Transcript Chapter 1 (MIS by Oz and Jones)

Chapter 4: Business Hardware
and Software
Introduction:
Working of the computer.
Page 139 - 142
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Two Types of Computers:
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Analog:
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Example:
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Measures, by representing numerical information
by means of voltages proportional in magnitude
to the numbers involved, and like any measuring
device, has a built-in error of measurement.
If the number 3 is represented by 0.16 Volts,
And 16 is 0.3 V,
Then the product can be 0.485 V, or 0.478 V and
ONLY by chance it will be 0.48 V
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Digital Computer:
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This computer COUNTS!
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In applications where approximate results
are acceptable, the analog computer is
widely used. BUT not in business
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And would calculate the product of 16 and 3 as
EXACTLY 48
The customer balance is about R 100-00
Its either R100-00, or R100-01!!
Structure of a computer system:
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It has NO magical image!!
Remember a computer only does what it is
told to do by a set of instructions, called a
program.
A computer system:
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Input
Output
CPU
Internal memory and ‘Storage/External Memory’
Input/Output
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For a computer to function it must have
information. It is the user’s responsibility to
accumulate the data, CHECKING it,
validating it and then entered it into the
computer
Output: is the result of processing and can be
video, printed or output to your monitor
screen
Memory:
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Information is processed internally in the
computer’s memory
Data are READ into the memory and the
results are READ OUT (written) from memory
Processing is done according to a set of
instructions that is also stored in the memory
Conclusion: whatever goes into a computer or
comes out of a computer must pass through
memory
CPU:
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Google a picture of the CPU
CPU:
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With all their sophistication, most computers still function
as they were designed to work almost 60 years ago:
A single CPU performs four basic steps:
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fetch (an instruction), decode, execute, and store.
Basically, the only change to this concept
(proposed by John von Neumann in the early 1940s) is
multiprocessing: more than one CPU in a computer!
Task: Identify these processes on the next slide!
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Digits:
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Characters are written to memory in terms of
two binary digits: 0 and 1 (bits)
ON is 1 and OFF is 0
In the next slide assume that each memory
location (address) consists of 8 switches or
transistors forming a ‘word’. 8 bits is called a
BYTE
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Binary Code Deciphering:
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First character is: 0 1 0 0 0 1 1 1
Giving us:
Second character is: 0 0 1 1 1 0 0 1
Giving us:
Hint: Use Google and search for ASCII code
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Memory:
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On command, the CPU can switch
characters about, modify them, or even
erase them entirely, by simply switching the
transistors from ON to OFF or vice versa
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