What is computer ?

Computer Means it is an electronics device which can process the input and gives desired output. It also stores data for further processing. Computer works with 0's & 1's.

(Here am specifying another way of definition for computer to understand more easy way.) A computer is a machine that can be programmed to manipulate symbols. Its principal characteristics are:

-It responds to a specific set of instructions in a well-defined manner.

-It can execute a pre-recorded list of instructions (a program).-It can quickly store and retrieve large amounts of data.

Therefore computers can perform complex and repetitive procedures quickly, precisely and reliably.

Modern computers are electronic and digital. The actual machinery (components of computer) is called hardware. And use this hardware precisely & reliably we use something called software. Below is the basic diagram for computer.

Central processing unit (CPU): In a PC, the central processing unit (CPU) is the primary control device for the entirecomputer system. The CPU is technically a set of components that manages all the activities and does much of the “heavy lifting” in a computer system. The CPU interfaces, or is connected, to all of the components such as memory, storage, and input/output

(I/O) through communications channels called busses. The CPU performs a number of individual or discrete functions that must work in harmony in order for the system to function. Additionally, the CPU is responsible for managing the activities of the entire system. The CPU takes direction from internal commands that are stored in the CPU as well as external commands that come from the operating system and other programs.

Control Unit :

The control unit shown in Figure is primarily responsible for directing all the activities of the computer. It also manages interactions between the other components in the computer system. In addition, the control unit contains both hardwired instructions and programmed instructions (called microcode or microprograms) to perform operations. An example of an instruction might be the command to fetch information from memory. In older systems, the control unit would be a large number of integrated circuits on a circuit card. On a microprocessor based system, the control unit is part of the microprocessor.

Memory:

Computer memory provides the primary storage for a computer system. The CPU will

typically have internal memory (embedded in the CPU) that is used for operations and external memory located on the system or motherboard. The most common general types are Random Access Memory (RAM) and Read-Only Memory (ROM). The important consideration about memory is that the control unit is responsible for controlling usage of all memory. A more detailed discussion about memory occurs in the section on CPUs.

ALU:

The arithmetic logic unit (ALU) is responsible for all logical and mathematical operations in the system. The ALU receives instructions from the control unit. The ALU can take information from memory, perform computations and comparisons, and then store the results in memory locations as directed by the control unit. An additional type of ALU, called a floating point unit (FPU) or coprocessor, which performs specialized functions such as division and large decimal number operations, is frequently used. Most modern microprocessors include an FPU processor as part of the microprocessor.

Input/Output :

The input device is the conduit through which data and instructions enter a computer. i,e. keyboard and mouse

Output devices are Monitor, printer, or other device that lets you see what the computer has accomplished.

Controllers:

The CPU also contains a number of interfaces or controllers to access devices and busses. One of the primary functions of a controller is to free up the time of the control unit by performing routine or clearly identified tasks. A typical microprocessor will have controllers interface to slow-speed devices such as serial data connections, high-speed interfaces connect to a computer bus, and connections to dedicated registers contain and report status. These controllers will also typically interface to other controllers on a bus for specific types of operations. The details of this are not important except that they have a huge impact on system performance. The more work that the CPU can give to a controller, the less work the control unit will have to be concerned with.