PROCEDURE append( var file_variable : text) If the drive or path doesnÆt exist, a ô path not foundö RTE occurs. If, for some reason, the physical file linked to the file variable doesnÆt exist when this procedure is called, a run-time error occurs saying ô file not foundö. This procedure opens the text file for input after this statement you will be able to use the read and readln procedures (about which more later). PROCEDURE reset( var file_variable : text) That is, wether you want to read from it, write to the end of it, or overwrite its contents. Now we have a variable, linked to a file, with wich we can perform all text file operations we want.įollowing the assign statement, one of three procedures can be called to let DOS know how youÆre going to use the file. If the drive, path and/or file doesnÆt exist, no error occurs. If the filename doesnÆt mention a path, the current directory is assumed.

Also, a complete path cannot be longer than 68 characters. This rule says that a file or directory name consists of at most 8 characters (only letters, digits and a limited set of special characters are allowed), optionally followed by a period and an extension of at most 3 characters (same constraints as for the first part). The first parameter is the variable in which the file information will be stored, the second parameter is a string, containing a correct DOS file name that follows the 8.3 rule. PROCEDURE assign( var file_variable : text filename : string ) Before any of these operations can be performed, however, a physical file on a disk must be linked with a Turbo Pascal variable in which the name, the status and some attributes of the file will be stored during the run of a program. Secondly, the basic operations that can be performed on a text file are: creating a file, writing to a file, closing one, reopening a file, reading from a file and appending to one. To be able to use text files in a program, you must first include the unit dos to your program and then you must declare one or more variables that represent text files: If you want to read in some text you previously wrote to a file, you must close it first and reopen it for reading ItÆs the same the other way round: before writing something to a file that is opened as readable, you must close it and open it again as writable. Turbo Pascal offers some procedures to handle such files and itÆs these procedures I will describe here.įirst of all, a text file in Turbo Pascal is a monodirectional file which means you can only read from it or only write to it, but not both at the same time.

Question: What are text files and how can I use them?Ī text file is, obviously, a file that contains plain text.

Variables en turbo pascal