MATLAB: How i can use the value of a in other function

Question

how i can use the value of a in other function? and my code is here.

function pushbutton1_Callback(hObject, eventdata, handles)
[a , b] = uigetfile({'*.*' , 'all files'});
imread(a);
imshow(a);
% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
v = imread(a);
bw = im2bw(a);

Answer 1

function pushbutton1_Callback(hObject, eventdata, handles)
[a , b] = uigetfile({'*.*' , 'all files'});
imread(a);
imshow(a);
handles.a = a;
guidata(hObject, handles);
% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
handles = guidata(hObject);
v = imread(handles.a);
bw = im2bw(handles.a);

Note: Better use absolute file names with path:

a = fullfile(b, a);