Flowchart
Flowchart
[A flow chart is shown with two boxes and two arrows. The first box rectangular:] Start
[From the first box there is a short arrow straight down to a diamond shaped box:] Hey, wait, this flowchart is a trap!
[An arrow continues down below from the bottom corner of the diamond box, where there is labeled, and quickly it turns left (in the direction of the arrow), going out under the diamond and then turns left two more times to end up on the right corner of the same box where the arrow points back again.] Yes

Flowcharts are diagrams used to show the logical flow of an algorithm , process, or program. Flowcharts are a recurring theme in xkcd . In this comic, Randall uses the fact that flowcharts can indeed be used to show a loop in the procedure: in this case, the reader will theoretically become trapped in a loop of reading the text in the diamond, following the line marked "YES," and ending back up in the diamond. Those familiar with flowcharts will notice though that, while diamonds usually contain decision questions (which can be answered multiple ways), the diamond here actually includes a statement instead.
The title text contains a suggested solution to the loop: the way to escape the loop is to use a marker and add an additional "NO" arrow proceeding from the diamond to a rounded box labelled "END" before you start the algorithm at "START." This suggests that the decision question in the diamond could more properly be phrased as "Is this flowchart a trap?" However, to follow this suggestion, you would need to actually have the marker that you are about to write instructions to go get. Thus, you must also add the instruction "get a marker" somewhere before the flowchart actually begins (before "START"), so that you actually have the marker by the time you get to the flowchart in the comic. And since you did not have a marker and could thus not write this way out, you are still trapped!
Of course, the reader could disregard the algorithm, but this would break the conventions of following the flowchart. This is perhaps part the comic's purpose - to suggest that a problem cannot be solved from within the confines of its own conventions.
Randall has made use of flowcharts before, and previously released another comic named 518: Flow Charts .
[A flow chart is shown with two boxes and two arrows. The first box rectangular:] Start
[From the first box there is a short arrow straight down to a diamond shaped box:] Hey, wait, this flowchart is a trap!
[An arrow continues down below from the bottom corner of the diamond box, where there is labeled, and quickly it turns left (in the direction of the arrow), going out under the diamond and then turns left two more times to end up on the right corner of the same box where the arrow points back again.] Yes
