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Wednesday, April 19, 2023
Slide 1
Low Level Machine
Wednesday, April 19, 2023
Slide 2
Low Level Machine
Bit A bit is a Binary Digit, either a 0 or a 1.
Byte A group of eight bits is called a byte.
Kilobyte (Kb) One Kilobyte = 1024 bytes210 =1024 (2x2x2x2x2x2x2x2x2x2 = 1024)
Megabyte (Mb) One Megabyte = 1024 Kbytes
Gigabyte (Gb) One Gigabyte = 1024 Mbytes
Terabyte (Tb) One Terabyte = 1024 Gbytes
Wednesday, April 19, 2023
Slide 3
Stored Program
An organized list of instructions that tell the computer how to carry out tasks.
Without programs, computers are useless.
Every program must be translated into a code that the computer can understand. This is performed by Translator Programs.
The code produced is called Machine Code (the computers own language) and consists of binary digits 0 and 1.
Wednesday, April 19, 2023
Slide 4
Input - Process - Output
Most jobs that you do can be split up into three main stages: input - process - output.
What are the main stages in washing the dishes?
To complete any task a computer needs data and instructions as - INPUT
The processor carries out the instructions and produces a result. - PROCESS
This result can be displayed on a monitor, saved or printed - OUTPUT
Wednesday, April 19, 2023
Slide 5
Diagram of Processor and Main Memory
Input Devices
Main Memory
Output Devices
CPU
Backing Storage Devices
Wednesday, April 19, 2023
Slide 6
Representing Text
All the characters that a user enters using the keyboard need to be stored using 1s and 0s. Each character is given a special code.
One of the most popular ways is to use:ASCII (pronounced askee)
Each letter, number and symbol is given a code from 0 to 127.
For example M is 77 and m is 109.
Most computer use ASCII code which makes it possible to transfer data from one computer to another easily.
Wednesday, April 19, 2023
Slide 7
Character SetA list of all the characters stored by the computer and represented by ASCII.
Control CharactersIn addition to characters the ASCII code also represents control characters (0 to 31). They do not appear on the monitor or printouts because they are not data but control operating functions. Example: 7 = makes a beep12 = clears the screen
Wednesday, April 19, 2023
Slide 8
Representing Graphics
Pictures on a computer screen are made up from tiny dots called pixels. Imagine the whole of the computer screen being made up of thousands of pixels.
In a B/W monitor each pixel may be on (black) or off (white) depending on whether the value of the pixel in memory is 1 (on) or 0 (off).
Resolution of GraphicsThis is a measure of the number of pixels used to store a picture.
High resolution means smaller pixels and more of them.
Low resolution means larger pixels and less of them.
Wednesday, April 19, 2023
Slide 9
Black & White Graphics Calculations
To store this graphic we would need8 x 8 = 64 pixels
Each pixel needs 1 bit of storage.=64 bits=64/8 = 8 bytes
To store this graphic we would need 16 x 16 = 256 pixels
Each pixel needs 1 bit of storage.=256 bits=256/8 = 32 bytes
Low Resolution
Higher Resolution
Wednesday, April 19, 2023
Slide 10
Central Processing Unit (CPU)
The CPU has three main parts:
1.Control UnitFetches instructions from memory.Decodes instructions.Carries out the instruction.
2.Arithmetic & Logic Unit (ALU)The ALU carries out all the computer’s arithmetic and logical functions.• Arithmetic functions: + - x /• Logical functions such as comparing values.
3.Main MemoryThe main memory is used to hold the programs data being used. Another term for main memory is RAM.
Wednesday, April 19, 2023
Slide 11
RegistersSpecial, high-speed storage areas within the CPU. All data must be represented in a register before it can be processed.
E.g. if two numbers are to be multiplied, both numbers must be in registers, and the result is also placed in a register.
The number of registers that a CPU has and the size of each determine the power and speed of a CPU.
Wednesday, April 19, 2023
Slide 12
Word
A word, in computing, is a collection of bits treated as a single unit by the processor.
In practice, this refers to the number of bits moved as a group, either as an instruction or as data.
Example: 8 bits, 16 bits, 32 bits or 64 bits.
The larger the word size=the more data that can be moved in one go=the more powerful the processor.
Main Memory
CPU
Wednesday, April 19, 2023
Slide 13
Addressability
The place where each item is stored in a computer’s memory is important because the computer has to be able to find any given item of data. An item is stored in memory in a storage location.
Each storage location has a unique address in the same way you have a unique home address.