Basic Computer Basic Computer OrganizationOrganization

Rashedul Hasan.Rashedul Hasan.

Five basic operationFive basic operation

No matter what shape, size, cost No matter what shape, size, cost and speed of computer we are and speed of computer we are talking about, all computer systems talking about, all computer systems perform the basic 5 operations for perform the basic 5 operations for converting raw input data into useful converting raw input data into useful information and presenting it to a information and presenting it to a user. user.

Five basic operationFive basic operation

Inputting: is the process of entering data Inputting: is the process of entering data and instructions into computer system.and instructions into computer system.

Storing: is the process of saving data and Storing: is the process of saving data and instructions to make them available instructions to make them available whenever they are required.whenever they are required.

Processing: involves in the performing Processing: involves in the performing arithmetic operations (add, subtract, arithmetic operations (add, subtract, multiply, divide etc.) or logical operation multiply, divide etc.) or logical operation (comparison like equal to, less than, greater (comparison like equal to, less than, greater than etc.) on data to convert them than etc.) on data to convert them

Five basic operationFive basic operation

Into useful information. Into useful information. Outputting: process of producing Outputting: process of producing

useful information or results for user, useful information or results for user, such as printed report or visual such as printed report or visual display. display.

Controlling: directing the manner and Controlling: directing the manner and sequence in which the above sequence in which the above operations are performed. operations are performed.

CPUCPU

In put Unit In put Unit

Data and instruction must enter a Data and instruction must enter a computer before the computer can computer before the computer can perform any operation. The input unit perform any operation. The input unit that links a computer with its that links a computer with its external environment performs this external environment performs this task. Data and instructions enter a task. Data and instructions enter a computer through an input unit in a computer through an input unit in a form that depends upon the input form that depends upon the input device used. device used.

In put UnitIn put Unit

For example, data can be entered using For example, data can be entered using keyboard in a manner similar to typing, keyboard in a manner similar to typing, and this differs from the way in which and this differs from the way in which data is entered through a Scanner. data is entered through a Scanner.

But computer’s memory is designed to But computer’s memory is designed to accept input in binary code and hence, accept input in binary code and hence, all input devices must transform input all input devices must transform input signals to binary code. signals to binary code.

In put UnitIn put Unit

In short, an input unit performs following In short, an input unit performs following functions,functions,

1.1. It accepts instructions and data from It accepts instructions and data from outside world.outside world.

2.2. It converts data and instructions in It converts data and instructions in computer acceptable form.computer acceptable form.

3.3. It supplies the converted instructions and It supplies the converted instructions and data to computer system for further data to computer system for further processing. processing.

Out Put UnitOut Put Unit

An output unit perform the opposite An output unit perform the opposite functions of the input unit. It supplies functions of the input unit. It supplies information to outside world. Hence, it information to outside world. Hence, it links a computer with its external links a computer with its external environment. As computer works with environment. As computer works with binary code, result produces are also in binary code, result produces are also in binary form. Therefore, before binary form. Therefore, before supplying the results the system must supplying the results the system must convert them to human acceptable convert them to human acceptable form. form.

Out Put UnitOut Put Unit

In short, an output unit performs In short, an output unit performs following functions,following functions,

1.1. It accepts the results produced by a It accepts the results produced by a computer in a coded form.computer in a coded form.

2.2. It converts these coded results to It converts these coded results to human acceptable (readable) form.human acceptable (readable) form.

3.3. It supplies the converted results to It supplies the converted results to outside world.outside world.

Storage UnitStorage Unit

Data and instructions entered into a Data and instructions entered into a computer system through input units computer system through input units have to be stored inside the have to be stored inside the computer before actual processing computer before actual processing starts. Similarly results produced by starts. Similarly results produced by a computer after processing have to a computer after processing have to be kept inside the computer before be kept inside the computer before being passed on to an output unit. being passed on to an output unit. Storage unit usually do these things. Storage unit usually do these things.

Storage UnitStorage Unit

In short, storage units holds,In short, storage units holds,

1.1. Data and instructions required for Data and instructions required for processing.processing.

2.2. Intermediate results of processing.Intermediate results of processing.

3.3. Results for output, before they are Results for output, before they are released to an output device. released to an output device.

Memory Memory

A computer's memory can be viewed as a A computer's memory can be viewed as a list of cells into which numbers can be list of cells into which numbers can be placed or read. placed or read.

Each cell has a numbered "address" and Each cell has a numbered "address" and can store a single number. can store a single number.

The computer can be instructed to "put The computer can be instructed to "put the number 123 into the cell numbered the number 123 into the cell numbered 1357" or to "add the number that is in cell 1357" or to "add the number that is in cell 1357 to the number that is in cell 2468 1357 to the number that is in cell 2468 and put the answer into cell 1595".and put the answer into cell 1595".

