In BF, I know you can add and subtract with the
Multiply 4 and 4
Here is a generic looking routine to multiply two numbers in bf. Taken from here.
Multiply a value by another value This requires multiple copies and nested loops.
Copy first operand to a work location Move to work location and enter a loop Move to second operand and copy to a work location Move to second work location and enter a loop Move to result location and increment Move to second work location and decrement Loop until second work location equals zero Move to first work location and decrement Loop until first work location equals zero
Multiply three (a[p]) times five (a[p+1]) and place the result in a[p+2].
+++>+++++< [>>>+>+<<<<-]>>>>[<<<<+>>>>-]< [<< [>>>+>+<<<<-]>>>>[<<<<+>>>>-]< [<<+>>-] <-]
Some further reading here