To create a directoy, we use the function 'CreateDir(c)' where 'c' is of type PChar. In Pascal, there are functions with which you can either create or remove a directory from the hard disk. I know, that this directive is somewhat complicated and hard to be understood but nonetheless useful!īack To Top ⇧ Create and Remove Sub-Directories You can try as many programs as you wish and practice the IO directive with trial and error. That is, you can use it with 'Rewrite()', 'Append()', 'Erase()', and also 'FSearch()'. ![]() The compiler directive could be applied to different file-related functions, similarly as in the program above. Study carefully the program above and run it several times with valid paths and non-valid ones to distinguish well the difference as well as how the compiler directive works!! However, if it is not found there is no need to include a call to Close() on an unopened file and this is done conditionally as shown in the example. ![]() IMPORTANT: if the file is successfully found, the file is opened and you should close it as shown in the program above. If the required file is found the IOResult returns a 0 value, meaning no errors ELSE if not found (IOResult returns a non-0 value) display an error message! Writeln('The first line of the file reads: ',s) Writeln('The file required to be opened is not found!') ![]() Writeln('Enter the file name (including its full path) of the text file (without the extension):') We will still use the readln() and writeln() in order to read and write from/to a text file The concept of how to read a text file is demonstrated below: Program Lesson8_Program1 There are special functions in Pascal that enable us to read or write a text file. We only require a few bytes, don't worry!īack To Top ⇧ Read from a File (file input) So other files may contain more data other than just text data.īefore we proceed with files, please make sure that you have enough hard disk space for our practice, since I am going to demonstrate to save a file to the hard disk!! :) Just kiddin'. Such files cannot be saved as plain text since extra data is needed to store the formatting. However, some programs have various rich text formats in which text maintains a certain format - such as justification, font-face and font colour. Whenever you use a text editor and create a text file, the saved file is written on to the permanent storage. Many text files are saved on permanent storage such as hard disks with the extension. Files have got the advantage of not losing their data after a program terminates (provided that data is saved properly to the file).Ī file can contain either text data or binary data. When we use variables, their data will be lost when the program terminates. This is getting long-winded now, so I'll close with the request for any adjacent commentary on this as I've overworked it in my mind and need a clean take.A file contains data which is stored on a permanent medium. It has a very high operator precedence, and there's no binary ^ operator, so I cannot see how they interact to test the algorithm. ![]() That solves it, I guess, so as another example, the logical not operator, seen in object pascal. In my case, that has been permuted to binary multiplication with -1 as the other operand. The most obvious unary prefix operator would be arithmetic negation, 2 * -3, for instance. Is this algorithm sufficient? I'm unsure. It seems to work well enough, but I cannot find any direct discussion of how prefixing unary operators should be handled. I hope I've sufficiently described that algorithm. If top.precedence > infix.precedence thenĮlse if (top.precedence = infix.precedence) and top.associative then I've been working on an algebraic symbol manipulator that handles numerics and binary operators like +-*/ and ^.
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