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Chapter 4,8,9,11

ITEC 1000 Chapter Notes - Chapter 4,8,9,11: Front-Side Bus, Wordperfect, Superscalar Processor

Information Technology
Course Code
ITEC 1000

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Chapter 4 Data Forms
For storage and transmission of data, a representation different from that used
for internal processing is often necessary. In addition to the actual data
representing points in an image or characters being displayed, the system must
store and pass along information that describes or interprets the meaning of the
data. Such information is known as metadata. In some cases, the description is
simple: to read a pure text file may require only a single piece of information that
indicates the number of characters in the text or marks the end of the text. A
graphic image or sound requires a much more detailed description of the data.
To reproduce the image, a system must know the type of graphical image, the
number of colors represented by each data point, the method used to represent
each color, the number of horizontal and vertical data points, the order in which
data points are stored, the relative scaling of each axis, the location of the image
on the screen, and much more.
Individual programs can store and process data in any format that they want. The
format used to process and store text in WordPerfect is different from that used
by Microsoft Word, for example. The formats used by individual programs are
known as proprietary formats. Proprietary formats are often suitable for an
individual user or a group of users working on similar computer systems. As
noted in Chapter 1, proprietary standards sometimes become de facto standards
due to general user acceptance.
Three alphanumeric codes are in common use. The three codes are known as
Unicode, ASCII (which stands for American Standard Code for Information
Interchange, pronounced ‘‘as-key’’ with a soft ‘‘s’’), and EBCDIC (Extended
Binary Coded Decimal Interchange Code, pronounced ‘‘ebb-see-dick’’). EBCDIC
was developed by IBM. Its use is restricted mostly to older IBM and IBM-
compatible maniframe computers and terminals. The Web makes EBCDIC
particularly unsuitable for current work. Nearly everyone today uses Unicode or
ASCII. Still, it will be many years before EBCDIC totally disappears from the
Keyboard Input: Most alphanumeric data in the computer results from keyboard
input, although alternative forms of data input can be used. Operation of a
keyboard is quite simple and straightforward: when a key is struck on the

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keyboard, the circuitry in the keyboard generates a binary code, called a scan
code. When the key is released, a different scan code is generated. There are
two different scan codes for every key on the keyboard. The scan codes are
converted to the appropriate Unicode, ASCII, or EBCDIC codes by software
within the terminal or personal computer to which the keyboard is connected.
The use of separate scan codes for key press and release functions allows the
system to detect and process multiple key combinations, such as those used by
the shift and control keys.
Chapter 8
This performs arithmetic and logic operations.
ALU - Can add, subtract, multiple, divide.
Logic: AND, OR, NOT etc. - Holds data temporarily
This performs the fetch/execute cycle.
CU (Control Unit) - Accesses/retrieves instructions from memory - Issues
commands to ALU - Moves data to/from CPU registers/hardware - Doesn't
change the data.
Program counter (instruction pointer) contains: The address of the current or next
Memory management unit supervises the fetching of instructions and data from

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Where are registers wired? Within the CPU directly. So there is no addresses
Registers are sized in bits/bytes/mb/gb? Bits and bytes only. Not MB like
What 3 things can a register hold? Data, an address, or an instruction.
5 Functions of Registers: 1. Hold Data being processed 2. Hold Instruction
being executed 3. Contain Memory/IO Address being accessed 4. Keep status of
computer. 5. Conditional branch instructions
General-Purpose Registers hold data of arithmetic operations. They hold
intermediate data values. They also transfer data between memory locations and
between IO and memory.
Accumulators are General Purpose Registers in the CPU used for the actual
manipulation of data. Usually contain results of arithmetic or logical operations.
While General-Purpose Registers are part of the ALU. Special-Purpose
Registers are part of the CU. The main 5 SPRs are: 1. Program Counter (PC)
(instruction pointer). Holds address of currently executed instruction. 2.
Instruction Register (IR). Holds the actual instruction being executed. 3. Memory
Address Register (MAR). Holds the address of a memory location. 4. Memory
Data Register (MDR). Holds the actual data values from location specified in
MAR. 5. Flags = (one-bit). Special conditions = errors, failures. Status registers
are several flags together.
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