Logical operators not working inside while loop

I have wrote conditions inside while loop using logical operators.

my program is

p=12;

while (p~=1) | (p~=2)
imshow(image.jpg);
end

but an infinite loop is running

I am unable to find the bug in this. Please help.

Answer 1

[Sean de Wolski]

Well you never change p so it is always 12!

x = 10;
while x~=1
  x = x-1;
  disp(x)
end

Alternatively you can use a for-loop:

for ii = 10:-1:1
  disp(ii);
end

Answer 2

[Jan]

Yes, of course this is in infinite loop: The value of p does not change inside the loop.

Answer 3

[Niladri]

Thank you Sean de Wolski & Jan Simon.

Now I have wrote a program which is actually required for my project.

I am taking an analog output (as trigger) from DAC. My codes will start working only when matlab receives trigger from DAC.

Codes are:

p=0;
while (p~=128|p~=192)  %2 types of output released by DAC%

p=fread(s,1);
if (p==128)        
imshow('x.jpg'); pause(1); imshow('z.jpg'); pause(2); 
elseif (p==192
imshow('y.jpg'); pause(1); imshow('z.jpg'); pause(2);
end

end

According to the logic used in the previous program this also should run infinite times and that I need. But it is terminating after some time automatically. Please help.