Code is supposed to be written in upper case because it is more readable.
Actually, it is not. Pascal is case-insensitive, and there was a recognition during the 1980s that lowercase was easier to read quickly because there was more variation in letter shape: characters didn't do their best to fill an entire 5x7 (or whatever) cell.
Modula-2, which Wirth worked on after Pascal, requires uppercase reserved words (and I think is case-sensitive); I can't speak for his later languages, but quite frankly I like the Modula-2 convention. Ada is case-insensitive, C etc. are case-sensitive and lean towards lowercase.
Wirth's experience before Pascal was mostly on computers with 6-bit character sets, which quite simply did not have lowercase characters (but often did have special characters for greater-than-or-equal comparisons etc.), as well as an arrow for assignment.
And older passports, bills etc. were uppercase because they were produced using high-speed (>= 600LPM) drum printers where the smaller the character set the faster they could run.
MarkMLl