11-05-2012, 10:39 AM
Hardware, Input, Processing, and Output Devices
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Hardware
Any machinery (most of which uses digital circuits) that assists in the input, processing, storage, and output activities of an information system
Hardware Components
Central processing unit (CPU)
A hardware component that performs computing functions utilizing the ALU, control unit, and registers.
Arithmetic/logic unit (ALU)
Performs mathematical calculations and makes logical comparisons
Control unit
Sequentially accesses program instructions, decodes them, coordinates flow of data in/out of ALU, registers, primary and secondary storage, and various output devices
Execution of an Instruction
Machine cycle
Instruction phase
Execution phase
Instruction phase
Step 1: Fetch instruction
Step 2: Decode instruction
Execute phase
Step 3: Execute instruction
Step 4: Store results
Machine Cycle Time
Machine cycle time
Time it takes to execute an instruction
Slow machines
Measured in microseconds (one-millionth of a second)
Fast machines
Measured in nanoseconds (one-billionth of a second) to picoseconds (one-trillionth of a second)
MIPS
Millions of instructions per second