Basic Computer Organization

1. Basic Computer Organization Rashedul Hasan.

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

4. Five basic operation • Inputting: is the process of entering data and instructions into computer system. • Storing: is the process of saving data and instructions to make them available whenever they are required. • Processing: involves in the performing arithmetic operations (add, subtract, multiply, divide etc.) or logical operation (comparison like equal to, less than, greater than etc.) on data to convert them

5. Five basic operation Into useful information. • Outputting: process of producing useful information or results for user, such as printed report or visual display. • Controlling: directing the manner and sequence in which the above operations are performed.

6. CPU

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

8. In put Unit • For example, data can be entered using keyboard in a manner similar to typing, and this differs from the way in which data is entered through a Scanner. • But computer’s memory is designed to accept input in binary code and hence, all input devices must transform input signals to binary code.

9. In put Unit • In short, an input unit performs following functions, • It accepts instructions and data from outside world. • It converts data and instructions in computer acceptable form. • It supplies the converted instructions and data to computer system for further processing.

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

11. Out Put Unit • In short, an output unit performs following functions, • It accepts the results produced by a computer in a coded form. • It converts these coded results to human acceptable (readable) form. • It supplies the converted results to outside world.

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

13. Storage Unit • In short, storage units holds, • Data and instructions required for processing. • Intermediate results of processing. • Results for output, before they are released to an output device.

14. Memory • A computer's memory can be viewed as a list of cells into which numbers can be placed or read. • Each cell has a numbered "address" and can store a single number. • The computer can be instructed to "put the number 123 into the cell numbered 1357" or to "add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595".

15. Main components of storage unit Primary Storage Secondary Storage

16. Primary Storage It also known as Main memory. It is used to hold: • pieces of program instructions and data, • intermediate results of processing, • recently produced results of those jobs on which the computer is currently working.

17. Primary Storage • CPU can access main memory at a high speed. • But primary storage can hold information only while computer system is on. As soon as the computer turn off, the information held in primary storage is erased. • It has limited storage capacity. • It is very expensive.

18. Secondary Storage It is also known auxiliary storage. It is much cheaper than primary storage and it can retain information even when a computer switches off.

19. Central Processing Unit • Control unit [CU] and Arithmetic Logic unit [ALU] of a computer system are together known as Central processing unit [CPU]. • The CPU is the brain of a computer. • All major calculation and comparisons take place inside the CPU and the CPU is responsible for activating and controlling the operations of other units of Computer.

20. Control unit How does an input device know that it is time for it to feed data to storage unit? How does the ALU know what should be done with the data once they are received? How it is that only result for output are sent to an output device and not the intermediate result? All of this possible due to control unit. Although it does not perform any actual processing on data. It manages and coordinates the entire computer system.

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

22. Arithmetic Logic Unit • The ALU is capable of performing two classes of operations: arithmetic and logic. • Arithmetic operations: addition, subtraction, multiplication and division. • Logical operations compare numbers, letters and special characters, AND, OR and NOT. • Comparison operations test for three conditions, =, <, >

23. If A = B • If B = C • Then A = C is it a correct statement.

24. The Computer’s Core:The CPU and Memory • The transformations are performed by the CPU - the central processing unit or processor. • The microprocessor, which is a silicon chip, is located on the motherboard.

25. ~55 million transistors

27. 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. • 8 bit = 1 Byte.

28. Memory Capacity • 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: Approximately 1015 bytes. • Exabyte: Approximately 1018 bytes.