Components of computer system

 Input Unit:-

🔰 It accepts or reads the instructions and data from the outside world.

🔰 It converts these instructions and data in computer acceptable form.

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

 Output Unit:-

🔰It accepts the result produced by a computer ,which are  in 

coded form and hence cannot be easily understood by us.

🔰It converts these results to human acceptable or a readable form.

  🔰It supplies the converted results to the outside world.

 Storage Unit: - The data and instructions which are entered into the computer system through input units have to be stored inside the computer before the actual processing starts.Similarly, the results produced by the computer after processing must also kept somewhere inside the computer system before being passed on to the output units.

It provides space for storing data and instructions, space for intermediate results, and space for final results.

 Storage Unit of all the computers is comprised of the following two types of storage.

🔰Primary Storage

🔰 Secondary Storage 

Primary Storage:- The primary storage also known as main memory, is used to hold pieces of the program instructions and data, intermediate results of processing  and recently produced results of processing of the jobs, which computer system is currently working on. 

as soon as the computer system is switched off or reset, the information held in the primary storage disappears. Moreover,  the primary storage normally has limited storage capacity because it is very expensive.

 Secondary Storage:- secondary storage also known as auxillary storage.  it is used to take care of the limitations of the primary storage.

 It is much cheaper than primary storage and it can retain information even when the computer system is switched off or reset. Secondary storage is normally used to to hold the program instructions, data and information of these jobs on which the computer system is not working on currently but needs to hold them for processing later.The most  commonly used secondary storage medium is magnetic disk.

Central Processing Unit(CPU): - The functions of any computer system revolves around a central  component as Central Processing Unit(CPU). The CPU which is popularly referred to as the brain of the computer, is responsible for processing the data inside the computer system. It is also responsible for the controlling all the components of the computer system.

 The main operations of the CPU include four  phases.

•  Fetching the instructions from the memory.

•  Decoding the instructions to decide what operations to be performed.

•  Executing the instructions.

•  Storing the result back in the memory. 

This four phase  process is known as CPU cycle

Central Processing Unit consists the following subsystems:-

•  Arithmetic Logic Unit(ALU)

•  Logic Unit(LU)

• Control Unit(CU) 

• Registers

 Arithmetic Unit (AU):-  

🔰 Arithmetic Unit(AU)  is a part  of the CPU that performs arithmetic Operations on data.

🔰Arithmetic operations  can be addition, subtraction, multiplication or division.

🔰The  multiplication and division operations are usually implemented by the the AU  as repetitive  process of addition and subtraction operation respectively.

🔰 Some CPUs  contain AUs  for integer or fixed point operations and real or floating point operations.

🔰AU  take the input in the form of an instruction that contains and opcode, operants And The  format code.

 🔰The opcode specifies the the operation to be performed and operands specify the data on which operation is to be performed. The format code suggest the format of of the operands such as fixed point or floating point.

 

🔰The output is Stored  in a storage register by the  AU.

  

Logic unit (LU):-

🔰 Logic unit is a part of the CPU that performs logical operations on the data. it performs 16  different types of logical operations.

🔰 The various logical operations on data include greater than, less than, equal to ,not equal to, Shift left, shift right etc.

 🔰Logic Unit makes use of various logic gates  such as AND, OR,NOR etc for performing the logic operations on the data.

Control Unit(CU):- 

🔰Control Unit is an important component of the CPU that controls the flow of the data and information. It maintains the sequence of operations being performed by the CPU. It fetches  an instruction from the storage area, take out the instruction and transmits the corresponding signals to the AU or LU  and storage registers.

🔰CU  guides the AU and LU  about the operations that are to be performed  and also suggests input- output devices to which the the data is to be communicated.

🔰CU  uses a program counter register for retrieving the matched instruction that is to be executed.

🔰 It also uses a status register for handling conditions such as overflow of data.

 Registers:- Central Processing Unit contains a few special purpose, temporary storage units known as  registers.They are high speed memory locations used for holding instructions, data and intermediate results that are currently being processed. A processor  can have different types of registers to hold different types of information.

🔰 Program Counter to keep track of the next instruction to be executed.

🔰 Instruction Register to hold instructions to be recorded by the control unit.

🔰 Memory Address Register to hold the address of the next location in the memory to be accessed.

 🔰Memory Buffer Register for storing data received from or sent to CPU.

🔰 Accumulator for storing results produced by arithmetic and logic units.

 Many computers  uses additional registers for implementing various other requirements. The number and size of  register therefore vary from processor to processor. An effective  implementation of  registers  can increase considerably  the speed of of the processor.