Let us start with two basic definitions which may be obvious to most of you. Hardware refers to the physical computer, communication or control equipment. Software refers to the operating system and programs which run on the physical equipment.
Leibnitz conceptualized the concept of a computer in the 17th century. In the 19th century, Babbage made advances in mechanical computers. By World War II, warships had mechanical computers in the form of fire control systems. The first digital computer was built at Iowa State slightly before WWII. After World War II, the Americans built a digital computer using vacuum tubes for military ballistic studies. Like many post WWII technologies, computers were originally created for military purposes; however, the real advances did not materialize until they were applied to business problems thereby creating a large demand, which promoted advances through economic competition.
Advances in computers are made possible by advances in microelectronics. This is because (1) mechanical computers are far too large and too inaccurate, and (2) vacuum tube computers consume a great deal of power and break down frequently. What made the computer a commercial success was the invention of an inexpensive, reliable transistor, which required very little power. At first, transistors in computers were individually wired components. Technological advance led to boards with individual components, and finally to boards with integrated circuits. The advance in microelectronics has made the digital computer dominant over other types of computers because of its lower cost and higher performance.
The original computer developed by UNIVAC was funded by the military to solve problems such as the trajectories of shells. Sperry thought the demand was only about 4 to be used for trajectory studies and so did not push the marketing of computers. IBM saw the business possibilities of computers and developed its reputation not so much by product innovation, but by service and support. The computer market developed in the Fortune 500 companies and has progressively moved to smaller and smaller companies. Currently, the computer is entering the smallest of businesses. The computer is now even entering the home as a mass market item. The economics of the expansion are simple: as the market expands, the manufacturing costs fall which makes the computer a useful device to a larger and larger market and promotes further software development which in turn fuels the expansion by providing more application software to run on cheaper machines.
Today there is a vast array of different sized computers from small personal computers able to process hundreds of millions of instructions per second to giant supercomputers which can process trillions of instructions per second. A heuristic hierarchy might be personal computers, workstations, minicomputers, mainframes and supercomputers. In addition, special purpose computers act as control devices for numerous industrial activities such as chemical plants and communication exchanges. In new cars, a microprocessor controls the combustion process.
Because of Moore's Law concerning the increase in the number of electronic components on a chip, each new generation of computer is much more powerful than the last. When a new computer is designed, it is designed with an existing microprocessor. After six months to a year, the computer comes to market. To sell the computer the manufacturer makes sure that the computer is backwards compatible which means that it can run all the previous software for previous company machines. For example, 80486 personal computers can run all 80386 software, and likewise the Pentium chip was designed to run both 80486 and 80386 software. After several years the software industry catches up and creates software which explicitly uses the power of the new machine. For example, the new operating systems for the PC clone world are just now taking advantage of the power of the 80386 chip. In the meantime new PC machines have been developed on the next generation of microprocessor, Intel's Pentium, Pentium II and Pentium III series processors. Again there will be a lag of several years before software is developed which fully exploits the capabilities of the new machine.
Apple took a different approach to ensure backward compatibility between the 6800xx chips and the PowerPC RISC chip computers. Apple created a software emulator to run 6800xx software on the newer PowerPC computers. Usually emulators are too slow to be useful, but in Apple's case they were able to develop an efficient emulator.
Most computers today are the digital computers based on the Von Neumann design principle-(1) a single central processor; (2) a single path between the central processor and memory; (3) program is stored in memory; and (4) central processor fetches, decodes, and executes the stored instructions of the program sequentially. Almost all personal computers, workstations, minicomputers, and mainframes are currently Von Neumann design computers. To understand how such a computer works consider the following schematic drawing:
The various components of a computer are:
a. CPU: The central processor unit is the `brains' of a computer that contains the circuits that decode and execute instructions. Because of Moore's law, the number of integrated circuits necessary to create a CPU correspondingly decreased until, in 1975, the CPU for a personal computer could be designed on a single integrated circuit called a microprocessor. Since that time, each generation of microprocessors is more powerful than the last. Two types of microprocessors are CISC and RISC. Simply put, the instructions for the first type are much more complex than for the latter. Examples of CISC are the Intel 80x86 and Motorola 680x0 series microprocessors. Apple switched to RISC with the introduction of the PowerPC. To do this they had to create an emulator to run previous software. However, Intel is incorporating most of the features of RISC chips in the next generations of its CISC chips. RISC chips are more powerful and are found in workstations such as those from SUN. Besides a single CPU, a Von Neumann design might have several coprocessors-that are subordinates processors for arithmetic and fast video displays. The latest advance is to put to cores (processors) on a single microprocessor chip.
CPU
b. Memory Pyramid : As CPUs have become faster and more powerful, a fundamental bottleneck in computer design is the flow of information back and forth from memory to the CPU. As computing of videos becomes more important, the need to move large amounts of data quickly from storage to the CPU grows accordingly.
Currently, there are now many types of memory devices with different costs, access times and storage capacities. Generally the faster the access time, the more expensive the memory. Consequently, good design is based on a memory pyramid for providing increasing amounts of less costly, slower memory.
