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Text B: Data Processing Means

The CPU and memory – are both housed together in the same box, called the system unit. All other computer system devices are linked into the system unit housing. The execution of any machine-level instruction involves two phases: the instruction phase and the execution phase. The results are stored in registers or memory. After both phases have been completed for one instruction, they are again performed for the second instruction, and so on. The instruction phase followed by the execution phase is called a machine cycle. Machine cycle times are measured in microseconds or in terms of how many instructions are executed in a second. Today’s central processing units speed up processing by using pipelining, when the CPU gets one instruction, decodes another, and executes a third at the same time.

Data is moved within a computer system in a group of bits. A bit (b) is a binary digit– 0 or 1. The processing speed is the number of bits the CPU can process at any one time. This number of bits is called the word length of the CPU. The larger word length increases the speed of processing. Each CPU produces a series of electronic pulses at a predetermined rate, called the clock speed, which affects machine cycle time. Clock speed is often measured in megahertz (where one hertz means one cycle or pulse per second).

Data is transferred from the CPU to other system components via bus lines the physical wiring that connects the computer system components. The number of bites a bus line can transfer any time is known as bus line width. Bus line width should be matched with CPU word length for optimal system performance. The larger is word length, the more powerful is the computer. Most CPUs are collections of digital circuits imprinted on silicon wafers, or chips. Reducing the distance between the points of destination on chips increases the speed of processing. Chips built from less resistant superconductive metals also increase processing speed.

Mark the following statements as true or false.

1. The system unit holds the CPU and I/O devices. 2. The instruction phase and the execution phase of a machine instruction are performed simultaneously. 3. The CPU performance is decreased by using pipelining. 4. Transferring data from the CPU to other system components involves using bus lines.

5. The word length of the CPU affects the computer performance.

Put the letters in the following words into the correct order.

a) aefnrrst; b)eeiilnpp; c) deghlnortw; d)acefft; e) acemopr;

f) tciriuc; g) cudcteinoprsuve

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