You probably don't want to use 1 (no quotes) for a default value for the squares - when output as a character, that becomes ASCII 1, which is a control character - how it is represented on screen varies depending on where you do it: it might be a weird happy-face looking thing (in a console window), a ^ followed by A (in gVim, for example; or in a telnet window) or nothing visible at all (most other place I can think of).

' ' will print as a space, which is probably more like what you want. The actual numeric value is 32, assuming ASCII (which is pretty safe these days).