认识长方形和正方形
长治市城区建东小学
刘 海 云
【教学内容】 五年制小学数学第四册１４６页例１。
【教学目标】
１、 通过观察、测量和动手操作，使学生进一步掌握
长方形、正方形的特征。
２、 培养学生观察、操作、概括、想象的能力，发展
学生的空间观念。
３、 初步渗透“认识来源于实践”的辩证唯物主义观
点。
【教学重点】长方形、正方形的特征。
【教学难点】长方形、正方形的异同点
【教具准备】多媒体课件、实物投影仪、液晶投影仪、
钉子磁力板、长方形、正方形图片、小棒
【学具准备】 长方形、正方形纸片、三角板、１厘米宽的
８根硬纸条或小棒（４根长、４根短）
【教学过程】
一、复习铺垫：
在一年级时， 同学们已初步认识了长方形和正方形，
现在请同学们观察一下在我们的教室里， 哪些东西的面是
长方形，哪些东西的面是正方形？
（生举例后师导入课题：认识长方形和正方形）
二、教学长方形、正方形特征。
１、出示长方形图形
⑴观察长方形的边的特点：有４条边，对边相等。
先观察长方形有几条边？边问、边摸、边数，在学生
摸的过程中根据摸的顺序渗透“对边（邻边）”的概念。
再观察对边的长有什么关系？是怎样知道的？
引导学生自己寻找不同方法（如折一折， 量一量、比
一比等）证明长方形的对边相等。
⑵观察长方形的角的特点：有４个角，都是直角。
引导学生用三角板的直角比一比长方形的４个角。
２、出示正方形图形
⑴现在请同学们用我们观察长方形特点的方法来观察
正方形的边和角有什么特点？ 能用手中的学具证明吗？试
试看。（同桌讨论，动手操作）
⑵告诉我们大家你发现了什么？
重点证明正方形的四条边都相等
３、小结长方形和正方形的相同点和不同点
相同点：都有四条边和四个直角
不同点：长方形的对边相等，正方形的四条边都相等。
三、巩固长方形、正方形的特征
１、填空：
（１） 长方形和正方形都有＿条边，＿个角，都是＿
角。
（２）长方形的＿边相等，正方形的＿＿边都相等。
２、 利用所学的知识判断在这些图形中几号图形是长
方形？ 几号图形是正方形？有什么特点？几号图形是四边
形？（图略）
３、摆一摆
（１）请同学们拿出４根小棒摆出一个长方形。
（２）摆出一个正方形。
４、拉一拉
（１）在钉子板上用橡皮筋拉一个长方形。
（２）在钉子板上用橡皮筋拉一个正方形
５、画一画
打开课本１４８页练习三十九第１题， 照样子在方格
图中画出长方形和正方形。
６、看图填空：
７、拼一拼
⑴用２个小正方形拼出一个长方形。
⑵用３个小正方形拼出一个长方形。
⑶用４个小正方形能拼出一个什么图形？
８、折一折
⑴用正方形纸折出２个长方形。
⑵用正方形纸折出４个长方形。
９、找一找（扩散思维练习）
在图中找出有几个正方形？有几个长方形？
四、课堂总结：
【板书设计】
认识长方形和正方形
┏━━━━━━━┓ ┏━━━━┓
┃ ┃ ┃ ┃
┃ ┃ ┃ ┃
┃ ┃ ┃ ┃
┗━━━━━━━┛ ┗━━━━┛
边： 有４条边 有４条边
对边相等 ４条边都相等
角： 有４个角，都是直角 有４个角，都是直角
【教材说明】
１、 学生在一年级第一册中已初步认识长方形和正方
形， 本节课就是在以上感性认识基础上进一步认识长方形
和正方形的特征。
２、根据省教委教材调整意见，第四册删除“初步认
识平行四边形”内容。FileIO Xtra
Version 1.0.4 - 09dec97 CH
FileIO Xtra for Macromedia Director 6.0
=======================================
FileIO provides a set of methods allowing users of Macromedia Director 6.0 to
programmatically access files using the Lingo scripting language. The FileIO
Xtra is a scripting Xtra. The scripting Xtra interface is portable across
all Macromedia products. Hence the FileIO Xtra may be used with Authorware 4.
