Cad Guidebook: A Basic Manual for Understanding and Improving Computer-Aided Design by Stephen J. Schoonmaker Read Free Book Online Page B
Authors: Stephen J. Schoonmaker
essential elements of the system are the CPU, Memory, and Storage systems. However, there needs to be means by which the system is actually put into use and manipulated by programmers and users. This is accomplished by devices known as peripherals. The familiar devices that provide interactivity with the system are keyboards, monitors, pointing devices, speakers, etc. These types of devices will be discussed later in this chapter. One important peripheral for the basic functioning of a computer system is the Network Interface Card (NIC) or network card. This circuit board provides a connection between the computer system and a wider environment of computers and devices. This wider environ- ment is called a computer network or just a network.
Over the years, the relative importance of the computer network has steadily grown. At one time, a CAD-based computer would have been seen as a self-sufficient unit that occasionally communicated with other computers. How- ever, by the 1990s the network was seen as an essential element of any computer system, particularly since the mainframe ceased to be the foundation of a compu- tational framework. Instead, the foundation shifted to many smaller PCs and/or workstations. As that happened, the network was seen as the appropriate means to share resources. At first, this would be just for peripherals such as printers (an office with a dozen PCs could share one expensive printer). Then, the systems started to share data and storage. This meant that just one copy of a PC program could be loaded on a designated central computer system (instead of having to load the PC program to a dozen separate PCs).
24 Chapter 2
Although this new “file server” approach to networking sort of looks like the mainframe system again, there is a significant difference. With the mainframe computer, the data was indeed stored in a central storage system (similar to the “file server” of network), but all CPU power also had to come from that same mainframe computer. With the standard network approach, only the files came from the central storage, while the actual execution of the programs was still done “locally” (i.e. using the CPU in the user’s computer). The network approach means that the computational power demands of different users do not affect each other. So, if one user is running a CAD program that fully uses his CPU, it has no effect on other computer (CPUs) on the network that may not be running CAD programs. This would not be the case for the mainframe where all users are “competing” for the centralized CPU capabilities.
2.6.1 Local Area Network (LAN)
The kind of computer network that uses the central computer as the file server and/or the printer server is loosely referred to as a Local Area Network (LAN). The LAN was primarily a local network since the devices that connected to the network had very short distance requirements (such as no 2 computers could be more than 110 yards apart). However, over time, these restrictions became less and less severe, and LANs could grow to cover entire company sites and have 1000s or more computers and devices connected to the network. So, in general, most company-wide networks can just be considered LANs, and most commer- cial CAD systems in use are dependent on this type of network.
2.6.2 Wide Area Network (WAN)
Another class of network for connecting very wide spread sites (say at various locations in a country) is the Wide Area Network (WAN). At one time, this net- work would have used a entirely different type of hardware and software, but in many cases, the LAN type of approach can be adapted to the very long distances, but just with a vastly reduced performance. For instance, if phone lines are used to connect the different office sites, the speed at which the network data can be trans- mitted from one computer to another would be many times slower, but the user may see no difference in how the computer file is stored (it is
Over the years, the relative importance of the computer network has steadily grown. At one time, a CAD-based computer would have been seen as a self-sufficient unit that occasionally communicated with other computers. How- ever, by the 1990s the network was seen as an essential element of any computer system, particularly since the mainframe ceased to be the foundation of a compu- tational framework. Instead, the foundation shifted to many smaller PCs and/or workstations. As that happened, the network was seen as the appropriate means to share resources. At first, this would be just for peripherals such as printers (an office with a dozen PCs could share one expensive printer). Then, the systems started to share data and storage. This meant that just one copy of a PC program could be loaded on a designated central computer system (instead of having to load the PC program to a dozen separate PCs).
24 Chapter 2
Although this new “file server” approach to networking sort of looks like the mainframe system again, there is a significant difference. With the mainframe computer, the data was indeed stored in a central storage system (similar to the “file server” of network), but all CPU power also had to come from that same mainframe computer. With the standard network approach, only the files came from the central storage, while the actual execution of the programs was still done “locally” (i.e. using the CPU in the user’s computer). The network approach means that the computational power demands of different users do not affect each other. So, if one user is running a CAD program that fully uses his CPU, it has no effect on other computer (CPUs) on the network that may not be running CAD programs. This would not be the case for the mainframe where all users are “competing” for the centralized CPU capabilities.
2.6.1 Local Area Network (LAN)
The kind of computer network that uses the central computer as the file server and/or the printer server is loosely referred to as a Local Area Network (LAN). The LAN was primarily a local network since the devices that connected to the network had very short distance requirements (such as no 2 computers could be more than 110 yards apart). However, over time, these restrictions became less and less severe, and LANs could grow to cover entire company sites and have 1000s or more computers and devices connected to the network. So, in general, most company-wide networks can just be considered LANs, and most commer- cial CAD systems in use are dependent on this type of network.
2.6.2 Wide Area Network (WAN)
Another class of network for connecting very wide spread sites (say at various locations in a country) is the Wide Area Network (WAN). At one time, this net- work would have used a entirely different type of hardware and software, but in many cases, the LAN type of approach can be adapted to the very long distances, but just with a vastly reduced performance. For instance, if phone lines are used to connect the different office sites, the speed at which the network data can be trans- mitted from one computer to another would be many times slower, but the user may see no difference in how the computer file is stored (it is
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