1 assume cs:codesg 2  3 datasg segment 4     db "Beginner's All-purpose Symbolic Instruction Code.",0 5 datasg ends 6  7 codesg segment 8 begin: 9     mov ax,datasg10     mov ds,ax11     mov si,012     call letterc13     14     mov ax,4c00h15     int 21h16     17 letterc:18     push cx19     push si20     push bx21     22     mov cx,023 ks:    24     mov byte ptr cl,ds:[si]25     jcxz ok26     cmp cl,9727     jb lp28     cmp cl,12229     ja lp30     and cl,11011111B31     mov byte ptr ds:[si],cl32 lp:33     inc si34     jmp short ks35 ok:36     pop bx37     pop si38     pop cx39     ret40     41 codesg ends42 end begin43