Using FileIO
============
If automatic opening is desired, place a copy of the FileIO Xtra for your platform
into Application Xtra's folder. If automatic opening is not desired, the Xtra can be
placed anywhere and opened using Lingo's 'openXLib' command. This applies to
projector's as well, the Xtra must be placed in an Xtra's folder in the same folder
as the projector.
Each instance of FileIO can reference a single open file. If multiple files are to
be opened simultaneously, a new instance of FileIO is required for each opened file.
A single instance can be used to open multiple files, as long as the file is closed
before a new file is opened. To create a new instance, use the new() method, defined
below. To dispose of an instance, set the instance variable to 0. All methods that
read from or write to the file must be called after the file has been opened using
the openFile() method. If a new file is to be opened using the same instance, the
file must be closed using closeFile(). Files can be opened in three different modes:
Read, Write and Read/Write. When writing to a file, the contents of the file after
the current position are overwritten.
Example Lingo
set myFile = new(xtra "fileio") -- Create an instance of FileIO
set fileName = displayOpen(myFile) -- Display Open Dialog and return the fileName
openFile(myFile, fileName, 1) -- Open the file
set theFile = readFile(myFile) -- Read the file and return a string to Lingo
closeFile(myFile) -- Close the file
set myFile = 0 -- Dispose of the instance
In this example, we created a new instance and stored it in the variable myFile.
Next, the displayOpen() method is used to display an open dialog to allow a file to
be chosen. The file is returned as a fully-qualified path string to Lingo. The file
is then opened in read only mode, the contents of the file are read, and the file is
closed. Lastly, the instance is disposed of.
Known Problems
==============
The createFile() method does not support relative filenames, or the Lingo '@'
operator in pathnames. This will be fixed in a later version.
The displaySave() method does not directly inform Lingo whether a user is
replacing an existing file. The workaround is to attempt to create the file using
createFile() and check the error code for a "File Already Exists" error.
History
=======
09dec97 (v1.0.4)
Fixed a problem leading to garbage characters appearing at the ends of lines,
or possibly crash.
18apr97 (v1.0.2)
Fixed parenting problem with displaySave() and displayOpen() methods.
Added support for Authorware.
27may96 (v1.0.1)
Added support for double-byte character sets.
Added version() method to report FileIO Xtra version information.
Added getOSDir() to return a full path to the Windows Directory/System Folder.
15mar96 (v1.0.0 Beta)
First public release.
Method Reference
================
The first line of each definition contains the method name, a list of parameters and
thier value types. The internal name of the FileIO Xtra is "fileio". This name is
used whenever referencing the xtra using the form 'xtra "fileio"'.
Note that while Director and projector's can use net-based files by supplying a URL
for a filename, the FileIO Xtra cannot. It is limited to accessesing files available
via filesystems mounted on the local system.
New methods will appear at the bottom of this list.
---
mMessageList( xtra reference )
Returns a list of methods and parameters, as well as a brief explanation of each.
---
new( xtra reference )
This is called to create a new instance of FileIO. The Xtra can be referenced by name
or number. It returns an instance variable used to reference the instance.
---
fileName( instance )
Returns the fileName string of the current open file. The file must be open use this
method.
---
status( instance )
Returns the error code returned by the last method called. The value is returned as
an integer.
---
error( instance, int error )
Returns a readable error string. A numeric error code is passed in as the
second argument. The errors returned can be any of the following:
"OK"
"Memory allocation failure"
"File directory full"
"Volume full"
"Volume not found"
"I/O Error"
"Bad file name"
"File not open"
"Too many files open"
"File not found"
"No such drive"
"No disk in drive"
"Directory not found"
"Instance has an open file"
"File already exists"
"File is opened read-only"
"File is opened write-only"
"Unknown error"
---
setFilterMask( instance, string mask )
Sets the filter mask used by calls to displayOpen() and displaySave(). The filter
mask determines what files to show when displaying an Open or Save dialog. The second
parameter is a string representing the filter mask to set. On Windows, this is a
comma seperated string of file types and associated extensions (e.g. "All
Files,*.*,Text Files,*.TXT"), and a string of types on the Macintosh (e.g.
