Byte

A byte is an unsigned integer in the range of 0..255. A byte is 8 bits long. A byte and a char are virtually the same thing as of version 3 of FPC.

Valid values

The key difference is, a byte can only be referred to as a numeric type, while a char can be used as a character, or as part of a string type, and cannot be used in an arithmetic expression. A byte will always be the same size as an ansiChar, but in the future char may be considered a synonym for wideChar, not ansiChar.

For example:

program byteDemo(input, output, stderr);

var 
    foo: byte;
    bar: char;

begin
    // those two assignments are physically the same
    foo := 65;
    bar := 'A';
    
    // although they are the same action,
    // the following would be illegal
    //foo := 'A';
    //bar := 65;
end.

The use of byte or byte as a data type provides better documentation as to the purpose of the use of the particular variable.

Standard functions

Conversion to and from character

The byte type can be coerced to char by using the chr function. Char type values can be coerced to byte by using the ord function.

The above program corrected to legal use:

program ordChrDemo(input, output, stderr);

var
    foo: byte;
    bar: char;

begin
    foo := 65;
    bar := 'A';
    
    foo := ord('A');
    // chr(65) is equivalent to #65
    bar := chr(65);
    bar := #65;
    
    // alternatively: typecasts
    // typecasts of constant expressions
    // are guaranteed to happen at compile-time
    foo := byte('A');
    bar := char(65);
end.

String representation

The binStr function from the system unit can be used to get a string showing the binary representation of a byte:

program binStrDemo(input, output, stderr);

var
    foo: byte;

begin
    foo := 10;
    writeLn(binStr(foo, 8));
end.

The output is:

00001010

A more versatile function is intToBin provided by the strUtils unit.

From the Free Pascal wiki, page "Byte", as it stood on 2022-05-26 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.