Old assembly program

gistfile1.txt

0AEA:0100 mov cx,0  # move 0 into CX
0AEA:0103 mov ah,1  # move 1 into AH
0AEA:0105 int 21    # interrupt: read character (AH=1), drop in AL
0AEA:0107 push ax   # push AX (AH, AL) onto stack
0AEA:0108 inc cx    # increment CX
0AEA:0109 cmp al,20 # compare AL with 0x20 (space character)
0AEA:010B jnz 105   # jump if not zero to 0105
0AEA:010D pop dx    # pop stack into DX
0AEA:010E sub dx,20 # subtract 0x20 from DX (making characters uppercase)
0AEA:0111 mov ah,2  # mov 2 into AH
0AEA:0113 int 21    # interrupt: output character (AH=2) from DL (DX)
0AEA:0115 loop 10D  # decrement CX and if 0 then continue, else goto 010D
0AEA:0117 int 20    # exit program

This program should take characters lowercase until a space character, 
make them uppercase, and print them backwards: hello<space> becomes OLLEH

This program is run from DEBUG in MS-DOS.