第六章The System Unit.pptVIP

第六章 The System Unit Desktop system units typically contain the systems electronic components and selected secondary storage devices. Input and output devices, such as a mouse, keyboard, and monitor, are located outside the system unit. This type of system unit is designed to be placed either horizontally or vertically. Vertical units are often called tower models. Desktop (tower model) Notebook system units are portable and much smaller. These system units contain the electronic components, selected secondary storage devices, and input devices (keyboard and pointing device). Located outside the system unit, the monitor is attached by hinges. Notebook system units are often called laptops. Notebook Tablet PC system units are similar to notebook system units. Tablet PCs are highly portable devices that support the use of a stylus or pen to input commands and data. There are two basic categories: convertible and slate. The convertible tablet PC is effectively a notebook computer with a mon-itor that swivels and folds onto its keyboard. The slate tablet PC is similar to a notebook computer except that its monitor is attached to the system unit and does not have a keyboard integrated into the system unit. Convertible tablet PC Slate tablet PC Handheld computer system units are the smallest and are designed to fit into the palm of one hand. Also known as palm computers, these systems contain an entire computer system, including the electronic components, secondary storage, and input and output devices. Personal digital assis-tants (PDAs) are the most widely used handheld computers. PDA Binary codes ASCII, pronounced “as-key,” stands for American Standard Code for Information Interchange. This is the most widely used binary code for microcomputers. For example, the number 3 is represented in ASCII code as 0011 0011 EBCDIC, pronounced “eb-see-dick”，stands for Extended Binary Coded Decimal Interchange Code. It was developed by IBM and is used primarily for large computers.