Computer programs are also usually referred to as computer software. A Computer Program is a set of instructions given to the computer to solve a particular problem. The computer program specifies a sequence of operations that the computer will perform. System software and application software are the two main types of computer software.
Computer Software is further divided into two major categories:
System Software refers to the programs that are responsible for controlling and managing the actual operations of computer hardware. Generally, system software consists of an operating system and some fundamental utilities such as disk for matters, Managers, display managers, user authentication (login), and network control Software.
Application Software is used to accomplish tasks specified by the user. Application May consists of a single program, such as an image viewer or a collection of Programs (called software package) that work together to accomplish a task. e.g.
Word processors, spreadsheets, databases, etc.
Organization of Computer
A computer performs the following five major functions:
In order to perform above-mentioned operations; the computer system is divided
Into three units. These are
He Central Processing Unit (CPU) is generally referred to as the brain of the
Computer. The primary work of CPU is to convert data from Input, process the data and output in useful information that can be used by either user or other
Programs. The central processing unit (CPU) is a highly complex set of electronic Circuitry that Executes program Instructions. It is like a really fast Calculator that has the ability to recall Numbers from various locations in Memory, perform arithmetic and logical operations with them, such as addition Or multiplication, and then store the Results.
All computers must have a Central processing unit. As Figure 2.3 shows, the central processing unit consists of two main parts: The control Unit, arithmetic, and logic unit. Each part Has a specific function.
The Arithmetic and Logic Unit (ALU) consists of electronic circuitry that Executes all arithmetic and logical operations. The arithmetic and logic unit can perform the following operations, like:
A logical operation is usually a comparison of numbers, letters, or special characters. The computer can then take action based on the result of the comparison. This is a very important capability. It is by comparing that a computer is able to tell, For example, whether there are available seats on the train, whether mobile phone Customers have exceeded their pre-paid credit limits, etc.
Logical operations can test for three conditions:
Less-than condition: The computer compares values to determine if one Less than another. For example, if the hours a person worked this week Are less than 35, then some fine is deducted from his salary.
Greater-than condition.
The computer determines if one value is greater Than another. For example, if the hours a person worked this week are Greater than 40, then he gets a bonus for working overtime.
The Control Unit consists of circuitry that generates signals to direct the entire Computer system to carry out or execute the programs. The control unit itself does not Execute program instructions; rather, it directs other parts of the system to do so. The Control unit must communicate with the arithmetic and logic unit, memory and other
Of computer system.
It also controls the flow of information through the processor and coordinates Activities of the other units. This unit also provides clock pulses. Clock pulses are In addition to the ALU and CU (Control Unit), the processor has a number of Locations to store information that is currently being processed.
These are Registers. These are temporary storage areas for instructions or data. Registers Managed by the control unit to accept, hold, and transfer instructions or data and Arithmetic or logical comparisons at high speed.
The CPU must be able to communicate with all devices. The devices are Together by a communications channel called a bus. A ‘bus is composed of “f communication lines or wires. It is used to move a large number of bits in the
Electrical pulses from a specified source to a specified destination. The Bus is the common path that is used to send /receive data and commands To/from CPU and memory and all input/output devices. It is also used to send/receive data from secondary storage. The capacity of a bus depends upon the number Of data lines it contains. Bus with 16 lines can carry 16-bits (2 Bytes) at a time where Bus with 32 lines can carry 32-bits (4 Bytes) at a time and so on. There are three
The most common bus is the data bus. A data bus carries data. It is The electrical path that connects the central processing unit (CPU), memory, input/output devices, and secondary storage devices. The bus contains a parallel group of lines. The Number of lines in the bus affects the speed at which the data travels between Different components. Just like the number of lanes on a motorway affect the amount Of the number of lanes on road means more cars can pass through it.
More lines are present on the bus, it can carry more data. E.g. a bus with 16 lines c Carry 16 bits (2 bytes) and a bus with 32 lines can carry 32 bits (4 bytes) of data.
Busses are designed in such a way that they can communicate with the Components in an efficient way. In old computers, buses were able to carry only on Byte of data but with the improvement in technology, the busses present in today’s Computer can carry multiple bytes at one time thus improving the speed a Performance of the computers.
An address bus carries address information. It is a set of wires similar to the Data by but it only connects the central processing unit (CPU) and memory. Whenever The processor needs data from the memory, it places the address of data on the Address Bus. The address is carried to the memory where the data from the requested address
Is fetched and placed on the data bus. The data bus carries it to the processor. The reason for the importance of address bus is the number of lines in The address bus determines the maximum number of memory addresses if an address Bus has 8 lines, the maximum number of memory locations that can be addressed Are 28 256. Today’s computers have 32-bit address lines so they can access 4GB (GigaByte) of memory.
The control bus carries control information from the control unit to the other Units. The control information is used for directing the activities of all units. The control unit directs the transfer of data to the ALU from the memory. This data the functioning of other
Units e.g.. Input/output devices, secondary storage, etc.,
Computer storage is also referred to as computer memory. The computer IS used to store programs and data, There are two types of computer memory.
The main memory is accessible directly by the processing unit. RAM is an example of the main memory. As soon as the computer is switched off the contents of the Memory are lost you can store and retrieve data much faster with main memory Compared to secondary memory, the reason is that the main memory is present on Motherboard. Secondary memory such as floppy disks, magnetic disk. Etc. is Located outside the motherboard. Main memory is more expensive than secondary memory. That is why the size of the main memory is less than that of secondary memory.
As the storage capacity of the main memory is limited and often it is Necessary to store hundreds of millions of bytes of data for the CPU to process, 2-before, additional memory is required in all the computer systems. This memory is Secondary memory or secondary storage.
A computer is only useful when it is able to communicate with the external environment. When we work with the computer, we feed data and instructions Sough some devices to the computer. These devices are called input devices, Similarly computer, after processing data and instructions, gives output through some
Devices called output devices. Input/output devices are also known as peripheral devices.
A port can be defined as a socket that enables an external device such as a printer to be attached to the computer”, All communication between a computer and external devices are the result of properly connected ports. On every computer, a port’s Connectors are attached to a motherboard. There are three basic types of ports:
‘Today’s computers have all these types of ports with each type doing a different Function.
A serial port allows a serial hardware device to communicate with the Computer by transmitting one bit of information at a time. Serial devices, such a Mouse, modems, and keyboards do not require fast data transmission rates. Serial Ports often referred to as communications (COM) ports. It is an external port on thx
Back of the computer that attaches directly to the PC’s motherboard. These ports were One of the early ports put on computers. Older serial ports also used 25-pin Connector for their serial port, but most new computers with serial ports feature on Nine pins.
Parallel portlets an external parallel device communicates with the computer by transmitting more bits (Such as 8 or 25) of data at a time, therefore, it is much faster Than a serial port. Most devices that send or receive large amounts of data, such as Printers and scanners, use parallel ports. Parallel ports are often referred to as Line Printer (LPT) ports. The parallel port is the largest port on the rear of your PC, Comprising 25 lines that include 17 signal lines and eight ground lines.
USB (Universal Serial Bus) is€ a plug-and-play hardware interface for Peripherals such as the keyboard, mouse, joystick, scanner, printer, and modem. USB Has a maximum bandwidth of 12 Mbits /sec and up to 127 devices can be attached. With USB, a new device can be added to the computer without having to
Add an adapter card. It typically is located at the back PC and looks as in the following (sometimes positioned vertically). Sometimes it has the USB symbol next to it.
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