Fax Autograph Conditional with airSlate SignNow

Fax autograph conditional

we're going to do a demonstrate and demonstration on the importance of choosing the proper jumps okay there are the sign jumps and there are unsigned jumps and it's important that you choose the right one down here in Notepad I have two values I have 7f and I have 80 I've expanded them out into their binary representations and you see that 7f has a zero in the most significant bit and 880 has a one in the most significant bit if these two numbers are treated in our program as unsigned numbers 7f corresponds to the value of 127 and 80 corresponds to the value of 128 if they're unsigned numbers are both positive okay if we're treating these same bit values sign numbers then 7f still represents positive 127 but now 80 hex represents minus 128 I leave this to you to verify this it with notepad with your calculator or by doing the two's complement okay so now if we go to debug we find out our registers are IP is at 100 and let's just put in some funny code some play code and figure out the difference between jump of above and jump of greater than okay the first instruction I'm going to do is move a l7f okay so I'm moving this pattern here into the byte to register al following that I'm going to compare al with the value the immediate value of 80 okay so this is equivalent to if I write it essentially I'm going to be going if al and I'm going to go if al is greater than 80 if I'm giving this piece of code here that's the seed kind of idea the see representation okay I have a choice now of either using jump up above or jump greater than and it's important to choose the right one based on the kind of data that al contains if it contains unsigned data then you want to go jump above you want go jump above to some location and I'm just gonna put it to a a okay so it's going to jump to somewhere else so if al is above 80 it will jump to a a otherwise it will continue on and execute the following instruction at 106 is however okay so let's just see what happens there can you predict what will happen al is 7 F which is 127 we are looking at J a so that means we are treating al + 8 0 as unsigned numbers is 127 above 128 no it's not okay so we shouldn't take the jump let's execute this code okay so we'll first go we execute its move o now al contains 7f we are going to execute to compare and the purpose of the compare is nothing changes nothing changes or nothing changes nothing changes except for the flags the purpose of the compare instruction is to change the flags okay and of course the IP changes because we've executed an instruction we are now going to execute jump of above jump of above is 7f above 80 what's the instruction has it taken and gone off to some other location or is it simply fallen down and executed the next instruction it's fallen down and in there it did not take the jump okay so if al contains an unsigned value we go jump above what if instead okay I'll let me just show you this on assemble CS : 100 this is the code that we have so far at CS : 100 we've got move a l 7f we've got the compare and we've got the jump up jump up above I'm going to now replace this with jump if greater than and we're gonna re execute the same code so I'm gonna go assemble at CS : 104 and I'm gonna go jump if greater then a a so now let's go on assemble CS : 100 see my program now it's the move it's the compare and then it's the jump of greater than I am now treating the same value of 7f and 80s sign numbers we're going to register set the IP back to 100 so we're gonna start a game okay let's look at our registers our IP is 100 and we're going to start again we're going to re-execute so al still contains 7f now we're gonna execute the compare and the same flags are Sat okay but now I'm gonna take 104 and it's going to do JG and this time we're looking is 127 above minus 128 positive is above negative so yes so we should be taking the jump so we should not go to address 106 in fact our IP is at zero zero zero zero zero a a we are no longer at CS : 106 so to review when we did we did J a we did not take the jump but when we did JG we did take at the jump just by choosing signed or unsigned you change the behavior code we did not change the data we changed the code and the code operates differently so if you're given the C syntax like this if a elk is greater than 80 you have to choose either J a or je je G and the way you choose it is based on the type of the data if it's signed you have to use JG if it's unsigned you have to use J a good luck in your programming