This is an old trick I used to do in the EDIT.COM of DOS to impress my friends. I discovery that some binary instructions could be represented in the text editor.
This is the sequencia to create an executable that prints the CLAUDIA name:
ALT 180 // 180 = B4h = mov AH ALT 02 // 2 ALT 178 // 178 = B2h = mov DL C // C ALT 205 // 205 = CDh = INT ! // ! = 33 = 21h ALT 178 ... L ALT 205 ! ALT 178 A ALT 205 ! ALT 178 D ALT 205 ! ALT 178 I ALT 205 ! ALT 178 A ALT 205 ! ALT 180 // mov AH L // L = 4Ch ALT 205 // INT 21 => exit to DOS !
This will generate this binary file sequence:
B4 02 B2 43 CD 21 B2 4C CD 21 B2 41 CD 21 B2 55
CD 21 B2 44 CD 21 B2 49 CD 21 B2 41 CD 21 B4 4C
CD 21
It is equivalente to this assembly instruction:
MOV AH,02 ; To select subfunction 2, move the appropriate number, 2, to AH.
MOV DL,”A” ; In the interrupt list, it says that the character to output should be
INT 21h ; in register DL. So we move the character to DL.
; Finally when all the registers are set as required, we call the interrupt.
MOV AH,4Ch ; Select the subfunction
INT 21h ; Select a return value (optional but recommended)
; Call the DOS interrupt.
