Pascal Tutorial 1B - Identifiers

1B - Identifiers

Identifiers are names that allow you to reference stored values, such as variables and constants. Also, every program must be identified (get it?) by an identifier.

Rules for identifiers:

Must begin with a letter from the English alphabet.
Can be followed by alphanumeric characters (alphabetic characters and numerals), or the underscore (_).
May not contain special characters, such as:
~ ! @ # $ % ^ & * ( ) _ + ` - = { } [ ] : " ; ' < > ? , . / | \

Several identifiers are reserved in Pascal -- you cannot use them as your own identifiers. They are:

and	array	begin	case	const	div	do	downto
else	end	file	for	forward	function	goto	if
in	label	mod	nil	not	of	or	packed
procedure	program	record	repeat	set	then	to	type
until	var	while	with

Also, Pascal has several pre-defined identifiers. You can replace them with your own definitions, but then you'd be deleting part of the functionality of Pascal.

abs	arctan	boolean	char	cos	dispose	eof	eoln
exp	false	input	integer	ln	maxint	new	odd
ord	output	pack	page	pred	read	readln	real
reset	rewrite	round	sin	sqr	sqrt	succ	text
true	trunc	write	writeln

Pascal is not case sensitive! MyProgram, MYPROGRAM, and mYpRoGrAm are equivalent. But for readability purposes, it is a good idea to use meaningful capitalization!

Identifiers can be any length, but many Pascal compilers will only look at the first 32 characters or so. That is,
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFAlphaBeta ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGammaDelta
may be equivalent to some Pascal compilers because the differences begin in the 33rd character.

To make your code compilable by all compilers, use a reasonable length for identifiers -- up to 15 characters. That way, you'll also save on typing.