1、Basic Theory of Computer A computer is a tool for manipulating and storing information. Generally speaking, a computer is an electronic device that can accept input, process it according to a set of instructions, store the instructions and the results of processing, and produce results as its output
2、s. A computer system consists of hardware system and software system. The hardware system is usually divided into three major parts or primary subsystems: the CPU, the memory subsystem, and the IO subsystem. The CPU performs many operations and controls the computer. The memory subsystem is used to
3、store program being executed by the CPU， along with the programs data. The IO subsystem allows the CPU to interact with input and output devices, such as the keyboard and the monitor of a personal computer. This chapter will introduce the basic components of computer system. The basic components tha
4、t make up a computer system include: the CPU， memory, IO, and the bus that connects these components together. John Von Neuman, a pioneer in computer design, gave the architecture of most computers in use today. A typical John Von Neuman system has three major parts: the central processing unit( or
5、CPU )， memory, and input output (or IO). How a system designs these parts impacts the system performance. In VNA machines, like the 8086 family, the CPU is where all the actions take place. All computations occur inside the CPU. To the CPU, most IO devices look like memory because the CPU can store
6、data to an output device and read data form an input device. The major difference between memory and IO device is that IO device is generally associated the with the external devices in the outside world. The system bus connects various components of a VNA machine. The 8086 family has three major bu
7、ses: the address bus, the data bus, and the control bus. A bus is a connection of wires on which electrical signals pass through components in the system. For example, the data bus may have a different implementation between the 80386 and the 8086, but both carry data among the processor, IO, and me
8、mory. The 8086 processor uses the data bus to transfer data among the various components in a computer system. The size of this bus varies widely in the 8086 family. Indeed, this bus defines the size of the processor. The data bus on an 8086 family processor transfers information between a particula
9、r memory location or IO device and the CPU. The only question is, which memory location or IO device? The address bus answers this question. To differentiate memory location and IO device, a unique memory address is assigned to each memory element or each IO device. When the software wants to access
10、 certain memory location or IO device, it places the corresponding address on the address bus. Circuit associated with the memory or IO recognizes this address and instructs the memory or IO device to read the data from or place data on the data bus. The control bus is collection of signals that con
11、trols how the processor communicates with the rest of the system. Consider the data bus for a moment. The CPU sends data to memory and receives data from memory on the data bus. This prompts the question, Is it sending or receiving? There are two lines on the control bus, read line and write lines,
12、status lines, and so on. The exact structure of the control bus varies among processors in the 8086 family. However some control lines are common to all processors and are worthy a brief mention. The read line and the write line control the direction of data on the data bus. When both contain logic
13、1, the CPU, memory, and IO do not communicate with one another. If the read line is low, the CPU reads data form memory. If the write line is low, the system transfers data from the CPU to memory. The main memory is the central storage unit in a computer system. It is a relatively large and fast mem
14、ory used to store programs and data during the computer operation. The principal technology used for the main memory is based on the semiconductor integrated circuit. Integrated circuit RAM chip is available in two possible operation modes, static and dynamic. The static RAM consists essentially of
15、internal flip flops that store the binary information. The stored information remains valid as long as power is applied to the unit. The dynamic RAM stores the binary information in the form of electric charge that is applied to the capacitor. The capacitor is provided inside the chip by MOS transis
16、tor. The stored charge on the capacitor tends to discharge with the time and refreshing the dynamic memory can periodically recharge the capacitor. The dynamic RAM offers reduced power consumption and large storage capacity in a single memory chip. The static RAM is easier to use and has shorter rea
17、d or write cycles. Automation Automation, roboticization, or industrial automation or numerical control is the use of control systems such as computers to control industrial machinery and processes, reducing the need for human intervention. In the scope of industrialization, automation is a step bey
18、ond mechanization. Whereas mechanization provided human operators with machinery to assist them with the physical requirements of work, automation greatly reduces the need for human sensory and mental requirements as well. It is a great ideal of industries. After introducing automation, the quality
19、of the product is increased. The controlling logic and process methodology has been taken care by automation systems. Man is having tiredness, but for the automated instruments they can run continuously once they have been started. The instruments are very safe to human and environment by preventing
20、 hazards. Right now, man has become used to machines, but soon automation might replace man altogether and many people believe that is bad. Automation plays an increasingly important role in the global economy and in daily experience. Engineers strive to combine automated devices with mathematical a
21、nd organizational tools to create complex systems for a rapidly expanding range of applications and human activities. Many roles for humans in industrial processes presently lie beyond the scope of automation, Human-level pattern recognition language recognition, and language production ability are well beyond the capabilities of modern mechanical and computer systems. Tasks requiring subjective assessment or synthesis of complex