Main components of storage Main components of storage unitunit

Primary StoragePrimary Storage

Secondary StorageSecondary Storage

Primary StoragePrimary Storage

It also known as Main memory. It is It also known as Main memory. It is used to hold: used to hold:

pieces of program instructions pieces of program instructions and data,and data,

intermediate results of intermediate results of processing,processing,

recently produced results of those recently produced results of those jobs jobs on which the computer is on which the computer is currently currently working. working.

Primary StoragePrimary Storage

CPU can access main memory at a CPU can access main memory at a high speed. high speed.

But primary storage can hold But primary storage can hold information only while computer information only while computer system is on. As soon as the system is on. As soon as the computer turn off, the information computer turn off, the information held in primary storage is erased. held in primary storage is erased.

It has limited storage capacity. It has limited storage capacity. It is very expensive. It is very expensive.

Secondary StorageSecondary Storage

It is also known auxiliary storage. It is also known auxiliary storage.

It is much cheaper than primary It is much cheaper than primary storage and it can retain information storage and it can retain information even when a computer switches off. even when a computer switches off.

Central Processing UnitCentral Processing Unit

Control unit [CU] and Arithmetic Logic Control unit [CU] and Arithmetic Logic unit [ALU] of a computer system are unit [ALU] of a computer system are together known as Central processing together known as Central processing unit [CPU]. unit [CPU].

The CPU is the brain of a computer.The CPU is the brain of a computer.All major calculation and comparisons All major calculation and comparisons

take place inside the CPU and the CPU take place inside the CPU and the CPU is responsible for activating and is responsible for activating and controlling the operations of other controlling the operations of other units of Computer. units of Computer.

Control unitControl unit

How does an input device know that it is How does an input device know that it is time for it to feed data to storage unit? How time for it to feed data to storage unit? How does the ALU know what should be done does the ALU know what should be done with the data once they are received?with the data once they are received?How it is that only result for output are sent How it is that only result for output are sent to an output device and not the to an output device and not the intermediate result?intermediate result?

All of this possible due to control unit. All of this possible due to control unit. Although it does not perform any actual Although it does not perform any actual processing on data.processing on data.It manages and coordinates the entire It manages and coordinates the entire computer system. computer system.

Control unitControl unit

It obtains instructions from the It obtains instructions from the program stored in main memory, program stored in main memory, interprets the instructions and issues interprets the instructions and issues signals causing other units of the signals causing other units of the system to execute them. system to execute them.

Arithmetic Logic UnitArithmetic Logic Unit

The ALU is capable of performing two The ALU is capable of performing two classes of operations: arithmetic and classes of operations: arithmetic and logic.logic.Arithmetic operations: addition, subtraction, Arithmetic operations: addition, subtraction,

multiplication and division.multiplication and division.Logical operations compare numbers, letters Logical operations compare numbers, letters

and special characters, AND, OR and NOT.and special characters, AND, OR and NOT.Comparison operations test for three Comparison operations test for three

conditions, =, <, >conditions, =, <, >

If A = BIf A = B If B = CIf B = CThen A = C is it a correct statement.Then A = C is it a correct statement.

The Computer’s Core:The Computer’s Core:The CPU and MemoryThe CPU and Memory

The transformations The transformations are performed by the are performed by the CPU - the CPU - the central central processing unitprocessing unit or or processor.processor.

The microprocessor, The microprocessor, which is a silicon which is a silicon chip, is located on chip, is located on the the motherboard.motherboard.

~55 milliontransistors

Bit:Bit: Short for binary digit (0s and 1s), the Short for binary digit (0s and 1s), the only data that a CPU can process. only data that a CPU can process.

Byte: Byte: An 8-bit string of data, needed to An 8-bit string of data, needed to represent any one alphanumeric represent any one alphanumeric character or simple mathematical character or simple mathematical operation.operation.

8 bit = 1 Byte.8 bit = 1 Byte.

Kilobyte (KB): approximately one thousand Kilobyte (KB): approximately one thousand bytes.bytes.Megabyte (MB): approximately one million Megabyte (MB): approximately one million bytes (1,048,576 bytes, or 1,024 x 1,024).bytes (1,048,576 bytes, or 1,024 x 1,024).Gigabyte (GB): actually 1,073,741,824 bytes Gigabyte (GB): actually 1,073,741,824 bytes (1,024 x 1,024 x 1,024 bytes)(1,024 x 1,024 x 1,024 bytes)Terabyte: One trillion bytesTerabyte: One trillion bytesPetabyte: Approximately 10Petabyte: Approximately 101515 bytes. bytes.Exabyte: Approximately 10Exabyte: Approximately 101818 bytes. bytes.

Memory CapacityMemory Capacity