MATLAB Programming

Variables
Creating Global Variables. Each function that uses a global variable
must first declare the variable as global. It is usually best to put global
declarations toward the beginning of the function. You would declare global
variable MAXLEN as follows:
global MAXLEN
If the M-file contains subfunctions as well, then each subfunction requiring
access to the global variable must declare it as global. To access the variable
from the MATLAB command line, you must declare it as global at the
command line.
MATLAB global variable names are typically longer and more descriptive
than local variable names, and often consist of all uppercase characters. These
are not requirements, but guidelines to increase the readability of MATLAB
code, and to reduce the chance of accidentally redefining a global variable.
Displaying Global Variables. To see only those variables you have declared
as global, use the who or whos functions with the literal, global.
global MAXLEN MAXWID
MAXLEN = 36; MAXWID = 78;
len = 5; wid = 21;
whos global
Name Size Bytes Class
MAXLEN 1x1 8 double array (global)
MAXWID 1x1 8 double array (global)
Grand total is 2 elements using 16 bytes
Suggestions for Using Global Variables. A certain amount of risk is
associated with using global variables and, because of this, it is recommended
that you use them sparingly. You might, for example, unintentionally give
a global variable in one function a name that is already used for a global
variable in another function. When you run your application, one function
may overwrite the variable used by the other. This error can be difficult to
track down.
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