查看“︁BASIC”︁的源代码

BASIC 有三代

* Dartmouth
* Structed
* Object-oriented

= 解释器 =

Dartmouth: [https://github.com/nigelperks/LegacyBasic Legacy Basic]

= 编译器 =

Dartmouth: [https://github.com/cpp-tutor/dbasic dbasic]

使用

<pre>dbasic 1 &lt; hello.bas &gt; hello.ll
clang -O3 -o hello hello.ll  runtime/basic_lib.c -lm
./hello</pre>

= 基础 =

开头一般写行号×10,因为可以补救

* <code>REM</code> 注释
* <code>PRINT</code> 输出： <code>&quot;&quot;</code> 里包含字符串 <code>,</code> 或者 <code>;</code> 负责分割数值和字符串
* <code>END</code> 结束

<span id="解释器-1"></span>
== 解释器 ==

前面不加行号

* <code>RUN</code> 解释器运行
* <code>STOP</code> 解释器停止运行
* <code>LIST</code> 显示代码，后面可以跟行号

= 赋值 =

== 单个 ==

* <code>LET</code> 赋值 声明变量

== 多个 ==

* <code>READ</code> 批量未赋值声明
* <code>DATA</code> 批量赋值，多出来的不处理，这里的 8 9 10

<pre>410 READ A1, A2, A3
420 READ B1, B2, B3, B4
430 DATA 1, 2, 3, 4, 5
440 DATA 6, 7, 8, 9, 10
450 PRINT A1, A2, A3,
460 PRINT B1, B2, B3, B4</pre>
= 流程控制 =

<span id="if"></span>
== IF ==

* <code>IF</code> 行号

<pre>310 IF S &lt; 0 THEN 350</pre>
<span id="goto"></span>
== GOTO ==

* <code>GOTO</code> 行号

<span id="for-next"></span>
== FOR &amp; NEXT ==

* <code>FOR</code> 循环范围，步数
* <code>NEXT</code> 结束循环

<pre>250 LET S = 0
260 FOR N = 1 TO 3 STEP 2
270 LET S = S + N
280 NEXT N</pre>
<span id="gosub-return"></span>
== GOSUB &amp; RETURN ==

* <code>GOSUB</code> 去
* <code>RETURN</code> 回到 GOSUB 位置

<pre>10 LET X = 2
20 IF X&lt;0 THEN 60
30 X = X - 1
40 PRINT &quot;X (BEFORE) IS &quot;, X
50 GOSUB 20
60 PRINT &quot;X (AFTER) IS &quot;, X
70 IF X&lt;0 THEN 90
80 RETURN
90 PRINT &quot;END&quot;
100 END</pre>
= 计算 =

== 函数 ==

* <code>SIN()</code> P/6=30度 P/3=60度 P/2=90度
* <code>COS()</code>
* <code>TAN()</code>
* <code>ATN()</code> tan 的倒数
* <code>EXP()</code> e^<code>()</code>
* <code>LOG()</code>
* <code>SQR()</code> 平方根
* <code>ABS()</code> 绝对值
* <code>RND</code>随机数 ## 表达式
* <code>&gt;</code>
* <code>&lt;</code>
* <code>=</code>
* <code>&lt;&gt;</code> 不等于
* <code>&gt;=</code>
* <code>&lt;=</code>

= 矩阵 =

<code>DIM</code> 数组/矩阵

<pre>10 DIM A(10) 
20 FOR I = 0 TO 10
30 A(I) = I * 2  
40 NEXT I
50 FOR I = 0 TO 10
60 PRINT &quot;A(&quot;; I; &quot;) = &quot;; A(I)
70 NEXT I
80 END</pre>

= 示例 =

<pre>10 REM INTRO TO BASIC PROGRAMMING: REM &amp; PRINT
20 PRINT &quot;HELLO, THIS IS BASED ON FIRST BASIC INSTUCTION MANUAL (1964)&quot;
30 REM INTERGRES AND FLOAT: LET &amp; EXPO &amp; LOG &amp; SQR &amp; ABS
40 LET X=2
50 PRINT &quot;X IS &quot;, X
60 LET Y=(7+8)/3
70 PRINT &quot;Y=(7+8)/3 IS &quot;, Y
80 LET Z=2/3
90 PRINT &quot;Z=2/3 IS &quot;, Z
100 LET A = Y ^ X * 5
110 PRINT &quot;A=Y^X IS &quot;, A
120 LET B = 2* ( (P/6) + COS(P/3) )
130 PRINT &quot;2(SIN30+COS60) IS &quot;, B
140 LET C = EXP(0)
150 PRINT &quot;EXPO(0) IS &quot;, C, &quot; WHICH MEANS E^0&quot;
160 LET D = LOG(1)
170 PRINT &quot;LOG(0) IS &quot;, D
180 LET E = SQR(4)
190 PRINT &quot;SQR(4) IS &quot;, E
200 LET F = ABS(-12)
210 PRINT &quot;ABS(-12) IS &quot;, F
220 PRINT &quot;THE CALCULATION RESULTS AVOBE ARE &quot;, A, B, C, D, E, F
230 REM  FOR: FOR &amp; NEXT
240 PRINT &quot;FOR IS STARTING NOW&quot;
250 LET S = 0
260 FOR N = 1 TO 3 STEP 2
270 LET S = S + N
280 NEXT N
290 PRINT S
300 REM GOTO, IF THEN. = &gt; &lt; (&lt;&gt; not equal) ALL ARE ALLOWED: GOO &amp; IF &amp; THEN
310 IF S &lt; 0 THEN 350
320 LET S = S - 1
330 PRINT &quot;NOW S IS &quot;, S
340 GOTO 310
350 PRINT &quot;IF IS END. S is &quot;; S 
360 REM DEF: DEF
370 DEF FNC(G) = G^3 + 2.7*G
380 LET H = FNC(Y)
390 PRINT H
400 REM READ, DATA. LET BY BATCH: READ &amp; DATA
410 READ A1, A2, A3
420 READ B1, B2, B3, B4
430 DATA 1, 2, 3, 4, 5
440 DATA 6, 7, 8, 9, 10
450 PRINT A1, A2, A3,
460 PRINT B1, B2, B3, B4
470 END</pre>


[[分类:Software]]