Mọi người thường muốn để gửi các tập tin tùy ý, tuy nhiên, và gửi văn bản bao gồm các phông chữ, màu sắc, và định dạng khác. Ba cách tiếp cận để xử lý yêu cầu này thường áp dụng: UUE, định dạng MIME, và HTML: ✦ người dùng sử dụng mã hóa (UUE) - Có thể viết lại các dòng dữ liệu nhị phân mà bạn muốn gửi khác nhau. | 332 Part VII Integration Power supply Processor under fan external drive bays I O Memory DVD writer PCI and AGP bus .5-inch external bays Video card display Disk drives Figure 21-3 Computer case elements 2004 Barry Press Marcia Press Desktop PC cases come in a range of sizes from small ones with limited expansion capability to floor-standing monsters able to hold multiple systems. It s important to think through the expansion you might want to do before you buy a new case or new complete system because it s going to require drastic measures if you want to exceed the space or cooling available in the case. The size of the case also affects how hard the system is to work inside because small cases are almost always cramped and hard to work with and tend to force haphazard cable layouts that themselves complicate access and service. Large cases are much easier to work with have more expansion capability and have better airflow to aid cooling but aren t as easy to fit into your office home or home theater. Chapter 21 Cases Cooling and Power 333 Airflow and heat buildup Airflow cools nearly every desktop computer sold today and is created by fans in the case itself and in the power supply. How much air pressure the fans create and how much air resistance the components and the shape of the case create determines how effective the cooling will be. Very small cases with limited airflow may be incapable of cooling faster processors video cards and disks that generate a lot of heat. We measured the power consumption and temperature rise in three different systems to see how effective their fans and cases were at removing heat. Table 21-1 shows the results of those measurements. System A was a full-size tower System B a mini-tower and System C a full-size tower with auxiliary fans to improve airflow. System D is the PC you ll see how to build in Chapter 25. Degrees per watt the right-hand column in the table is the measure of how well a case cools the electronics .
