Important Short Notes On ICT For All Competitive Exams -Part -1

Computer:Computer is an electronic device which is used to store the data, as per given instructions it gives results quickly and accurately.

Main characteristics of a computer:
A computer is a programmable machine. The two main characteristics of a computer are:
  1. It responds to a specific set of instructions in a well-defined manner. 
  2. It can execute a pre-recorded list of instructions or a program.
Basic Concepts of Computer:
Data : Data is a raw material of information.
Information : Proper collection of the data is called information.

Characteristics of Computer:
The characteristics of computers that have made them so powerful and universally useful are speed, accuracy, diligence, versatility and storage capacity. Let us discuss them briefly.
  • SPEED : In general, no human being can compete to solving the complex computation, faster than computer.
  • ACCURACY : Since Computer is programmed, so what ever input we give it gives result with accuratly.
  • STORAGE : Computer can store mass storage of data with appropriate formate.
  • DILIGENCE : Computer can work for hours without any break and creating error.
  • VERSATILITY : We can use computer to perform completely different type of work at the same time.
  • MEMORY : It can save and store a large collection of data for us.
Computer and its components:
  1. Central Processing Unit (CPU): The ‘brain’ of the computer, the component that actually executes instructions.
  2. Memory : It enables a computer to store, at least temporarily, data and programs.
  3. Input device : Usually a keyboard or mouse is used to read data and programs into the computer.
  4. Output device: A display screen, printer, etc. that lets you see what the computer has accomplished.
  5. Mass storage device: It allows a computer to permanently store large amounts of data. Common mass storage devices include disk drive and tape drive.
Computer Software : Software is a logical program to handle/solve the complex problem.
Types Of Software:
  • System Software : This is special type of software which is responsible for handle the whole computer system.
  • Application Software : This is special type of software which is used to solve a particular problem.
  • Embeded Software : This type of software embeded with hardware to do a specific type of job.
  • Proprietary Software : In general, this type of software require to purchase to use that particular software for the some time or single user as per conditioned by the vendor of that particular software.
  • Open Source Software : This type of software may be freely available and can not be use in commercially. We can modify, and use it under the same license.
Functions and Components of a Computer:

To function properly, the computer needs both hardware and software.A computer does mainly the following four functions:

1. Receive input: Accept data/information from outside through various input devices like the keyboard, mouse, scanner, etc.
2. Process information: Perform arithmetic or logical operations on data/information.
3. Produce output: Communicate information to the outside world through output devices like monitor, printer, etc.
4. Store information: Store the information in storage devices like hard disk, floppy disks, CD, etc.

Computer Languages
Machine Level Language: This is low level programming language. Computer or any electronic device only understand this language. i.e. Binary number i.e 0 and 1.
Assembly Level Language: This is a low level programming language which is converted into executable machine code by a utility programmer referred to as an assembler.
High Level Language: High level language is a programming language which is easily understandable/readable by human.
Interpreter: This is a converter which converts high level language program to low level language program line by line.
Compiler: This is also a converter which converts whole high level language program to low level language program at a time.

Number System:
  1. Binary Number System : It has only base 2 i.e 0 and 1
  2. Octal Number System  : Base of octal is 8 i.e. 0, 1, 2, 3, 4, 5, 6, 7
  3. Decimal Number System : Base of Decimal is 10 i.e. 0 1 2 3 4 5 6 7 8 9
  4. Hexadecimal Number System : Base of this number system is 16 i.e. 0 1 2 3 4 5 6 7 8 9 A B C D E F
How the CPU and Memory work?

The working of the CPU and memory involves different steps for different tasks. let us consider steps involved in the multiplication of two numbers.
Step 1: The control unit recognizes that the program has been loaded into the memory. It begins to execute the first step in the program.
Step 2: The program tells the user, "Enter 1st Number".
Step 3: Suppose the user types the number 100 on the keyboard. An electronic signal is sent to the CPU.
Step 4: The control unit recognizes this signal and routes the signal to an address in memory - say address 7.
Step 5: After completing the above instruction, the next instruction tells the user,"Enter 2nd Number."
Step 6: Let us assume that the user types the number 4 on the keyboard. An electronic signal is sent to the CPU.
Step 7:  Now the control unit recognizes this signal and routes it to memory address 8.
Step 8:The next program instruction is executed - "Multiply 1st and 2nd Numbers."
Step 9: To execute this instruction, the control unit informs the ALU that two numbers are coming and the ALU is to multiply them. The control unit next sends to the ALU a copy of the contents of address 7 (100) and address 8(4).
Step 10: ALU performs the multiplication : 100 × 4 = 400
Step 11:  The control unit sends a copy of the multiplied result (400:) back to memory to store it in address 9.
Step 12: The next program instruction is executed : "Print the Result."
Step 13: To execute this instruction, the control unit sends the contents of the address 9 (400) to the monitor.
Step 14:  Monitor displays the value 400.
Step 15: Final instruction is executed: "End". The program is complete.

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