High-level Programming Language (Pascal)

Text File

• is a collection of alphanumeric characters
• is ended with the character <eof> (end-of-file)
• all file_variables should be declared at the var declaration
  
  　e.g var infile, outfile : text;

Relevant Procedures

• assign (file_variable, 'external_file')
  • is used to associate a file variable with the external file
  • e.g. assign (infile, 'DataIn.txt');
    • establish a link between the file_variable (infile) and the external_file (DataIn.txt)
      
       
• reset (file_vaiable)
  • to open a file for input (reading)
  • e.g reset (infile);
    • to open the file (infile) for input
    • set the file pointer to the beginning of a file
    • file pointer is a marker that points to the next character to be processed in a file
      
       
• read (file_vaiable, input_list) / readln (file_vaiable, input_list)
  • input_list is used to store the data
  • types of input_list variables should be integer, real, char, string
    
    
• rewrite (file_variable)
  • to open a file for output (writing)
  • e.g rewrite (outfile);
    • to open the file (outfile) for output
    • set the file pointer to the beginning of a file
    • if the external file (DataOut.txt) does not exist then an empty file (DataOut.txt) will be created
    • if the file already exists and is not an empty file then rewrite statement will erase all the data in the file (DataOut.txt)
      
       
• write (file_variable, output_list) / writeln (file_variable, output_list)
• close (file_variable)
  • to close the file
  • force the buffer to proceed the transfer (writing the data into the external file)
  • all opened input files and output files must be closed if they will not be reused in the program

Relevant Function

• eof (file_variable)
  • to determine whether the character is an end-of-file character
  • any attempt to read data beyond the <eof> will cause a run-time error
    

High-level Programming Language (Pascal)

Arrays

• structured data type (e.g. array and record)
• can store a collection of data items of the same type ......
  
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High-level Programming Language (Pascal)

String Procedures

• val (<InStr>, <Num>, <ErrorCode>)
  • converts a <InStr> to its numeric equivalent
  • if the......
    
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High-level Programming Language (Pascal)

String Functions

• length (<InStr>)
  • return the length of a <InStr> (i.e. the number of characters in the string)
  • for ......
    
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High-level Programming Language (Pascal)

Basic Operations on Strings

Assignment

• for example,
  

  　Name := 'Chan Tai Man';
  　Class := 'F4A';
  　Address := 'Rm&......
  
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