usr/local/ruby-2.7.1/bin/ruby", "/volume/CODE"], 0x555fbb3fed60 /* 9 vars */ <unfinished ...>
11    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
12    <... execve resumed>)             = 0
12    +++ exited with 0 +++
10    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=12, si_uid=0, si_status=0, si_utime=5, si_stime=5} ---
10    +++ exited with 0 +++