Components of Computer
- Input/Output (I/O) Unit
- Central Processing Unit
- Memory Unit
Input Unit
- It accepts the instructions and data from the user.
- It converts these instructions and data into a computer in an acceptable format.
- It supplies the converted instructions and data to the computer system for further processing.
Output Unit
- It accepts the results produced by the computer which are in coded form and hence cannot be easily understood by the user.
- It converts these coded results to a human acceptable form.
- It supplies the converted results to the user.
Central Processing Unit (CPU)
- The CPU transfers instructions and input data from main memory to registers, i.e. internal memory.
- The CPU executes the instructions in the stored sequence.
- When necessary, the CPU transfers output data from registers to the main memory.
The CPU consists of the following main sub-systems
Arithmetic Logic Unit (ALU)
- Logical operations (AND, NOT, OR, XOR).
- Arithmetic operations (addition, subtraction, multiplication, and division).
- Bit-shifting operations (shifting or rotating a word by a specified number of bits to the left or right with or without sign extension).
- Comparison operations (=, <, < =, >, > =)
Registers: These are used to quickly accept, store and 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 processor to processor.
Control Unit (CU)
CU 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. It organizes the processing of data and instructions.
The basic function of the control unit is to fetch the instruction stored in the main memory, identify the operations and the devices involved in it, and accordingly generate control signals.
Microprocessor: It is the controlling element in a computer system and is sometimes referred to as the chip. Microprocessor is the main hardware that drives the computer. It is a large Printed Circuit Board (PCB), which is used in all electronic systems such as computer, calculator, digital system, etc. The speed of CPU depends upon the type of microprocessor used.
- Intel 4004 was the first microprocessor made by Intel in 1971 by scientist Ted Hoff and engineer Frederico Faggin.
- Some of the popular microprocessors are Intel, Intel core i7, Dual core, Pentium IV, etc.
Memory Unit
This unit is responsible to store programs or data on a temporary or permanent basis. It has primary memory (main memory) and secondary memory (auxiliary memory).
The input data which is to be processed is brought into the main memory before processing.
Another kind of memory is referred to as the secondary memory of a computer system. This unit is used to permanently store data, programs, and output. This unit does not deal directly with the CPU.
Motherboard
The main circuit board contained in any computer is called a motherboard. It is also known as the main board or logic board or system board or planar board. All the other electronic devices and circuits of the computer system are attached to this board including CPU, ROM, RAM, expansion slots, PCI slots, and USB ports. It also includes controllers for devices like the hard drive, DVD drive, keyboard, and mouse. In other words, the motherboard makes everything in a computer work together.
Components on Motherboard
Various components on the motherboard are as follows
- CMOS Battery
- BIOS Chip
- Fan
- Expansion Slot
- SMPS
- PCI Slot
- Processor Chip
- Buses
Interconnection of Units
CPU sends data, instructions, and information to
the components inside the computer as well as to
the peripheral devices attached to it.
A bus is a set of wires used for interconnection,
where each wire can carry one bit of data.
In other words, the bus is a set of electronic signal
pathways that allows information and signals to
travel between components inside or outside of a
computer. A computer bus can be divided into two types
- Internal Bus: The internal bus connects
components inside the motherboard like the CPU and system memory. It is also called the
system bus. The internal bus includes the following buses
- The command to access the memory or the I/O devices is carried by the control bus.
- 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.
- External Bus: It connects the different external devices; peripherals, expansion slots, I/O ports, and drive connections to the rest of the computer. It is also referred to as the expansion bus.
UPS (Uninterruptible Power Supply), is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails.
Buffer is temporary storage where the register holds the data for further execution.
An accumulator is a register in a CPU in which intermediate arithmetic and logic results are stored.
A uniform interval of CPU time allocated for use in performing a task is known as a time slice.
The speed of the processor is measured in millions of cycles per second or megahertz (MHz) by clock speed.
DMA (Direct Memory Access) is a method that allows an input/output device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations.
Instruction Cycle
It represents the sequence of events that takes place as instruction is read from memory and executed.
A simple instruction cycle consists of the following steps
- Fetching the instruction from the memory.
- Decoding the instruction for the operation.
- Executing the instruction.
- Storing in memory.
In the above steps, steps 1 and 2 instructions are the same and known as fetch cycle, and steps 3 and 4 instructions are different and known as execute cycle.
Instructions Format
The computer understands instructions only in terms of 0’s and 1’s, which is called machine language. A computer program is a set of instructions that describes 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 what actions are needed to be performed on the data. Instruction is further divided into two parts; operation (op-code) and operand.
The op-code represents an action that the processor must execute and the operand defines the parameters of the action and depends on the operation.
Machine cycle is defined by the time, that takes to fetch two operands from registers and perform ALU operation, and store the result in a register.
Pipelining improves execution speed by putting the execution steps of several instructions into parallel. It is called implement instruction prefetch.
Sockets are the connecting points of chip on the motherboard.
