The less than (<) block produces an output signal of 1
if and only if input signal *x*_{1} is less than input signal
*x*_{2}. Otherwise, the output is 0. On the connectors, “l”
represents *x*_{1} and “r” represents *x*_{2}.

If you right-click the < block, the Boolean block menu appears allowing you to assign a different function to the block.

**1.
Simple if-then-else construct**

Consider a variable *y* such that:

If* t* < 4 then *y* = 1; else *y* = 0

Assume that *t *is simulation time. This system can be
realized as:

By multiplying a constant value 1 with the output of the
< block, *y* is guaranteed to assume a value of 0 until the inequality
is true. When the inequality is true, *y* assumes a value equal to the
output of the * block.

**2.
Modified if-then-else construct**

The previous example can also be realized as:

The key difference in implementation is the use of a merge block rather than a * block. The merge block explicitly depicts the if-then-else structure; the * block is a shortcut and can lead to confusion.