• C++

using namespace std;
string s;
int x {a % 100};
if (x > 9 and x < 14) s = "th";
else switch (a % 10) {
    case 1: s = "st"; break;
    case 2: s = "nd"; break;
    case 3: s = "rd"; break;
    default: s = "th";
}
s = to_string(a) + s;

• Java

String s;
int x = a % 100;
if (x > 9 && x < 14) s = "th";
else s = switch (a % 10) {
    case 1 -> "st";
    case 2 -> "nd";
    case 3 -> "rd";
    default -> "th";
};
s = a + s;

• Pascal

  if ((a mod 100) in [10..20]) then
    s := 'th'
  else
  case (a mod 10) of
    1: s := 'st';
    2: s := 'nd';
    3: s := 'rd';
    otherwise
      s := 'th';
  end;
  s := a.ToString + s;

• Python

if 9 < (a % 100) < 14: s = 'th'
else:
    match a % 10:
        case 1: s = 'st'
        case 2: s = 'nd'
        case 3: s = 'rd'
        case _: s = 'th'
s = str(a) + s

• Ruby

s = if (a % 100).between?(9, 14) then 
  'th'
else
  case a % 10
    when 1 ; 'st'
    when 2 ; 'nd'
    when 3 ; 'rd'
    else 'th'
  end
end

s = a.to_s + s