2--x86 Processor

Io need not be accomplished by directly accessing

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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 system. • 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 the BIOS. 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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