cat command prints the contents of a file to the terminal (console).
  $  cat «FILENAME»
When used in this manner, it is primarily useful for human-readable files (i.e., text
files).

xxd command shows you the individual bytes in a file, in hex (default) or binary bits (if
selected) format.  Use it to troubleshoot.

To view the bytes in hex format:  (don't type the '$')
  $  xxd -g1 «FILENAME»

To view the bytes in binary format:  (don't type the '$')
  $  xxd -g1 -b «FILENAME»

To view the options for xxd:
  $  xxd --help

To view the full man page (documentation) for xxd:
  $  man xxd

xxd is the best choice for "binary files" (not meant for human reading).  Binary files may
contain bytes with value ≥127 and/or <32.

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REMEMBERING VALUES

Dec  Hex  Binary
  0    0         0   easy
  1    1         1   easy
  2    2        10   power of 2
  3    3        11
  4    4       100   power of 2
  5    5       101   (picture?)
  6    6       110
  7    7       111   one less than a power of 2 are all 1s
  8    8      1000   power of 2
  9    9      1001
 10    a      1010   "ten ten"
 11    b      1011   "│₀\\"  -OR_  "ten eleven"
 12    c      1100   (picture)
 13    d      1101   (picture)
 14    e      1110   (picture)
 15    f      1111   one less than a power of 2 ⇒ all 1s

"C"
/⁰ » /\⁰₀ » 1100
\₀


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HEX IN CONSTANTS / LITERALS

character constant (character literal)
'C'
'\x43'
// '\x▒▒' for character literal using hex notation

string literal
"C"
"\x43"
// "\x▒▒" for string literal using hex notation

integer constant (integer literal)
67
0x43
// 0x▒▒ for integer literal using hex notation

__________________________________________________
HOW TO CREATE TEST INPUT FILES FOR TESTING

Create a text file containing exactly three bytes.
$  echo -e -n '\xdb\xacC' > dbacC.txt

-e means to interpret C-style escapes.
-n means to NOT add a newline at the end.

Better yet, use the method illustrated today.