Friday, August 22, 2014

Arpanet a binary trip.


How do we translate the sign? Light on is a one and light off is a zero.



There is an old joke that says: "There are only 10 types of people in the world: those who understand binary and those who do not." In any case, it does not hurt to at least look at binary once in a while. Ascii (American standard code for information interchange) is usually eight binary characters of ones or zeroes. So you can take the first 8 ones and zeros for the first character.


Then to further split out the whole code sequence:


 01000001 01010010 01010000 01000001 01001110 01000101 01010100

Then you can convert on character at a time.  You can just look at a table or write a program to do it.


Datafile af:
 01000001 01010010 01010000 01000001 01001110 01000101 01010100

$ ./b2a1.sh af
ARPANET


[code]
 #!/bin/bash

chrbin() {
        echo $(printf \\$(echo "ibase=2; obase=8; $1" | bc))
}

ordbin() {
  a=$(printf '%d' "'$1")
  echo "obase=2; $a" | bc
}

ascii2bin() {
    echo -n $* | while IFS= read -r -n1 char
    do
        ordbin $char | tr -d '\n'
        echo -n " "
    done
}

bin2ascii() {
    for bin in $*
    do
        chrbin $bin | tr -d '\n'
    done
}
while read z
do
bin2ascii $z
done < $1
echo
[/code]

[code]

<html>
<head>

<script type="text/javascript">
var input_id = "bin_text";
var answer_id = "answer";

function convertToASCII() {
 var bin_text = document.getElementById(input_id);
 var answer = document.getElementById(answer_id);

 if (!answer) {
  alert("Error: No element with id \""+answer_id+"\".");
  return;
 }
 if (bin_text)
  var text = bin_text.value;
 else {
  error("No element with id \""+input_id+"\".");
  return;
 }
 var divisible = text.length % 8;
 var nonBinary = /[^0|1]/.test(text);
 if (text.length > 0 && divisible == 0 && !nonBinary) {
  var regex = /[0|1]{8}/g;
  var str = text.match(regex);
  var code = 0;
  var placeVal, exp, digit;
  var ascii = '';
  while (str.length > 0) {
   code = 0;
   for (var i=0; i<str[0].length; i++) {
    placeVal = 7-i;
    exp = Math.pow(2, i);
    digit = str[0].charAt(placeVal);
    code += exp*digit;
   }
   str.shift();
   ascii += String.fromCharCode(code);
  }
  answer.innerHTML = "<p class=\"binary\">" + ascii + "</p>";
 }
 else {
  error("Malformed binary.");
  return;
 }

 function error(errText) {
  answer.innerHTML = "<span class=\"error\">Error: " + errText + "</span>";
 }
}
</script>

<style type="text/css">
.block {
 width: 45%;
 border: 1px solid #000000;
 padding: 10px;
}
.binary {
 background-color: #C6FFC7;
 padding: 3px;
}
.error {
 background-color: #FFC6C6;
 padding: 3px;
}
</style>

</head>
<body>

<div style="float:left;" class="block">
 <form onSubmit="convertToASCII(); return false;">
  <p>Enter some binary to decode:</p>

  <input type="text" id="bin_text"/>
 </form>
</div>

<div style="float:right;" class="block">
 <p id="answer"><br/></p>
</div>

</body>
</html>

[/code]

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