2020-10-11
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If you are "tuned in" to the amount of processing power in your computer, you won't fall into the trap that many people do. We mean that of buying a software program that won't run on your computer, or expecting the computer to do something it isn't capable of doing. The most important processing hardware component is the central processing unit (CPU), which comprises the control unit and the arithmetic/logic unit ( ALU). CPUs used to be made of vacuum tubes, magnetic cores, and transistors, which were all relatively expensive, slow, and unreliable by today's standards. Today CPUs are manufactured from silicon; one wafer from a silicon ingot can hold hundreds of chips, called microprocessors. The electric circuitry that forms the CPU is etched onto the surface of the chip.
The control unit of the CPU is responsible for directing and coordinating most of the computer system activities. It uses machine language to run the show.
Unfortunately, the binary codes that make up machine language differ among machines, which creates a problem of incompatibility.
The arithmetic/logic unit (ALU) performs all arithmetic and logical (comparison) functions (plus, minus, times, divide by, equal to, less than, greater than, not equal to).
Registers are special temporary storage locations within the CPU that very quickly accept, store, and transfer data and instructions that are being used immediately. The number and types of registers in a computer vary according to the computer's design.
To get data and instructions moving among the various components of the system, the computer needs buses. The wider the bus, the more data it can carry at one time.
The cycle that the computer goes through to fetch and execute one instruction is called the machine cycle. In the instruction cycle part of the machine cycle, an instruction is retrieved from main memory and is decoded in the CPU. The time it takes to do this is called I-time. In the execution cycle, the instruction is executed and the result is stored. The time this takes is E-time. An internal clock in the CPU sets the speed of the machine cycle, which is measured in MHz—megahertz, or millions of cycles per second.
A computer system could not operate without main memory, also called internal memory, primary memory, primary storage, random access memory (RAM), or simply memory. In general, main memory is used to store a copy of the main software program that controls the general operation of the computer; to store a copy of the business application software you are using; to temporarily store data that has been input from the keyboard or other storage device until it is ready for processing; and to temporarily store data that has been produced as a result of processing until it is ready for output or secondary storage. In a microcomputer, main memory, or RAM, chips are usually found in banks of nine on the motherboard. A character's 8 bits are stored in a row of chips; the ninth chip holds the parity bit, which is a 1 or a 0 based on whether the parity scheme is odd or even. The parity scheme is used to check for errors produced by interferences with the electrical current.
If you have a microcomputer that needs to have its RAM expanded beyond 640 K to handle new types of software, you can purchase an add-on board, also called an expanded memory board, to "plug in" to the motherboard.
In general, a ROM chip stores instructions necessary to tell a computer what to do when it is first turned on. These instructions are installed by the manufacturer and generally cannot be changed by the user.
Certain types of ROM chips give users added flexibility. Programmable read-only memory (PROM) chips allow you to put your own data and programs on them. Erasable programmable read-only memory (EPROM) chips can be changed by using a special ultraviolet light device; however, you have to take EPROM chips out of the computer to change the data and programs on them. Electrically erasable programmable read-only memory (EEPROM) chips can be changed without taking them out of the computer.
The processing power of a computer can be determined using the following factors: (1) addressing scheme, (2) register size, (3) data bus, (4) clock speed, and (5) the instruction set.
IV. Comprehension Check.
1. Match the following words with their synonyms marked in the text with bold type: keeps, depending upon, to retrieve, cells, purchasing, builds up, receive, costly, in accordance with, move, for some time.
2. Match each of the following terms to the phrase that is the most closely related:
1.machine language, 2. central processing unit, 3. machine cycle, 4.RAM, 5.open
architecture, 6. main memory, 7. arithmetic/logic unit, 8. add-on memory board
9. ROM, 10. microprocessor, 11. register, 12. clock speed, 13. semiconductor,
14. control uni, 15.bus
a. The only language that the CPU can understand
b. If a computer was designed using this approach, you can upgrade it with more RAM and add graphics and communications capabilities.
c. Read-only memory
d. Electronic pathway
e. Temporary storage location within the CPU
f. Random access memory
g. The "brain" of the computer
h. Instruction cycle and execution cycle together
i. Hardware component responsible for directing and coordinating most of the computer system activities
j. Storage area outside the CPU where data and instructions needed by the CPU are held temporarily
k. Material used in chips to form electric circuits
l. CPU circuitry of a microcomputer
m. Refers to the speed with which a computer performs operations
n. Technology developed so microcomputers could use more than 640 K main memory
o. Hardware component of the CPU that performs mathematical calculations and logical comparisons
