Problems of Symbol Congestion in Computer Languages; ASCII Jam vs Unicode

By Xah Lee. Date: . Last updated: .

Symbol Congestion Problem

emacs regex affair 05703
emacs regex affair 05703

Vast majority of computer languages use ASCII as its character set. This means, it jams multitude of operators into about 20 symbols. Often, a symbol has multiple meanings depending on context. Also, a sequence of chars are used as a single symbol as a workaround for lack of symbols. Even for languages that use Unicode as its char set (For example, Java, XML), often still use the ~20 ASCII symbols for all its operators. The only exceptions i know of are Mathematica, Fortress, APL. This page gives example and problems of symbol congestion.

Symbol Congestion Examples

Multiple Meanings of a Symbol

Here are some common examples of a symbol that has multiple meanings depending on context:

In Java, the SQUARE BRACKET [ ] is used for declaring array type main(String[] args). Also, part of syntax for array initiation xArray = new int[10];. Also, a delimiter for getting a element of array xArray[i].

In Java and most other languages, PARENTHESIS ( ) is used for expression grouping (x + y) * z, also as delimiter for arguments of a function call System.out.print(x), also as delimiters for parameters of a function's declaration main(String[] args).

In C, Perl, JavaScript , and others, COLON : is used as a separator in a ternary expression (For example, (test ? "yes" : "no")), also as a namespace separator (For example, use Data::Dumper;).

In URL, SOLIDUS / is used as path separator, also as indicator of protocol. For example,

In Python and many others, LESS-THAN SIGN “<” is used for “less than” boolean operator, but also as a alignment flag in its “format” method, also as a delimiter of named group in regex, and also as part of char in other operators that are made of 2 chars, example: {<<, <=, <<=, <>}.

The above are just some examples to illustrate the issue. There are perhaps 100 times more.

Examples of Multi-Char Operators

Here are some examples of common operators that are made of multiple characters:

Problems of Symbol Congestion

The tradition of sticking to the 95 chars in ASCII of 1960s is extremely limiting. It creates complex problems manifested in the following.

String Escape Mechanism

String Escape mechanism, for example, C's backslash {\n, \r, \t, \/, etc}, widely adopted. A better solution would be Unicode symbols for unprintable chars. Example candidates:

(Note: string escape mechanism is ultimately necessary, but using proper Unicode can alleviate 99% of the need. [see ASCII Characters])

Crazy Leaning Toothpicks Syndrome

The backslash string escape mechanism directly leads to crazy leaning toothpicks syndrome, especially bad in emacs regex. [see Emacs regex tutorial]

Here is a example of a good design, when Unicode characters are used as meta-characters:

“<img src="〔「^"」+〕" alt="〔「^"」+〕" width="〔「0-9」+〕" height="〔「0-9」+〕">”

Confusing Context Sensitive Symbols

This is particularly bad in regex. For example, ^ has multiple meanings depending on where it is placed. If in the beginning, it's a line beginning marker, if as first char inside square brackets, for example: [^…] then it's a negation, otherwise it's literal.

Many other regex chars also have special meaning, some depends on their position. For example, ^ $ ? | . + \ - { } ( ) [ ] ….

Whether a symbol's meaning is literal, or whether their position changes meaning, or wether meaning is changed inside [], is completely ad hoc.

Complex Delimiters for Strings

The lack of bracketing symbols leads to varieties of unnecessarily complex string delimiters to help solve the problem of quoting.

Python's triple quotes: {'''…''', """…"""}. [see Python: Quote String]

Perl's varying delimiters: {q(…), q[…], q{…}, m/…/}. [see Perl: Quote Strings]

Perl, PHP, unix shell's “heredoc”. [see PHP: String Syntax]

[see Programing Language Design: String Syntax]

HTML Entities

HTML entities, for example, { &amp;, &lt;, &gt;, &quot;, &alpha;, &#945;, &#x3b1;, etc}. [see HTML XML Entities]


<p>4 > 3 is true</p>

is written as:

<p>4 &gt; 3 is true</p>

The HTML entities are invented partly as a mechanism of avoiding symbol jam of the characters: < > &, and partly as a kludge for entering frequently needed symbols (For example, © ™ α → …), and partly as a kludge to avoid char encoding and transmission problem (i.e. there is no UNICODE in 1980s, and only ASCII and a handful other basic encoding is widely recognized.).

For a concrete example of how this induced complexity in code, see: ASCII Jam Problem: HTML Entities .

When you are writing a tutorial about HTML in HTML, and trying to tell user how to represent the ampersand character, you will have things like this: &amp;amp;. And when you have scripts that process HTML, it gets very complex.

Ampersand in URL, URL Percent Encoding

URL percent encoding and encoding Unicode in URL. Example:


The complexity in resolving the ambiguity of the Ampersand char in URL and CGI protocol.

Representation for: Unprintable Character, Their Input Methods, Keyboard Keys

When a language or config needs to represent keystrokes, the ASCII jam made complexities and readibility much worse. See:

For example, in emacs, you will encounter \n \r \t \f and ^J ^M ^I ^L and C-m RET <return> Enter ^m control-m 13 (?\C-m). [see Emacs's Key Syntax Explained]

In Mac OS X's Keybinding system the “DefaultKeyBinding.dict”, you have:

"@b" = ("insertText:", "Cmd+b pressed.");
"~a" = ("insertText:", "Opt+a pressed.");
"^b" = ("insertText:", "Crtl+b pressed.");
"^@a" = ("insertText:", "Ctrl+Cmd+a pressed.");
"^~a" = ("insertText:", "Crtl+Opt+a pressed.");
"#2" = ("insertText:", "2 on the number keypad pressed.");

[see macOS: Create Custom Keyboard Layout]

!n::Run Notepad ; this means Alt+n
^n::Run Notepad ; this means Ctrl+n
+n::Run Notepad ; this means Shift+n
#n::Run Notepad ; this means the Win+n

[see AutoHotkey Key Syntax]

If Unicode is used, some of these problems can be alleviated. . [see Unicode: Keyboard Symbols ⌘ ↵ ⌫]

Fortress and Unicode

All these problems occur because we are jamming so many meanings into about 20 symbols in ASCII.

Problem of Typing Unicode?

Today, it's trivial to create a keyboard layout to type any set of Unicode symbols you choose. See: How to Create a APL or Math Symbols Keyboard Layout .

Some people may find that typing a character not on keyboard directly is an issue, but that is mostly psychological. Note that in Japanese, Chinese, where there are millions of computer users and programers, every character is typed by a input method.

Unicode, Encoding, Escape Sequence, Issues