str2 db ? is not an empty string. db stands for “define byte”, and that ? means single uninitialized byte. The db “0neWord” is assembler’s convenience, it will compile into series of bytes defined as ‘0’, ‘n’, ‘e’, …, ‘d’. There’s no such thing as “string” type in assembler, everything is compiled into machine code, … Read more
why can’t I move 8 bit variable into much larger 16 bit register? Becase the machine code MOV instruction needs both the source operand and destination operand to be the same size. This is needed because a MOV instruction by itself doesn’t specify how to fill the remaining bits of the larger destination register. To … Read more
One simple pseudo random number generator multiplies the current number by 25173, then adds 13849 to it. This value now becomes the new random number. If you started from the system timer like you did (this is called seeding the random number generator), this series of numbers will be random enough for simple tasks! MOV … Read more
I am assuming: PC VGA x86 MS DOS platform It does not really matter if real or emulated unless you want low level IO access which might not work properly on emulation like DOSBOX … Video/Text modes So to switch between video and text modes you need to use VGA BIOS: mov ax,mode ; here … Read more
See the x86 tag wiki for the instruction set reference manual, and many good links to reference material and tutorials. It takes enough code to split up an integer into ASCII digits that you should factor it out into a function. This is an optimized and bugfixed version of @hobbs’s print2Digits function. (I also bugfixed … Read more