"TEXTPICT"). On Windows, the filter mask string is limited to 256 characters. On the
Macintosh, you are limited to four four-character types. When a new instance of
FileIO is created, the filter masks defaults to all files. To reset the filter mask to
display all files after it has been set, just pass in an empty string (e.g.
setFilterMask(me, "")).
---
openFile( instance, string fileName, int openMode )
Opens the named file. This call must be used before any read/write operations can
take place. The filename can be either a fully-qualified path and filename, or a
relative filename. The Lingo '@' pathname operator is supported. The openMode
parameter specifies whether to open the file in Read, Write or ReadWrite mode. Valid
Flags are: 0 Read/Write, 1 Read, 2 Write.
---
closeFile( instance )
Closes a file that has been previously opened using the openFile() method.
---
displayOpen( instance )
Displays a platform specific Open dialog allowing a user to specify a file. Returns a
fully-qualified path and fileName to Lingo. The setFilterMask() method can be used to
control what file types are displayed in the dialog.
---
displaySave( instance, string title, string defaultFileName )
Displays a platform specific Save dialog allowing a user to specify a file. Returns a
fully-qualified path and fileName to Lingo. The setFilterMask() method can be used to
control what file types are displayed in the dialog. The string and defaultFileName
parameters allow you to specifiy a default filename to be displayed, as well as title
text for the save dialog.
---
createFile( instance, string fileName )
Creates a file. The fileName must be either a fileName to be created in the current
directory, or a fully-qualified path and fileName. The Lingo '@' pathname operator
and relative paths are not supported. After creating the new file, the file must be
opened before it can be written to.
---
setPosition( instance, position )
Sets the file position of the current open file. The file must be open to use this
method.
---
getPosition( instance )
Gets the file position of the current open file. Returned as an integer. The file
must be open to use this method.
---
getLength( instance )
Gets the length of the currently opened file. Returned as an integer. The file must
be open use this method. The value returned is the length of the file in bytes.
---
writeChar( instance, string theChar )
Writes a single character to the file at the current position. The file must be open
in write or read/write mode to use this method.
---
writeString( instance, string theString )
Writes a string to the file at the current position. The file must be open in write
or read/write mode to use this method.
---
readChar( instance )
Reads the character (either single or double-byte) at the current position and then
increments the position. The character is returned to Lingo as a string. The file must
be open in read or read/write mode to use this method.
---
readLine( instance )
Reads from the current position up to and including the next CR, increments the
position, and returns the string to Lingo. The file must be open in read or
read/write mode to use this method.
---
readFile( instance )
Reads from the current position to the end of the file and returns the file to Lingo
as a string. The file must be open in read or read/write mode to use this method.
---
readWord( instance )
Reads the next word starting at the current position. The file must be open in read
or read/write mode to use this method.
---
readToken( instance, string skipChar, string breakChar )
Reads the next 'token' starting at the current position. Characters matching the
skipChar parameter are "skipped" and the file is read until breakChar is encountered.
The file must be open in read or read/write mode to use this method. This method will
read double-byte tokens as long as the skip and break are single-byte characters. It
will not detect double-byte skip or break characters.
---
getFinderInfo( instance )
Returns the Type and Creator of the current file as a string. This method does
nothing when used under Windows. The file must be open to use this method.
---
setFinderInfo( instance, string typeAndCreator )
Sets the Type and Creator of the current file. The string takes the form of a space
seperated set of TYPE and CREATOR codes (e.g. "TEXT TTXT"). This method does nothing
when used under Windows. The file must be open to use this method.
---
delete( instance )
Deletes the currently opened file. The file must be open use this method.
---
version( xtraRef )
Returns FileIO version and build information. Useful when filing
bug reports, determining installed version while authoring, etc. No practical use beyond this.
---
getOSDir( )
Global method that returns the full path to either the Windows directory, or the System Folder
depending on which OS is currently being used. Does not require a child instance or
Xtra reference to call.
---
