Computing Now and Future (1/3) • Nowadays, computer systems come in a variety of sizes, shapes and computing capabilities, from the smallest handheld personal digital assistant (PDA) to the largest multiple-CPU mainframe for the enterprise. • The trends of computing are smaller, faster, more reliable, lower in cost, easier to maintain, and more interconnected within computer networks. Computer Categories (1/2) We shall classify computers based on their applications. • A. Handheld Computers • B. Personal Computers • C. Network Servers • D. Mainframes • E. Supercomputers Computers can also be classified according to size and power. • Microcomputers ˇV refer to handheld computers, personal computers, workstation-class computers and low-end network servers • Midrange computers ˇV refer to high-end network servers and multi-user systems • Mainframes ˇV refer to enterprise servers and supercomputers Handheld Computers (1/2) A Handheld computers • is also called a personal digital assistant (PDA) • commonly used as an electronic appointment book, address book, calculator and notepad • uses a touch screen, pen-based handwriting recognition, keypad or voice recognition technologies • can be connected to a personal computer to synchronise information Personal Computers (1/2) A Personal Computer • is a single-user computer • is used in a wide variety of applications, such as word processing, photo-editing, e-mail and Internet access • is a workstation when used as a client on a network Personal Computers can be further categorised into: • 1. Notebook Computers • 2. Desktop Computers Personal Computers (2/2) A workstation-class computer is designed for specialised tasks such as medical imaging and computer-aided design. Notebook Computers (1/2) A Notebook computer • is also called a laptop computer • is a portable personal computer • encases the processing unit and input, output, storage devices An alternative design of notebook computer called tablet PC • allows input by handwriting with a special pen on the LCD display Desktop Computers (1/2) A Desktop Computer • is a personal computer with a system unit connected to peripheral devices • can be placed entirely on a desk A system unit houses „« motherboard „« CPU „« main memory „« interface cards „« power supply „« storage devices, etc Network servers (1/3) A Network server • is a computer that serves other computers • any computer can be configured to perform the work of a server Mainframes (1/3) A Mainframe • is large, fast, powerful and expensive computers, typically working in time-sharing mode • has a huge main memory to store all the programs of users at the same time • with centralised control, highly reliable, strong data security Mainframes (3/3) Multi-user modes • allow multiple users to access the system at the same time • differences between multi-user modes: ˇV In mainframe-based networks „« major processes are done by the mainframeˇ¦s CPU „« dumb terminals have limited processing power ˇV In client/server networks „« end user processes are handled by workstations „« the major tasks of a server are to provide resources, enforce securities and coordinate among various CPUs