System Unit  
The main component 
of 
your IBM Portable Personal 
Computer 
is 
the system unit. 
It 
accomplishes all of the 
processing and controlling operations for your system 
through a set of instructions called a program.  The 
IBM Portable Personal Computer comes with the 
programming language, "IBM BASIC," already 
installed, and most programs are written in that 
language. However, you also can write programs for 
your IBM Portable Personal Computer in several other 
IBM supported programming languages.  Although a 
reference manual for IBM BASIC is included with your 
system unit, prior knowledge 
of 
general programming 
concepts 
is 
very helpful for writing programs for your 
IBM Portable Personal Computer.  In addition, various 
program packages are available at your Authorized IBM 
Personal Computer Dealer to satisfy a variety of your 
business and personal needs. 
The system unit stores data 
on 
the diskette drive using 
an operating system, such as the IBM Disk Operating 
System (DOS).  IBM DOS allows the system unit to 
store and retrieve data from the diskette drive.  The 
DOS 
reference manual and the IBM 
BASIC 
manual 
explain the commands needed to store or retrieve data. 
If 
you choose to write your own operating system, the 
IBM Personal Computer XT 
Technical Reference 
manual 
(PIN 
6936808) will be helpful in providing the 
necessary information. 
System Unit 
3-5