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Unformatted text preview: ffer over a standard serial or parallel device?
7. What is the purpose of the 8259A PIC controller?
8. What are the main differences between Wi-Fi and Bluetooth? 2.5 Input-Output System Tip: Because computer games are so memory and I/O intensive, they push computer performance to the
max. Programmers who excel at game programming often know a lot about video and sound hardware,
and optimize their code for hardware features. 2.5.1 Levels of I/O Access
Application programs routinely read input from keyboard and disk ﬁles and write output to the
screen and to ﬁles. I/O need not be accomplished by directly accessing hardware—instead, you
can call functions provided by the operating system. I/O is available at different access levels,
similar to the virtual machine concept shown in Chapter 1. There are three primary levels:
• High-level language functions: A high-level programming language such as C++ or Java
contains functions to perform input-output. These functions are portable because they work
on a variety of different computer systems and are not dependent on any one operating
• Operating system: Programmers can call operating system functions from a library known
as the API (application programming interface). The operating system provides high-level operations such as writing strings to ﬁles, reading strings from the keyboard, and allocating blocks of
memory. For More BS-IT Books, Notes & Assignments visit: www.bsit.zxq.net 2.5 Input-Output System
Downloaded From: www.bsit.zxq.net 53 • BIOS: The Basic Input-Output System is a collection of low-level subroutines that communicate directly with hardware devices. The BIOS is installed by the computer’s manufacturer and
is tailored to ﬁt the computer’s hardware. Operating systems typically communicate with
Device Drivers Device drivers are programs that permit the operating system to communicate
directly with hardware devices. For example, a device driver might receive a request from the
OS to read some data; the device dr...
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- Winter '13