QBASIC的所有语言及其用途，并举例。（追加60）

语法

和Quick BASIC类似而又不同于微软其他BASIC的早期实现版本的是，QBASIC是一种结构化的编程语言。和GW-BASIC相比，QBASIC的主要改进是：

扩充了变量和常量的类型

变量名长度：40个字符

增加了长整型、定卖纯长字符型变量

可定义数值常量、字符串常量

提供了新的选择结构

条件语句

IF <条件> THEN <语句组1> ELSE <语句组2> END IF

多分支语句SELECT

改进了循环结构

增加以下两个循环语句:

WHILE循环

WHILE <条件> <循环中丛咐体> WEND

DO循环

DO WHILE <条件> <循环体> LOOP

子程序郑升和函数作为单独的模块

不需要行号

代码示例（赋值,求和运算,并显示结果）

let A=10

let B=20

let C=A+B

Print C

快捷键

Ctrl+Break：中断正在运行的程序；

F5：继续运行被中断的程序；

Shift+F5：从第一条语句开始重新运行程序；

F4：当程序中断运行时，查看运行结果屏幕，再按一次F4则切换回代码屏幕；

F1：获得帮助

课件和视频可能找不到，对不起

QBASIC - Statements

命令：

BEEP, BLOAD, BSAVE, CALL, CHAIN, CHDIR, CIRCLE, CLEAR, CLOSE, CLS, COLOR, COM, COMMON, CONST, DATA, DATE$, DECLARE, DEF, DEFDBL, DEFINT, DEFLNG, DEFSNG, DEFSTR, DIM, DO, DRAW, END, ENVIRON, ERASE, ERROR, EXIT, FIELD, FILES, FOR, FUNCTION, GET, GOSUB, GOTO, IF, INPUT, IOCTL, KEY, KILL, LET, LINE, LINE INPUT, LOCATE, LOCK, LPRINT, LSET, MID$, MKDIR, NAME, ON, OPEN, OPTION, OUT, PAINT, PALETTE, PCOPY, PEN, PLAY, POKE, PRESET, PRINT, PSET, PUT, RANDOMIZE, READ, REDIM, REM, RESET, RESTORE, RESUME, RETURN, RMDIR, RSET, RUN, SCREEN, SEEK, SELECT CASE, SHARED, SHELL, SLEEP, SOUND, STATIC, STOP, STRIG, SUB, SWAP, SYSTEM, TIME$, TROFF, TRON, TYPE, UNLOCK, VIEW, WAIT, WHILE, WIDTH, WINDOW, WRITE

程序：

CALL

CHAIN

DECLARE

END

OPTION

REM

RUN

STOP

事件：

ON

SLEEP

WAIT

结构：

DO

ERROR

EXIT

FOR

FUNCTION

GOSUB

GOTO

IF

RESUME

RETURN

SELECT CASE

SUB

WHILE

数据

CLEAR

COMMON

CONST

DATA

DEFDBL

DEFINT

DEFLNG

DEFSNG

DEFSTR

DIM

ERASE

INPUT

LET

MID$

RANDOMIZE

READ

REDIM

RESTORE

SHARED

SWAP

STATIC

TYPE

Pen

PEN

Joystick

STRIG

Keyboard

INPUT

KEY

LINE INPUT

Screen

CLS

COLOR

LOCATE

PALETTE

PCOPY

PRINT

SCREEN

VIEW

WIDTH

WINDOW

Printer

LPRINT

WIDTH

Graphics

CIRCLE

DRAW

GET

LINE

PAINT

PRESET

PSET

PUT

Sound

BEEP

PLAY

SOUND

Memory

BLOAD

BSAVE

CLEAR

DEF

DEF SEG

POKE

File

CLOSE

KILL

NAME

OPEN

RESET

Sequential file

INPUT

LINE INPUT

PRINT

WRITE

Random file

FIELD

GET

LOCK

LSET

PUT

RSET

SEEK

UNLOCK

Binary file

BLOAD

BSAVE

Directory

CHDIR

MKDIR

RMDIR

System

COM

ENVIRON

IOCTL

OUT

SHELL

SYSTEM

Date &Time

DATE$

TIME$

Debug

TROFF

TRON

BEEP

Sounds the speaker at 800 Hz for 1/4 second.

PRINT CHR$(7) also beeps

CIRCLE

>SCREEN 1: CIRCLE

CLOSE

Close an open file

>OPEN

DATA

>maskinkode: array

DEF

DEF SEG

Sets the current segment address.

DEF SEG [=address]

address A segment address used by BLOAD, BSAVE, CALL ABSOLUTE, PEEK, or POKE

- a value in the range 0 - 65535.

If address is omitted, DEF SEG resets the current segment address to the default data segment.

Example:

DEF SEG = 0

Status% = PEEK(&H417)

POKE &H417, (Status% XOR &H40)

DEF SEG

Read keyboard status.

Change Caps Lock state, bit 6.

Reset segment address.

>maskinkode: array

DIM

DIM declares an array or specifies a data type for a nonarray variable.

>REDIM, $DYNAMIC, $STATIC

DIM [SHARED] variable[(subscripts)] [AS type][, variable[(subscripts)] [AS type]]...

