Can we use l,k,z as global variables in GUI rather than using x,y,z ?

I'm working on image steganography code. Here I have used global l, global k, global z in the code. Is that fine or should I use global x, global y, global z ?

[Geoff Hayes]

Gayatri - why are you using global variables at all? Please describe why you feel you need to use them...

[Gayatri B]

I heard that global variables have different purposes like to display image in gui like this. so I used. Can you tell me what should I use ? some part of my code is given below :

function Retrive_Callback(hObject, eventdata, handles)

global l;

h=mod(l,2);

p=zeros(1000,1000);

for x=1:1000

for y=1:1000

if(h(x,y)==1)

p(x,y)=255;

end

end

end

s=im2bw(p);

axes(handles.axes4);

imshow(s);

grid on;

Answer 1

[Guillaume]

You shouldn't be using global variables at all. There's always better ways of doing whatever it is you're doing.

As for the name of global variables, you can use whatever you want. If you do use global variables (which are a major source of bugs) I would recommend using very descriptive names rather than one letter variables.

Obviously, the name must be the same in each unit of code that uses these variables.

[Gayatri B]

I heard that global variables have different purposes like to display image in gui like this. so I used. Can you tell me what should I use ? some part of my code is given below :

function Retrive_Callback(hObject, eventdata, handles)
global l;
h=mod(l,2);
p=zeros(1000,1000);
 
for x=1:1000
    for y=1:1000
        if(h(x,y)==1)
            p(x,y)=255;
        end
    end
end
 
s=im2bw(p);
axes(handles.axes4);
imshow(s);
grid on;

[Guillaume]

You can use the handles structure to pass data between callbacks.

See Share data among callbacks for other ways, all better than global variables.

[Gayatri B]

okay. I want to declare these variables before using it anywhere so I used global.