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filehandle/stream = a valid variable set with the OpenFile, ReadFile command, or OpenTCPStream (v1.52+)
mybyte = can be an Integer or a floating point number, but only values between 0 and 255 will be stored faithfully. |
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Once you've opened a disk file (or stream) for reading, use this command to write a single byte at a time to the file/stream. Note, a byte is an integer that can take the values 0..255 and occupies 8 bits of storage. Since characters are stored as byte values this function can be used to create a text file one character at a time.
Advanced notes: The number that is stored by WriteByte is actually the least significant byte of an integer so negative numbers and numbers above 255 will still have a value between 0..255. Unless you understand how 32 bit integers are stored in 2's compliment notation this will seem strange but it is NOT a bug. Streams can only be used in Blitz Basic v1.52 or greater. |
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; Reading and Writing a file using ReadByte and WriteByte functions
; Initialise some variables for the example Byte1% = 10 ; store 10 Byte2% = 100 ; store 100 Byte3% = 255 ; store 255 ( the maximum value that can be stored in a Byte ) Byte4% = 256 ; try to store 256 this will end up as 0 ( i.e. 256 - 256 = 0 ) Byte5% = 257 ; try to store 257 this will end up as 1 ( i.e. 257 - 256 = 1 ) Byte6% = -1 ; try to store -1 this will end up as 255 ( i.e. 256 -1 = 255 ) Byte7% = -2 ; try to store 256 this will end up as 254 ( i.e. 256 - 2 = 254 ) Byte8% = Asc("A") ; Store the ASCII value for the Character "A" ( i.e. 65 ) ; Open a file to write to fileout = WriteFile("mydata.dat ") ; Write the information to the file WriteByte( fileout, Byte1 ) WriteByte( fileout, Byte2 ) WriteByte( fileout, Byte3 ) WriteByte( fileout, Byte4 ) WriteByte( fileout, Byte5 ) WriteByte( fileout, Byte6 ) WriteByte( fileout, Byte7 ) WriteByte( fileout, Byte8 ) ; Close the file CloseFile( fileout ) ; Open the file to Read filein = ReadFile("mydata.dat") Read1 = ReadByte( filein ) Read2 = ReadByte( filein ) Read3 = ReadByte( filein ) Read4 = ReadByte( filein ) Read5 = ReadByte( filein ) Read6 = ReadByte( filein ) Read7 = ReadByte( filein ) Read8 = ReadByte( filein ) ; Close the file once reading is finished CloseFile( filein ) Print "Written - Read" Write Byte1 + " - " : Print Read1 Write Byte2 + " - " : Print Read2 Write Byte3 + " - " : Print Read3 Write Byte4 + " - " : Print Read4 Write Byte5 + " - " : Print Read5 Write Byte6 + " - " : Print Read6 Write Byte7 + " - " : Print Read7 Write Byte8 + " - " : Print Chr$( Read8 ) WaitKey() |