Toshiba T2N - Manual (Page 150)

2. User Program Configuration
User's manual 137
The user program memory can be divided into the system information
storage area and the user program storage area, as shown below.
System information is the area which stores execution control parameters
for executing the user program and user program management information,
and it always occupies 0.5K steps.
The user program is divided by the program types into main program,
sub-program, interrupt programs and sub-routines, depending on the
function.
Of these, the main program is the core of the user program.
On the other hand, when it is difficult to achieve the requested control
functions by the main program alone, sub-program and interrupt
programs are used as required, but need not be provided.
Also, sub-routines are used when repetition of the same process in a
program is required, or in order to see the program more easily by
making one function into a block, but may not be provided if not
required.
2.1
Overview
0.5K steps System information
User program 23.5K steps
User Program Memory Configuration