# Introduction¶

The C++ library kitty provides data structures and algorithms for truth table manipulation. A truth table is represented in terms of 64-bit words, where each bit in the word represents a function value. For example, the truth table for the function $$x_0 \land x_1$$ is 0x8 (which is 1000 in base 2) and the truth table for the function $$\langle x_0x_1x_2\rangle$$ is 0xe8 (which is 1110100 in base 2). A single 64-bit word can represent functions with up to 6 variables. To store functions with 7 variables, one needs two words, for 8 variables one needs 4 words, and so on.

Two main data structures are provided in kitty to represent truth tables: static_truth_table and dynamic_truth_table. The choice to take which depends on whether one knows the number of variables at compile-time or not. The structure static_truth_table is parameterized by a template argument for the number of variables, dynamic_truth_table retrieves this information as constructor argument.