outsourced IT support Very few modern computers or computer-based devices (which includes cell phones, iPods, and automobile computers, to name just a few possibilities) operate independently. Instead, they are tied to other computers directly, by modem, or through a network connection of some sort. The computers may be located physically close to each other, or they may be separated, even by thousands of miles. To work together, computers must have means to communicate with each other. The communication component requires both hardware and software to achieve this goal.
Outsourced IT support The validity of our general description is true
outsourced IT support Our general description of the computer is valid for all general-purpose computer systems, and also for most devices with computers embedded in them, regardless of brand name or size. In more general terms, every computer system consists of a CPU, or central processing unit, where all the processing takes place; memory to hold the programs and data while they are being processed; and some form of input and output, usually one or more keyboards and flat-screen display devices plus one or more forms of long-term storage, usually disks, CDs or DVDs, and USB or SD plug-in memory. Most modern computer systems provide more than one CPU (or ‘‘core’’) within the computer system. A single CPU can process only one instruction at a time; the use of multiple CPUs can increase processing speed by allowing instructions that do not affect each other to be executed in parallel.
outsourced IT support Additional hardware components physically connect computers together into multiprocessing systems, or clusters, or networks, or, via telephone, satellite, or microwave, to computers at other remote locations. A communication channel provides the connection between computers. The channel may be a wire cable, a fiber-optic cable, a telephone line, or a wireless technology, such as infrared light, cellular phone, or radio-based technology such as Wi-Fi or Bluetooth. Special I/O hardware, consisting of a device such as a modem or network interface card (NIC) within the computer, serves as an interface between the computer and the communication channel. There may be additional hardware within the channel itself
outsourced IT support The communication component also requires additional software within the operating system of each computer to make it possible for each computer to understand what the other computers that they are connected with are saying. This software establishes the connections, controls the flow of data, and directs the data to the proper applications for use
outsourced IT support The validity of our general description is true regardless of how complex or simple the computer system may seem. As a specific example, the large z10 EC IBM mainframe computer shown in Figure 1.10 can provide complex Web services to thousands of users at a time. IBM mainframes can have dozens of CPUs working together, with up to 1.52 terabytes (TB) of primary storage. They are capable of executing instructions at a rate of tens of billions of instructions per second!
outsourced IT support The powerful z/OS operating system can keep track of hundreds or thousands of simultaneous users and divides the time among them to satisfy their differing requirements. Even in its smallest configuration, the z10 EC Model S64 system, which is the largest current model at this writing, provides at least 16 GB of memory and processes instructions at the rate of several billion instructions per second. In addition to the CPU, there are many large I/O devices— including tape drives and high-speed printers—and disks that store many billions or trillions of characters. The computer alone weighs over 5000 pounds/2200 kilograms!
Outsourced IT support The powerful z/OS operating system can keep track of hundreds or thousands of simultaneous users and divides the time among them to satisfy their differing requirements. Even in its smallest configuration, the z10 EC Model S64 system, which is the largest current model at this writing, provides at least 16 GB of memory and processes instructions at the rate of several billion instructions per second. In addition to the CPU, there are many large I/O devices
including tape drives and high-speed printers—and disks that store many billions or trillions of characters. The computer alone weighs over 5000 pounds/2200 kilograms!
outsourced IT support In contrast, the laptop PC shown in Figure 1.11 is designed for personal use. Everything is self-contained in one package. This system only has 2 GB of primary RAM storage and operates at a small fraction of the speed of the z10 EC. A hard drive is one of many storage options. The entire system, complete with display screen, built-in webcam, multiple network connections, and battery, weighs about three pounds (1.4 kilograms, if you prefer)
outsourced IT support Although these two systems seem very different, the difference is actually one of magnitude, not of concept. The large system operates much faster, can support much more memory, and handles more input and output much faster. It has operating system software that allows many users to share this larger resource. Nonetheless, the fundamental system architecture is remarkably similar in both cases. Even the actual processing performed by the CPU is similar
outsourced IT support In fact, today’s CPU operates in the same fundamental way as its CPU counterpart of fifty-five years ago, even though the construction is very different. Since computers all operate so similarly, regardless of size or type, it is not difficult today to transfer data between these different systems, allowing each system to do part of the processing for higher overall efficiency. This concept is known as distributed computing. The fact that different types of computers can work together, share files, and communicate successfully is known as open computing. Communication technology fulfills the requirements that make open and distributed computing possible. Computers are sometimes divided into categories: mainframe computers, minicomputers, workstations, and personal computers, but these categories are less significant than they once were. The capability of today’s personal computer far exceeds the capabilities of a mainframe computer of just a few years ago
outsourced IT support The Sun Ultra 40 computer is an example of a workstation that is frequently used as though it were a minicomputer, or even a small mainframe. Rather than attempting to categorize a particular computer, it is usually more productive to describe its capabilities in comparison to other systems being discussed or considered.