An open source programming font released by Adobe, made with the intent of maximizing usability and avoiding common design flaws in monospaced fonts.
As much as choice of a font is subjective there are important criteria to consider when choosing a programming font. The characters should be clear, easy to read, in cases of clashing ones such as 1, l, i or O, o, 0 easily distinguishable, differences between different kinds of brackets, quotes and parentheses should be clear, punctuation should be emphasized and they shouldn't break up words or sentences due to uneven character widths.
There are two ways fonts are drawn - as bitmaps or as vectors. Vector fonts allow more efficient scaling, but for screens with resolution below 720p it might be worth considering bitmap fonts as they are generally more legible at smaller sizes on low-resolution screens.