Designing Games with Game Maker - YoYo Games

Here are some variables and functions that deal with errors.
error_occurred Indicates whether an error has occurred
error_last String indicating the last error message
show_debug_message(str) Shows the string in debug mode
The following functions exist that allow you to check whether certain variables exist and with
which you can set variables and get their values. In all these functions the variable name is
passed as a string!
variable_global_exists(name) Returns whether a global variable with
the given name (a string) exists.
variable_local_exists(name) Returns whether a local variable with the
given name (a string) exists for the current instance.
variable_global_get(name) Returns the value of the global variable with
the given name (a string).
variable_global_array_get(name,ind) Returns the value of index ind
of the global array variable with the given name (a string).
variable_global_array2_get(name,ind1,ind2) Returns the value of
index ind1,ind2 of the global 2-dimensional array variable with the given name
(a string).
variable_local_get(name) Returns the value of the local variable with the
given name (a string).
variable_local_array_get(name,ind) Returns the value of index ind of
the local array variable with the given name (a string).
variable_local_array2_get(name,ind1,ind2) Returns the value of
index ind1,ind2 of the local 2-dimensional array variable with the given name
(a string).
variable_global_set(name,value) Sets the global variable with the
given name (a string) to the given value.
variable_global_array_set(name,ind,value) Sets the index ind in
the global array variable with the given name (a string) to the given value.
variable_global_array2_set(name,ind1,ind2,value) Sets the index
ind1,ind2 in the global 2-dimensional array variable with the given name (a
string) to the given value.
variable_local_set(name,value) Sets the local variable with the given
name (a string) to the given value.