SHARED Specifies that variables are shared with all SUB or FUNCTION procedures in the module.

subscripts Dimensions of the array, expressed as follows:

[lower TO] upper [, [lower TO] upper]...

lower The lower bound of the array's subscripts.

The default lower bound is zero.

upper The upper bound.

>OPTION BASE

AS type Declares the data type of the array or variable:

INTEGER A 16-bit signed integer variable

LONG A 32-bit signed integer variable

SINGLE A single-precision 32-bit floating-point variable

DOUBLE A double-precision 64-bit floating-point variable

STRING * n% A fixed-length string variable n% bytes long

STRING A variable-length string variable

DIM i%

DIM i AS INTEGER

DIM s AS STRING * 20

DIM a(4) AS SINGLE'5 numbers (0 to 4)

DRAW

>SCREEN 1: DRAW

GET

>GET [File I/O]

>GET [Graphics]

IF...THEN...ELSE

IF condition THEN statements [ELSE statements]

IF condition THEN

statements

[ELSEIF condition THEN

statements]...

[ELSE

statements]

END IF

KEY

>KEY [Assignment]

>KEY [Event Trapping]

LINE (Graphics)

>SCREEN 1: LINE

LOCATE

>SCREEN 0: LOCATE (show/hide/define cursor)

LPRINT

>Printer: LPRINT

>PRINT

MID$

The MID$ statement replaces part of a string variable with another string.

MID$(stringvariable$,start%[,length%])=stringexpression$

stringvariable$ The string variable being modified.

start% The position of the first character in the substring being replaced.

length% The number of characters in the substring. If the length is omitted, MID$ replaces all characters to the right of the start position.

stringexpression$ The replacement string. It can be any string expression.

Ex:

Text$ = "Paris, France"

PRINT Text$

MID$(Text$, 8) = "Texas "

PRINT Text$

Paris, France

Paris, Texas

>Function: MID$()

PAINT

>SCREEN 1: PAINT

PALETTE

>SCREEN 1: PALETTE

PLAY

>Sound: PLAY

>SOUND

>PLAY (Event Trapping)

POKE

>DEF SEG

>SCREEN 0: POKE (attributes and chars)

>PEEK()

PRESET

>PSET

>SCREEN 1: PRESET

PSET

>PRESET

>SCREEN 1: PSET

PUT

>PUT (File I/O)

>PUT (Graphics)

>GET

RANDOMIZE [seed]

Benytter 'seed' til at danne en ny start p? den sekvens af 'tilf?ldige' tal, som RND() returnerer.

Med en fast seed-v?rdi kan man sikre, at den tilf?ldige sekvens altid er den samme:

RANDOMIZE 124

FOR i = 1 TO 4

PRINT RND

NEXT

.2441675

.214439

.6458486

.7624476

Hvis talsekvensen skal v?re 'rigtig tilf?ldig' benyttes

RANDOMIZE TIMER

der benytter maskines aktuelle tid som seed.

REDIM

REDIM declares or resizes a dynamic array, erasing any previous values.

REDIM [SHARED] variable[(subscripts)] [AS type][, variable[(subscripts)] [AS type]]...

>DIM

SOUND

>Sound: SOUND

>PLAY

SYSTEM

Lukker alle ?bne filer og returnere til operativsystemet (DOS)

VIEW

Definerer et omr?de af en grafik-sk?rm ("viewport") - grafik (men ikke tekst) bliver begr?nset til dette omr?de.

VIEW Uden parametre nulstiller en defineret Viewport - s? hele sk?rmen benyttes til grafik.

Grafikkoordinater er relative til en defineret Viewport - men:

VIEW SCREEN ... benytter absolutte koordinater.

CLS rydder kun det indre af en Viewport.

VIEW [[SCREEN] (x1!,y1!)-(x2!,y2!) [,[color%] [,border%]]]

SCREEN Specifies that coordinates are relative to the

screen rather than the viewport.

(x1!,y1!)-(x2!,y2!)The coordinates of diagonally opposite corners

of the viewport.

color% A color attribute that sets the viewport fill

color. Depends on Screen mode.

border%A color attribute that sets the viewport border

color. Depends on Screen mode.

F?lgende to rutiner (uden og med SCREEN) giver samme resultat (bem?rk parametrene til CIRCLE):

SCREEN 1

VIEW (80, 80)-(160, 120), , 1

LOCATE 13, 13: PRINT "A viewport"

CIRCLE (25, 20), 30

SCREEN 1

VIEW SCREEN (80, 80)-(160, 120), , 1

LOCATE 13, 13: PRINT "A viewport"

CIRCLE (105, 100), 30

et udsnit af sk?rmen:

view1.gif (1722 bytes)

SCREEN 1

VIEW (80, 80)-(160, 120), 2, 1

LOCATE 13, 13: PRINT "A viewport"

CIRCLE (25, 20), 30

view2.gif (1904 bytes)

WHILE...WEND

WHILE

'statements

WEND

Wait for any key:

WHILE Inkey$="": WEND

WIDTH

>SCREEN

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