Editing Dc (computer program) (section)

===Conditionals===
Finally, we can use this macro mechanism to provide conditionals. The command <code>=r</code> pops two values from the stack, and executes the macro stored in register <code>r</code> only if they are equal. So this prints the string <code>equal</code> only if the top two values on the stack are of equal value:

<pre>
[[equal]p] sr 5 5 =r
</pre>

Other conditionals are <code>></code>, <code>!></code>, <code><</code>, <code>!<</code>, <code>!=</code>, which execute the specified macro if the top two values on the stack are greater, less than or equal to ("not greater"), less than, greater than or equal to ("not less than"), and not equals, respectively. Note that the order of the operands in inequality comparisons is the opposite of the order for arithmetic; {{kbd|5 3 -}} evaluates to {{code|5 - 3 {{=}} 2}}, but {{kbd|5 3 <t}} runs the contents of the {{kbd|t}} register because {{code|3 < 5}}.