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**Digital Data Representation**

Class Handout

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**Digital Data Representation**

Data Representation Basics Representing Numbers, Text, and Pictures Quantifying Bits and Bytes Circuits and Chips

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**Digital=Distinct On / Off**

Data Representation Data representation refers to the form in which data is stored, processed, and transmitted. Digital devices work with distinct and separate data. Analog devices work with continuous data. Digitizing is the process of converting analog data into a digital format. Figure 1-23 Digital=Distinct On / Off Analog=Continuous

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**Representing Numbers, Characters (Text), Pictures, and Sound**

Numeric data Composed of numbers that might be used in arithmetic operations. Decimal number system has 10 symbols. Binary number system has only two symbols (0, 1). Character data Composed of letters, symbols, and numerals that are not used in arithmetic operations. ASCII, Extended ASCII, EBCDIC, and Unicode. Picture Data Composed of a series of dots. Each dot is assigned a binary number for color. Sound Data Is characterized by the properties of a sound wave. The wave can be represented digitally by sampling it a various points and converting those points into digital numbers. Figure 1-24

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**Memory Capacity Bit: Byte:**

Short for binary digit (0s and 1s), the only data that a CPU can process. Byte: An 8-bit string of data, needed to represent any one alphanumeric character or simple mathematical operation. In this picture, one byte, , represents the letter H Bit: Short for binary digit (0s and 1s), the only data that a CPU can process. Byte: An 8-bit string of data, needed to represent any one alphanumeric character or simple mathematical operation.

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**Numeric and Character Data Representation**

Figures 1-25 – 1-26

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**Hierarchy of Memory Capacity -Quantifying Bits and Bytes**

One binary digit Byte 8 bits Kilobyte (KB) Approximately one thousand bytes, (1024 or 210 bytes) Megabyte (MB) Approximately one million bytes (1,048,576 bytes, or 1,024 x 1,024 or 220 bytes). Gigabyte (GB) Actually 1,073,741,824 bytes (1,024 x 1,024 x 1,024 or 230 bytes). Terabyte One trillion bytes, or 240 bytes. Petabyte One thousand terabytes, or 250 bytes. Exabyte One thousand petabytes, or 260 bytes. Zettabyte One thousand exabytes. Kilobyte (KB): approximately one thousand bytes. Megabyte (MB): approximately one million bytes (1,048,576 bytes, or 1,024 x 1,024). Gigabyte (GB): actually 1,073,741,824 bytes (1,024 x 1,024 x 1,024 bytes). Terabyte: One trillion bytes. Petabyte: One thousand terabytes. Exabyte: One thousand petabytes. Zettabyte: one thousand exabytes.

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Circuits and Chips An integrated circuit (computer chip) is a super-thin slice of semiconducting material packed with microscopic circuit elements. DIP=Dual In-line Package PGA=Pin Grid Array Figures 1-30 and 1-31

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**How do bits and bytes fit together with chips and circuits?**

Bits take the form of electrical pulses that can travel over circuits. The 1 bit might represent an elevated voltage, such as 5 volts, whereas a 0 bit is represented by a low voltage, such as 0. The system board is a circuit board to which a multitude of electronic components are mounted. Motherboard Figure 1-32

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Digital Processing Programs and Instruction Sets Processor Logic

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**Programs and Instruction Sets**

Computers, portable media players, handheld computers, and smart phones all work with digital data. Computer programmers create programs that control digital devices. These programs are usually written in a high-level programming language. The human-readable version of a program created in a high-level language is called the source code.

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**Programs and Instruction Sets**

The procedure for translating source code into 0’s and 1’s can be accomplished by a compiler or an interpreter. Figures 1-34 – 1-35

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**Programs and Instruction Sets**

A collection of preprogrammed activities a microprocessor is hardwired to perform is called an instruction set. Additions, subtractions, counting, comparisons, etc Each instruction has a corresponding sequence of 0s and 1s might = Add. The list of codes for a microprocessor’s instruction set, called machine language, can be directly executed by the processor’s circuitry. This end product, the 1s and 0s, is called machine code.

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**Programs and Instruction Sets**

A machine code instruction has two parts. The op code and the operand. An op code (short for operation code) is a command word for an operation such as add, compare, or jump. The operand for an instruction specifies the data (or the address of the data) for the operation. Op Code Operand

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**Programs and Instruction Sets**

Many machine language instructions might be needed to equal a simple high-level program that counts to 100. Figure 1-36

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**Processor Logic-What happens inside a computer chip**

The arithmetic logic unit (ALU) is the part of the microprocessor that performs arithmetic operations. The ALU uses registers to hold data that is being processed. The microprocessor’s control unit fetches each instruction, just as you get each ingredient out of a cupboard or the refrigerator. The term instruction cycle refers to the process in which a computer executes a single instruction.

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**Processor Logic-What happens inside a computer chip**

Figures 1-37 – 1-38

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**Processor Logic-What role does the Control Unit play**

Figure 1-39

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