CHAP. 3] COMPUTER ORGANIZATION 35
36 COMPUTER ORGANIZATION [CHAP. 3
If the program expects to find a character, it will try to interpret the bits as a character. If the bit pattern
doesn??™t make sense as a character encoding, either the program will fail or an error message will result.
Likewise, if the program expects an integer, it will interpret the bit pattern as an integer, even if the bit pattern
originally encoded a character. It is incumbent on the programmer to be sure that the program??™s handling of data
is appropriate.
CPU/ALU
The CPU is the part of the computer one thinks of first when describing the components of a computer. The
repetitive cycle of the von Neumann computer is to a) load an instruction from memory into the CPU, and b)
decode and execute the instruction. Executing the instruction may include performing arithmetic or logical
operations, and also loading or storing data in memory. When the instruction execution is complete, the computer
fetches the next instruction from memory, and executes that instruction. The cycle continues indefinitely,
unless the instruction fetched turns out to be a HALT instruction.
The CPU is usually described as consisting of a control unit and an arithmetic and logic unit (ALU).
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