BinaryWrite

BinaryWrite[channel, b] writes a byte of data, specified as an integer from 0 to 255.

BinaryWrite[channel, {b1, b2, ...}] writes a sequence of bytes.

BinaryWrite[channel, "string"] writes the raw sequence of characters in a string.

BinaryWrite[channel, x, type] writes an object of the specified type.

Examples

Write bytes to a file:

stream = OpenWrite["test.bin", BinaryFormat -> True];
BinaryWrite[stream, {72, 101, 108, 108, 111}];
Close[stream];

Please visit the official Wolfram Language Reference for more details.