(1) Cache memory: This generally is memory placed on the CPU or is attached with a special fast bus. It is the fastest and most expensive, so little is used.
(2). RAM(DRAM and SRAM) and ROM: These are various types of memory chips directly accessible to the computer. The two most important types of random access memory, RAM, are dynamic(DRAM) and static(SRAM). The advantage of the latter is that memory is retained when you turn off the computer. Read only memory, ROM, is a special type of memory for reading but not writing. This type of memory is useful for storing frequently used software, for which the user needs rapid access but has no need to modify. Memory chips are more expensive and faster than the various types of magnetic and laser disk memories.
As the cost of a bit of integrated circuit storage has been decreasing by about 30-35%each year, it is not surprising that each new generation of computers has much greater RAM storage than the previous generation. For example, the APPLE II had 48K and was expandable to 64K; the MAC started at 128K and now is rarely purchased with less the 64M of RAM. (K stands for one thousand and M stands for one million.). Similarly, a buyer would currently purchase a PC with as much as 128M of memory.
(3). Magnetic Disk: These are magnetic disks of various types, such as floppies (5 1/4 and 3 1/2) and hard disk. These devices are cheaper and can store much greater amounts of data than RAMs, but have slower access time, which is the amount of time it takes the computer to read information from the magnetic disk into RAM. Over time technological advances make it possible to store increasing amounts of information per square inch of disk space. For example, firms are now selling floppy 3 1/2" disk drives with a capacity of 100M per diskette. Generally a computer has a much bigger hard disk memory than the memory on integrated circuits. Also, over time computers have increasing amounts of magnetic disk space. The advances in magnetic disk in terms of capacity and cost is analogous to Moore's Law
(4). Bubble memory: This is an expensive, magnetic type of memory device which currently has not achieved its potential. Bubble memory has the potential to store the information contained in the Library of Congress on a device the size of a 1/4 inch cube. This type of memory has some applications in portable computers.
(5). Laser Disk: A new type of memory device is the laser disk that can store very large amounts of data. This type of memory device is beginning to be used in library applications. Cheaper, but much slower than hard disks, CD-ROM refers to read only laser disks. With the advance of laser dish technology CD-ROM technology is now being replaced with DVD technology. DVD disks are the same size as CD-ROM disks so that a DVD player can play CD-ROMs. The advantage of DVD technology is the increased storage capacity so that DVDs can plan a feature length movie. DVDs will probably gradually replace VHS tapes like the ones rented from BlockBuster. There is a battle over standards for DVDs that may not be resolved until 2007 or so.
Laser Disk
(6). Holograph memory: This is a new type of memory based on holograph patterns which is just now entering the market. The commercial potential for this type of memory device is very large because it is fast and can store a prodigious amount of information. Thus, this type of memory will be very useful in multimedia computers because the processing power of microprocessors has advanced much faster than the ability to move large amounts of data required for dynamic images from memory to the CPU.
Holographic Memory
c. Input/Output Devices
Keyboard, mouse and video screen
Printers: Dot matrix impact, Inkjet and Laser
Modem to phone: You can connect your computer to a network over analoy phone with an effective capacity of about 40K bits/sec, over an DSL line with a capacity of 1.5M bits/ second or cable modem that is higher than DSL. US capacity is way behind over countries such as Japan where connection speed is about 20M bits/second.
Currently a great R&D effort is being made on pen input devices which can read handwriting, such as the Palm Pilot. This is a problem in pattern recognition. Also, voice input devices are now becoming a part of PCs. Again, this is a serious problem in pattern recognition.
Handwriting recognition software
d. Bus: The bus is the electric circuit connecting the components of the computer together. The more powerful the computer, the bigger the bus, where bus size refers to the number of bits which can be communicated at one time. The trend in personal computers has moved from 8 to 16 to 32 and is moving to 64 bits buses currently. As we move towards multimedia, the need to move large blocks of data very quickly will increase.
e. Clock: The clock synchronizes the components of a computer to work together. A faster clock enables the computer to execute more instructions a second. Since the 1970s, clocks on personal computers have increased from 1 to over 400 million cycles a second. The faster the clock the more heat is generated and the more steps must be taken to keep the electronic devices cool. Personal computers currently have two clocks: one for the CPU and one for the bus with the CPU clock running up to 10 times faster than the bus clock. The bus clock speed must be increased as we move into processing dynamic images.
Von Neumann
Originally corporations had standalone computers which were fed input from cards and magnetic tapes. Early evolution was towards more powerful mainframes. The next step were systems of terminals connected to the corporate mainframe. The UT business school once had such a system.
The mainframe, generally IBM, with up to hundreds of dumb terminals was a big advance in that instead of having to submit cards to the mainframe each computer user could manage his or her jobs using keyboard input. Since the mainframe was a sequential computer it did not process all the input from the users simultaneously, but rather proceeded to devote a small time slot of the central processor resources to each job in sequence. The downside of this approach was that the operating system of the mainframe spent a considerable overhead in shifting from one job to another.