C language learning:% d, 2d, 02d, the difference .2d

%d: As a normal output.

%2d: 2 in width is output, the output right-aligned manner. If two is not enough, left the meeting spaces.

%02d: 2 of the same width, alignment to the right. The median is not enough left 0s.

%.2d: From the implementation point of view, with the same% 02d.