binary file: what changed

Revision 0 to 1. Removed lines have a minus sign; added lines have a plus sign.

Title: binary file

New		Line
1	+	## Binary file
2	+
3	+	A binary file is suitable for processing files of any size. With binary files, the content of a file is read in character by character. Conversely, the file is written character by character. If a file is opened as a binary file, a character can be changed anywhere in the file. Data of the same type can now be written and read into a file defined with FILE OF as follows:
4	+
5	+	``` pascal
6	+	var
7	+	datFile : File of Byte; // always reads and writes a character
8	+	datFile : File of Char; // always reads and writes a character
9	+	datFile : File of Integer; // always reads and writes two characters
10	+	...
11	+	```
12	+
13	+	Any location in the binary file can be accessed with the SEEK command.
14	+
15	+	## Create file
16	+
17	+	``` pascal
18	+	var
19	+	datFile : File of Char;
20	+	chrContent : Char;
21	+
22	+	begin
23	+	Assignfile(datFile, 'example.txt'); // Assigns the name of the file to the variable txtFile and opens the file
24	+	ReWrite(datFile); // File will be overwritten if it exists
25	+	chrContent := 'A';
26	+	Write(datFile, chrContent); // Write the first character to the new file
27	+	...
28	+	end;
29	+	```
30	+
31	+	## Close file
32	+
33	+	``` pascal
34	+	var
35	+	datFile : File of Char;
36	+	chrContent : Char;
37	+
38	+	begin
39	+	...
40	+	CloseFile(datFile); // closes the file
41	+	end;
42	+	```
43	+
44	+	## Add a character to the end of an existing file
45	+
46	+	For binary files, a character can be added to the end of a file using the Seek command.
47	+
48	+	``` pascal
49	+	var
50	+	datFile : File of char;
51	+	chrContent : Char;
52	+
53	+	begin
54	+	AssignFile(datFile, 'example.txt');
55	+	Reset(datFile); // Sets the file pointer to the beginning of the file
56	+	Seek(datFile, FileSize(datFile)); // Determines the end of the file and sets the file pointer to the end
57	+	chrContent := 'b';
58	+	Write(datFile, chrContent); // Write another character at the end of the file
59	+	...
60	+	```
61	+
62	+	## Replace a character in an existing file
63	+
64	+	For binary files, you can use the Seek command to replace a character anywhere in the file.
65	+
66	+	``` pascal
67	+	var
68	+	datFile : File of Char;
69	+	chrContent : Char;
70	+
71	+	begin
72	+	AssignFile(datFile, 'example.txt');
73	+	Reset(datFile); // Sets the file pointer to the beginning of the file
74	+	Seek (datFile, 1); // Set the file pointer to the _second_ character in the file
75	+	chrContent := 'f';
76	+	Write(datFile, chrContent); // Overwrite the second character in the file
77	+	...
78	+	```
79	+
80	+	## Read file completely
81	+
82	+	``` pascal
83	+	var
84	+	datFile : File of Char;
85	+	chrContent : Char;
86	+
87	+	begin
88	+	AssignFile(datFile, 'example.txt');
89	+	Reset(datFile);
90	+
91	+	while not eof(datFile) // keep reading as long as there is data to read
92	+	do begin
93	+	read(datFile, chrContent); // reads a single character into chrContent variable
94	+	...
95	+	end;
96	+
97	+	CloseFile(datFile);
98	+	end;
99	+	```
100	+
101	+	## See also
102	+
103	+	- [[File types]]
104	+
105	+	---
106	+	From the Free Pascal wiki, page "binary file", as it stood on 2022-01-28 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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