Computer Architecture:-
The computer architecture deals with the functional behavior of a computer system as viewed by a programmer. It can also be described as the logical structure of the system unit that housed electronic components. The computer architecture forms the backbone for building successful computer systems. the first computer architecture was introduced in 1970.
Components of Computer:-
A computer consists of following three main components:-
1.Input/Output(I/O Unit)
2.Central Processing Unit(CPU)
3.Memory Unit
Note:-
System unit is a metal or plastic case that holds all the physical parts of the computer.
The components that process data are located in it.
1.Input Unit:-
The computer accepts coded information through input unit by the user. It is a device that is used to give required information to the computer.
e.g. Keyboard, mouse etc.
An input units perform the following functions:-
i. It converts these instructions and data in the computer in acceptable format.
ii. It accepts the instructions and data from the user.
iii. It supplies the converted instructions and data to the computer system for further processing.
2.Output Unit:-
This unit sends the processed results to the user. It is mainly used to display the desired result to the user as per input instruction.
e.g. Monitor, printer etc.
An output units perform the following functions:-
i. It converts these coded results to human acceptable format.
ii. It accepts the result produced by the computer which are in coded form and hence cannot be easily understood by the user.
iii. It supplies the converted results to the user.
3.Central Processing Unit:-
It consists of a set of registers, arithmetic logic unit and controls unit, which together interpret and execute instructions in assembly language.
The primary functions of the CPU are as follows:-
i. The CPU transfers instructions and input data from main memory to registers, i.e. internal memory.
ii. The CPU executes the instructions in the stored sequence.
iii. When necessary , CPU transfers output data from registers to main memory.
Central Processing Unit is often called the brain of the computer system. The CPU is fabricated as a single Integrated Circuit (IC) and it is also known as microprocessor.
A CPU controls all the internal and external devices and performs arithmetic and logic operations.
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The CPU consists of following main components:-
- Arithmetic Logic Unit:- ALU contains the electronic circuitry that executes all arithmetic and logical operations on the available data. It uses registers to hold the data that is being processed.
Most ALU performs the following operations in a computer:-
i. Logical operations(AND, NOT, OR, XOR etc.)
ii. Comparison operator (=, <, >, >=, <= etc.)
iii. Arithmetic operations such as addition, subtraction, multiplication, division etc.
Note:-
Registers:- Registers are used to quickly accepts , store, transfer data and instructions that are being used immediately by the CPU. These registers are the top of the memory hierarchy and are the fastest way for the system to manipulate data. The number and size of registers vary from processors to processors.
- Control Unit:- Control Unit coordinates with the input and output devices of a computer. It directs the computer to carry out stored program instructions by communicating with the ALU and the registers. The basic functions of control unit is to fetch the instructions stored in the main memory, identify the operations and the devices involved in it and accordingly generate control signal's. It organises the processing of data and instructions.
- Memory Unit:- Memory unit is responsible to store programs or data on a temporary or permanent basis. It has a primary memory which is called main memory and secondary memory is also called auxiliary memory. The input data which is to be processed is brought into the main memory of a computer system before processing
Another kind of memory is referred to as secondary memory of a computer. This unit does not deal directly with the CPU in a computer system. This unit is used to permanently store data and programs in the form of output in the computer system.
What is Motherboard:-
The main circuit board contained in any computer system is called motherboard. Motherboard is also known as the main board or logic board or system board. All the electronic devices and circuits of computer systems are attached to this board like CPU, ROM, RAM, expansion slots, PCI slots and USB ports. It also includes controllers for devices like DVD drive, hard drive, mouse and keyboard etc. In some other words, motherboard makes everything in a computers system work together.
A motherboard is one of the most essential parts of a computer system.
It is the brain of the computer system. It holds together many of the crucial components of a computer, including the central processing unit (CPU), memory and connectors for input and output devices. Thin layers of copper or aluminum foil, referred to as traces, are printed onto this sheet. These traces are very narrow and form the circuits between the various components.
A motherboard contains a number of sockets and slots to connect the other components.
Components of Motherboard:-
The various components of motherboard are as follows:-
i. CMOS Battery
ii. Fan
iii. BIOS Chip
iv. Processor Chip
v. Buses
vi. SMPS
vii. Expansion Slot
viii. PCI Slot
- Interconnection of Units in a Computer system:-
In a computer system the CPU sends the data or instructions and information to the components inside the computer as well as to the peripheral devices attached to it. A Bus is a s set of wires used for interconnection where each wire can carry one bit of data.
In other words bus is a set of electronic signal pathways that allows information and signals to travel between components inside or outside of a computer.
A Bus can be divided into two types:
1.Internal Bus:
This bus connects components inside the motherboard like CPU and system memory. Internal bus is also called system bus.
System bus includes the following buses:-
i. The command to access the memory or the I/O devices is carried by the control bus.
ii. The address of I/O devices or memory is carried by the address bus. The data to be transferred is carried by the data bus.
2.External Bus:-
It connects the different external devices like peripherals, expansion slots and I/O ports. External bus is also called expansion bus.
Instruction Cycle:-
Instruction cycle represents the sequence of events that takes place as an instructions is read from memory and executed.
Diagram of Instruction Cycle
Fetch => Decode => Execute => Store
A simple instruction cycle consists of the following steps:-
1.Fetching:- It fetch the information from the memory.
2.Decoding:- It decodes the instruction for operation.
3.Executing:- It executes the instructions.
4.Storing:- It also stores the data in the memory.
Instruction Format:-
In computer system, computers understands instructions only in terms of 0 and 1, which is called the machine language. A computer program is a set of instructions that describe the steps to be performed for carrying out a computational task. The processor must have two inputs: instructions and data. The instructions tell the processor to what actions are needed to perform this task. An instructions is further divided into two parts: i. Operation(OP Code) and ii. Operand.
Notes:-
Sockets' are the connecting points of chip on the motherboard.
- Pipelining:- It improves the execution speed by putting the execution steps of several instructions into parallel.
- Machine Cycle:- It is defined by the time, that takes to fetch two operands from registers and performs ALU operation and stores the result in a register of a computer system.
Some useful terms related to to computer architecture:-
Q. What is UPS(Uninterruptable Power Supply):-
Ans. It is an electrical device that provides emergency power to a load when the input power source or main power source fails.
Q. What is DMA(Direct Memory Access):-
Ans. It is a method that allows an I/O devices to send or receive data to or from the main memory.
- The speed of processor is measured in millions of cycles per second or Megahertz(Mhz) by clock speed.
- An uniform interval of CPU time allocated for use in performing a task is called time slice.
Q. What is Buffer:-
Ans. It is a temporary storage where register holds the data for future execution.
Q. What is Accumulator:-
Ans. It is a register in a CPU which intermediate arithmetic and logic results that are stored.
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