Editing BASIC (section)

==== Unstructured BASIC ====
New BASIC programmers on a home computer might start with a simple program, perhaps using the language's PRINT statement to display a message on the screen; a well-known and often-replicated example is [[The C Programming Language|Kernighan and Ritchie]]'s [["Hello, World!" program]]:

<syntaxhighlight lang="basic">
10 PRINT "Hello, World!"
20 END
</syntaxhighlight>

An [[infinite loop]] could be used to fill the display with the message:

<syntaxhighlight lang="basic">
10 PRINT "Hello, World!"
20 GOTO 10
</syntaxhighlight>

Note that the <code>END</code> statement is optional and has no action in most dialects of BASIC. It was not always included, as is the case in this example. This same program can be modified to print a fixed number of messages using the common <code>FOR...NEXT</code> statement:

<syntaxhighlight lang="basic">
10 LET N=10
20 FOR I=1 TO N
30 PRINT "Hello, World!"
40 NEXT I
</syntaxhighlight>

Most home computers BASIC versions, such as [[MSX BASIC]] and [[GW-BASIC]], supported simple data types, loop cycles, and arrays. The following example is written for GW-BASIC, but will work in most versions of BASIC with minimal changes:

<syntaxhighlight lang="basic">
10 INPUT "What is your name: "; U$
20 PRINT "Hello "; U$
30 INPUT "How many stars do you want: "; N
40 S$ = ""
50 FOR I = 1 TO N
60 S$ = S$ + "*"
70 NEXT I
80 PRINT S$
90 INPUT "Do you want more stars? "; A$
100 IF LEN(A$) = 0 THEN GOTO 90
110 A$ = LEFT$(A$, 1)
120 IF A$ = "Y" OR A$ = "y" THEN GOTO 30
130 PRINT "Goodbye "; U$
140 END
</syntaxhighlight>
The resulting dialog might resemble:

 What is your name: Mike
 Hello Mike
 How many stars do you want: 7
 *******
 Do you want more stars? yes
 How many stars do you want: 3
 ***
 Do you want more stars? no
 Goodbye Mike

The original Dartmouth Basic was unusual in having a matrix keyword, MAT.{{efn|From version 3 onwards.}} Although not implemented by most later microprocessor derivatives, it is used in this example from the 1968 manual<ref>{{Cite book|url=http://bitsavers.trailing-edge.com/pdf/dartmouth/BASIC_4th_Edition_Jan68.pdf |archive-url=https://web.archive.org/web/20140103140704/http://bitsavers.trailing-edge.com/pdf/dartmouth/BASIC_4th_Edition_Jan68.pdf |archive-date=2014-01-03 |url-status=live|title=Basic: a manual for BASIC, the elementary algebraic language designed for use with the Dartmouth Time Sharing System|last1=Kemeny|first1=John G.|last2=Kurtz|first2=Thomas E.|date=January 1968|publisher=Dartmouth College Computation Center|location=Hanover, N.H.|language=en|edition=4th|page=53}}</ref> which averages the numbers that are input:

<syntaxhighlight lang="basic">
5 LET S = 0
10 MAT INPUT V 
20 LET N = NUM 
30 IF N = 0 THEN 99 
40 FOR I = 1 TO N 
45 LET S = S + V(I) 
50 NEXT I 
60 PRINT S/N 
70 GO TO 5 
99 END
</syntaxhighlight>