# Bitwise Boolean Logic

The KS3 National Curriculum for *Computing* requires that students know
binary and Boolean logic, and also that they are *able to carry out simple operations on binary numbers*. If you understand binary and you understand Boolean logic, then this could be one such operation - it's simply a combination of the two. Bitwise operations convert numbers to their binary equivalents and then apply logical operators to them a bit at a time.

You can change the numbers either by clicking on the 0s and 1s, or by typing numbers into the boxes. Try some examples - e.g. 3 OR 5 = 7. Can you see why? Look at the right-most bits - 1 OR 1 = 1. The next bits give 1 OR 0 = 1, and, in the 4 column, 0 OR 1 = 1. This means that the right-most three bits in the answer are 111 - i.e. 7.

This technique is used to *mask* bits to separate binary flags (amongst other things). Give it a try - enter a number and then AND it with 16; the answer will tell you whether the number includes History.

For a more in-depth discussion of this and other related techniques, look at the *Bitwise Logic* page in the *Mathematics* section.

Why not practice your programming skills by creating a program that uses these techniques? Bitwise logic can be used to convert decimal numbers to binary, or you can use Exclusive-OR to encrypt text. This technique is also used in my traffic light and seven-segment display examples to indicate which lights should be lit for each stage in the sequence. Click here to download some curriculum programming examples.