# Computer Science

#1
I don't understand how to produce a truth table for a logic gate, if anyone could help that would be great.
0
3 years ago
#2
I'll be happy to help! Just a quick couple of questions: What level are you studying at? (GCSE or other) What logic gates are you aware of? Do you understand how logic gates work?
0
#3
I am doing IGCSE and it is saying about the different logic gates and then it asks me to find out why: x = (a.b) + (a.b) or something like that but i don't understand what it means.
0
3 years ago
#4
(Original post by bubsy2005)
I am doing IGCSE and it is saying about the different logic gates and then it asks me to find out why: x = (a.b) + (a.b) or something like that but i don't understand what it means.
To produce a truth table, you need to write the inputs firstly. When there are two inputs, there are always 4 possible combinations: 0 and 0, 1 and 0, 0 and 1, 1 and 1. So, write the inputs for a and b out. Then, in a column, write down what a.b is. Because . means and, the column for a.b should be 0 unless both inputs are 1. The problem here can be simplified by the Idempotent Law: effectively, anything and itself is itself, and anything or itself is itself.

It might be easier to watch a video which visually shows this.
1
3 years ago
#5
I find that a lot of the time truth tables can actually be derived so you don't have to remember them, like if you know what or gate does them you can produce the outputs from them as long as you remember it also turns on when a 1 and 1 is produced unless it is an xor gate.
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