What is Control Unit ?

The control unit of a computer system manages and coordinates the operations of all the other components of the computer system.

What is ALU ?

The arithmetic logic unit (ALU) of a computer system is the place, where the actual execution of the instructions takes place during the processing operations. The data and instructions, stored in the primary storage before processing are transfered as and when needed to the ALU. No processing is done in the primary storage unit. Intermediate results generated in the ALU are temporarily transfered back to the primary storage until needed later. Hence data may move from primary storage to ALU and back again to storage many time before the processing is over.

What is system ? Why is a computer often referred to as a computer system ?

A system is a group of integrated parts, which have the common purpose of achieving some objectives.

Computer is often referred to as a computer system because it is made up of integrated components (input, output, storage and CPU) which work together to perform steps called for in the program being executed.

Differentiate between the characteristics of Primary and Secondary storage of a computer system.

The primary storage also known as main memory, is used to hold pieces of program instructions and data, intermediate result of processing and recently produced results of processing of the jobs which the computer system is currently working on. These pieces of information are represented electronically in the main memory chips circuitry and while it remains in the main memory, the CPU can access it directly at a very fast speed. However, the primary storage can hold information only while the computer system is on. As soon as the computer system is switched off, the information held in the primary storage disappears. Moreover, the primary storage normally has limited storage capacity, because it is very expensive. The primary storage of modern computer systems is made up of semiconductor devices.

Whereas, the secondary storage also known as auxiliary storage, is used to take care of the limitations of the primary storage. That is, it is used to supplement the limited storage capacity and the volatile characteristic of primary storage. This is because secondary storage is much cheaper than primary storage and it can retain information even when the computer system is switched off. The secondary storage is normally used to hold the program instructions, data and information of those jobs on which the computer system is not working on currently, but needs to hold them for processing later. The most commonly used storage medium is the magnetic disk.

What is Storage Unit ?

The data and instructions which are entered into the computer system through input units, have to stored inside the computer before the actual processing starts. Similarly, the results produced by the computer after processing, must also be kept somewhere inside the computer system, before being passed on to the preserved for ongoing processing. The storage unit of a computer system is designed to cater to all these needs. It provides space for storing data and instructions, space for intermediate result, and space for the final result.

The storage unit of a computer is comprised of the following two types of storage : Primary Storage and Secondary Storage.

what is an input interface ? How does it differ from an output interface ?

The input interfaces transform the input data and instructions fed to the computer through its input devices into the binary codes which are acceptable to the computer.

Whereas, the output interfaces transform the information obtained from data processing, from binary form to human acceptable (readable) form.

What is Output Unit ?

The Output Unit allows the computer system to supply the information, obtained from data processing, to the outside world in human acceptable (readable) form. 

What is Input Unit ?

The Input Unit allows data and instructions to be fed to the computer system from the outside world, in computer acceptable form.

What is CPU ?

The CPU (Central Processing Unit, also known as Processor) is the brain of a computer system. All major calculation and comparisons performed by a computer are carried out inside its CPU. The CPU is also responsible for activating and controlling the operations of other units of computer system. Hence, no other single component of a computer determines its overall performance, as much as the CPU.

Various image of CPU :

What are the five basic operations performed by any computer system ?

All computer systems perform the following five basic operations, for converting raw input data into information, which is useful to their users :

• Inputting: The process of entering data and instructions into the computer system

• Storing : Saving data and instructions to make them readily available for initial or additional processing, as and when required. 

• Processing : Performing arithmetic operations or logical operations on data to convert them into useful information.

• Outputting : The process of producing usefull information or results for the user, such as a printed report or visual display.

•  Controlling : Directing the manner and sequence in which all of the above operations are performed.

What is meant by garbage-in-garbage-out (GIGO) ?

Computer errors caused due to incorrect input data or unreliable programs are often referred to as garbage-in-garbage-out (GIGO).

Differentiate between Data and Information

Data is the raw material used as input to data processing, whereas Information is the processed data obtained as the output of data processing.

Charasteristics of Computer

The power and usefulness of this popular tool are mainly due to its following characteristics :

•  Speed : Computer is so fast that it can perform the given task in a few seconds as compared to man who can spend many months for for doing the same task. It can process millions of instructions per second.

• Accuracy : While doing calculations, a computer is more accurate  than a man. Man can make mistakes in calculation, but a computer does not if it is provided with accurate instructions.
  

• Automatic : Computers are automatic machines because once started on a job they carry on  until the job is finished, normally without any human assistance. However, computer being machines cannot start themselves. They cannot go out and find their own problems and solutions. They have to be instructed.

• High-Memory : A computer has much more memory or storage capacity than human beings. It can store millions of data ans instructions which can retrieved and recalled even after a number of years. This is not possible in case of human beings.

• Dilligence : A computer does not suffer from the human traits of tiredness and boredom. Man will tired and bored while doing millions of calculations, but computer being a machine does this job very efficiently without any tiredness and boredom.

• Versatility : Versatility is one of the most wonderful things about the computer. One moment, it is preparing the result of an examination, the next moment, it is busy preparing electricity bills and in between, it may be helping an office secretary to trace an important letter in seconds. Briefly, a computer is capable of performing almost any task, if the task can be reduced to a series of logical steps.

• No Intelligence / No I.Q. : A computer is a machine and obviously has no intelligence of its own. Each and every instruction must be given to the computer for doing a task. Man has intelligence and it is the man who invented computer and give it all the instructions and logic to work. The main drawback of computer is that it cannot take decision on its own.

• No Feelings : Computers are devoid of emotions. They have no feelings and no instructs because they are machines. Based on our feelings, taste, knowledge and experience, we often taken certain judgments in our day-to-day life. However, computers cannot make such judgments on their own. their judgment is based on the instructions given to them in the form of programs that are written by us.

Why computer also known as a data processor ?

Data comes in various shapes and sizes, depending upon the type of computer application. A computer can store, processes and retrieve data as and when desired. The fact that computers processes data is so fundamental that many people have started calling it a data-processor.

What is data processing ?

The activity of processing data using a computer is called data-processing.
It consist of three sub-activities :

1. Capturing the input data.
2. Manipulating the data.
3. managing the output result.

As used in data processing, information is data arranged in an order and form, which is useful to the people who receive it.

What is Computer ?

The word "computer" comes from the word "computes", which means to calculate. A computer is a fast calculating device that can perform arithmetic operations. Although the computer was originally invented mainly for doing high-speed and accurate calculation. It is not just a calculating device, it can perform any kind of work involving arithmetic and logical operations on data. It gets the data from input device, then process it as per the instruction given and gives the desired information as input.