Radio Shack TRS-80 Model 4 Owner's Manual page 171

String Relations
The relational operators for string expressions are the same as
above, although their meanings are slightly different. Instead of
comparing numerical magnitudes, the operators compare their ASCII
sequence. This allows you to sort string data:
<
Precedes
>
Follows
> <
or
< >
Does not have the same precedence
<
=
Precedes or has the same precedence
>
=
Follows or has the same precedence
BASIC compares the string expressions on a character-by-character
basis. When it finds a non-matching character, it checks to see which
character has the lower ASCII code. The character with the lower
ASCII code is the smaller (precedent) of the two strings.
NOTE: Appendix C contains a listing of ASCII codes for each
character.
Examples of true relational expressions:
"A"
<
"B"
The ASCII code for A is decimal 65; for Bit's 66.
"CODE"
<
"COOL"
The ASCII code for
a
is 79; for D it's 68.
If while making the comparison, BASIC reaches the end of one string
before finding non-matching characters, the shorter string is the
precedent. For example:
"TRAIL"
<
"TRAILER"
Leading and trailing blanks are significant. For example:
"A"
<
"A"
ASCII for the space character is 32; for A, it's 65.
"Z-80"
<
"Z-80A"
The string on the left is four characters long; the string on the right is
five.
How to Use Relational Expressions
Normally, relational expressions are used as the test in an IFITHEN
statement. For example:
IF A
=
1 THEN PRINT "CORRECT"
BASIC tests to see if A is equal to 1. If it is, BASIC prints the
message.
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